[volt-nuts] 3457A battery replacement at Keysight - not as cheap as I thought it would be!

[Dr. David Kirkby]

Last year I went down to Keysight for a course, and got a tour of their cal
labs. I spoke to the person showing us around about the 3457A battery. He
said if the battery was less than £35 or so, it could be replaced free of
charge when the instrument was calibrated.

So despite my 3457A's battery must be on its last legs, I decided not to
bother replacing it, as I thought Keysight would do it free. The other more
serious reason is that I can't seem to find a suitable battery in the UK.
This from Mouser

The Panasonic BR-2/3AE5SPN

https://www.digikey.com/product-detail/en/panasonic-bsg/BR-2-3AE5SPN/P226-ND/61161

looks like it will do the job, and is less than $6 in the USA, but I can't
get one in the UK.

Anyway, my meter was sent to Keysight for a technical evaluation, and today
I received a quote

* Keysight calibration with uncertainties £140 (GBP)
* Repair (time and material) £289.35 (GBP)
* Total £429.

All + 20% VAT

So far from being free, they now want a serious amount of money to replace
the battery! It's more than a third of the cost of a brand new 6.5 digit
meter, with the complete battery and calibration costing more than 50% of
the price of a new 6.5 digit meter.

With eBay being a counterfeiters paradise, I will not buy a battery from
there. None of the UK companies I find have something that looks suitable.
I might try to find someone in the USA who will post me one by surface
mail. That should avoid all the problems with air transport of lithium
batteries.

Dave
___
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

[volt-nuts] 3457A (6.5 digit multi-meter). Is it best to keep it on?

[Dr. David Kirkby]

I have a 3457A which does not get a lot of use, but it has not been
calibrated for years, and I need to get it calibrated as I need to make
some measurements of greater accuracy than usual. The 3457A is scheduled to
go to Keysight a week from today. I'm wondering if its best to keep it
powered up until then, to let the reference stabilize somewhat. Or it is a
bit late for that now?

I have asked Keysight to change the battery - I'm led to believe that
Keysight will do that as part of the calibration unless the battery is
particularly expensive.

When I last looked, I could not find a suitable battery in the UK, and
those in the US could not be shipped here. But that was a few years ago, so
maybe things are different.

Dr David Kirkby Ph.D C.Eng MIET
Kirkby Microwave Ltd
Registered office: Stokes Hall Lodge, Burnham Rd, Althorne, CHELMSFORD,
Essex, CM3 6DT, United Kingdom.
Registered in England and Wales as company number 08914892
http://www.kirkbymicrowave.co.uk/
Tel 01621-680100 / +44 1621-680100
___
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

Re: [volt-nuts] EU3458A - what appears to be a 3458A for sales in the European Union only.

[Dr. David Kirkby]

On 14 May 2018 at 13:01, Dr. David Kirkby <drkir...@kirkbymicrowave.co.uk>
wrote:

> I'm puzzled why option 002, an upgrade of memory to 128 kb, is still an
> option one has to pay for. With the cost of RAM what it is now, I'm
> suprised the memor is not not standard. Perhaps the only way Keysight can
> provide 128 kb is to use old chips, as new ones are too large!
>
>
Sorry, I mean option 001.  Option 002 is the higher stability 4 ppm/year
reference, which naturally costs more.

Dave
___
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

[volt-nuts] EU3458A - what appears to be a 3458A for sales in the European Union only.

[Dr. David Kirkby]

This struck me as a bit odd - an EU3458A 8.5 digit multimeter. I thought at
first that perhaps it had been re-engineered to use lead-free solder, but
on reading the description, that's not the case.

https://www.keysight.com/en/pd-2831253-pn-EU3458A/digital-
multimeter-8-digit-for-eu-sales-only?nid=-536902435.1217937=GB=eng

The Keysight website says

===
Notice for European Union Customers: This non-RoHS product has been placed
on the market prior to the compliance deadline and continues to be made
available on the EU market under product numbers EU3458A / EU3458AX. Please
contact Keysight Sales for quotation and ordering. Keysight will continue
service and support for this product throughout worldwide support life.
=

I can't see what is the point of giving it a new part number. But at least
is dismisses some of the myths that used 3458As would go up in value in the
EU, since it would be impossible to buy a new one.

I'm puzzled why option 002, an upgrade of memory to 128 kb, is still an
option one has to pay for. With the cost of RAM what it is now, I'm
suprised the memor is not not standard. Perhaps the only way Keysight can
provide 128 kb is to use old chips, as new ones are too large!

Dr David Kirkby Ph.D C.Eng MIET
Kirkby Microwave Ltd
Registered office: Stokes Hall Lodge, Burnham Rd, Althorne, CHELMSFORD,
Essex, CM3 6DT, United Kingdom.
Registered in England and Wales as company number 08914892
http://www.kirkbymicrowave.co.uk/
Tel 01621-680100 / +44 1621-680100
___
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

Re: [volt-nuts] Two 4338B high resistance meters fail on the same range - Keysight can't adjust EEPROM of either.

[Dr. David Kirkby]

On Wed, 2 May 2018, 18:28 Charles Steinmetz,  wrote:

> Dave wrote:
>
> > This has certainty got me thinking about what might be happening,
> although
> > the fact Keysight have said they can't update the EEPROM, suggests they
> > have the software to do it.
>
> Or does it mean they have lost the software to do it?  Does the cal
> certificate have "as received" and "as adjusted" error readings for
> other ranges?  If not, perhaps they adjusted nothing, which would leave
> open the possibility that they simply cannot adjust these meters anymore
> due to lack of software.
>
> Best regards,
>
> Charles


I spoke to someone at Keysight (UK) yesterday who confirmed they do have
the software to update the EEPROM.  I have asked Keysight if they can
confirm they have the latest software as it crossed my mind that the latest
firmware, which both instruments have, may require later software than what
Keysight UK have.

They believe the fault is the CPU board, but if they fit another CPU board,
and it does not fix the problem, I still would need to pay for the CPU
board. Then they would suspect the ammeter board - which is very expensive.

Apparently Keysight UK have asked the USA for advice, but have not received
anything - or at least not anything useful.  Maybe I should suggest they
try Malaysia, as I believe that's where the last ones were made.

I seem to be between a rock and a hard place.

1) I am not confident Keysight UK can calibrate this properly, despite them
saying they have calibrated two others recently.

Several things, such as the inability to give me the uncertainties, does
not inspire confidence.

2) I don't believe that the CPU board is faulty, given two instruments are
displaying the same problem. Whilst I would not paying for a new CPU board
if it fixed the problem, I am not keen to pay if does not resolve the
issue.

3) The user can save settings to the EEPROM. That works.

4) The service manual I have does not go to component level. So changing
the sensitivity of the current to voltage converter in hardware, rather
than software is not practical.

5) Sending these instruments for calibration only to have them fail each
time, gets expensive.

Currently this instrument is supported by Keysight, but from the end of the
year it will become obsolete.

The only good thing is I have a couple of 4349Bs which are different models
if Hugh resistance meters, which use the same CPU board. One of the
instruments has a new (Agilent, not HP branded CPU), which means it would
be newer than either of the others.

If anyone has any ideas how to proceed, pleasure suggest them.

PS I am looking to find a suitable resistor to allow me to produce the 10
nA the same way as Keysight do (10 V and 100 M ohm). The best resistor I
have found to date is 0.1% which is not really good enough to test a meter
which should have an uncertainty close 0.6% (I think 0.603% from memory). I
don't have the 3458A the 4339Bs service manual calls for, but I have a
3457A which should be adequate to measure 10V sufficiently accurately for
this purpose. I am going to send the 3457A to Keysight for calibration as
soon as Keysight can do it.

Dave.
___
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

Re: [volt-nuts] Ayrton Shunt does double duty.

[Dr. David Kirkby]

On Mon, 30 Apr 2018, 20:02 ,  wrote:

> Leeds and Northrup Ayrton Shunt box Model 2664.
>
> Modified to do double duty as a precision resistor standard.


I must admit I don't know what the purpose of the original unit is. Perhaps
as part of a bridge given the galvanometer connections.

I know when I was looking to check out my HP 4284A precession LCR meter
(basic uncertainty of 0.05%) I was able to buy some 0.005% resistors in
some values. I think if trying to build a precision resistance box I would
look for resistors better than the 0.03% in there.

I wonder if you could go to much lower resistance values if you used the
galvanometer connections as sense wires. But maybe you are using it in a
way I don't understand. I only have my mobile phone now, so are not going
to search the web for more information.

Dave.
___
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

Re: [volt-nuts] Two 4338B high resistance meters fail on the same range - Keysight can't adjust EEPROM of either.

[Dr. David Kirkby]

On 2 May 2018 at 18:27, Charles Steinmetz  wrote:

> Dave wrote:
>
> This has certainty got me thinking about what might be happening, although
>> the fact Keysight have said they can't update the EEPROM, suggests they
>> have the software to do it.
>>
>
> Or does it mean they have lost the software to do it?  Does the cal
> certificate have "as received" and "as adjusted" error readings for other
> ranges?  If not, perhaps they adjusted nothing, which would leave open the
> possibility that they simply cannot adjust these meters anymore due to lack
> of software.
>
> Best regards,
>
> Charles


I don't have a cal certificate - only a report of how it was received

http://www.kirkbymicrowave.co.uk/tmp/Measurement_report_As_received_1-9957310275-1.pdf

and an email saying it can't be updated.



Hi David,



We’ve a High Resistance Meter for calibration, but the instrument is faulty.



Model: 4339B

Serial Number: JP1KD01746

Service Order: 1-9957310275



The calibration has failed, I’ve attached a copy of the calibration
results.

Automated adjustments were attempted. Source Voltage Adjustment could be
completed ok, but the Ammeter Adjustment could not be completed.

I’ve passed the instrument to our repair team who will investigate the
fault, and arrange for a repair quote to be sent out.


The fact the source voltage could be adjusted suggests they could update
the EEPROM, but I'm puzzled why the ammeter adjustment could not be
completed. I'm not sure if they have updated the source voltage at this
point. Every voltage is low, but all are in spec. I'd hope they would be
able to increase the output voltage a little there.

For what it is worth, here's the cal certificate of one I sent in a month
or so ago.

http://www.kirkbymicrowave.co.uk/tmp/1-9690444179-1-combined-file.pdf

I was told that one needs a new CPU. I might have some more information
tomorrow, as Keysight (UK) are contacting the USA for support.

Dave
___
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

Re: [volt-nuts] Two 4338B high resistance meters fail on the same range - Keysight can't adjust EEPROM of either.

[Dr. David Kirkby]

On 2 May 2018 at 14:25,  wrote:

> "This reflects my experience when using
> it to measure close tolerance resistors - measuring them at low voltages
> gives poor results, but at higher voltage, the resistances are measured
> more accurately."
>
> I noticed similar results in general, over years ad several instruments.
> Always wondered why, but we have a rule-of-thumb: if the part is to be
> used at X KiloVolts, test it at X Kilovlolt.
>

I am sure your advice is good, but I based measurements on the best
resistors I could find at sensible prices from Farnell.

The issue on the 4339B is the accuracy of the internal 0-1 kV voltage
source, if set to low voltages. I don't have the time at the moment to hunt
for the exact specifications, but the calibration certificate  give the
output voltages the meter is set to, and the voltage limits. I calculated
them as a percentage.

0 V -> +/- 0.1 V (infinite percentage)
10 V -> +/- 0.12 V (+/- 1.2%)
25 V  -> +/-  0.14 V (+/- 0.56%)
50 V -> +/- 0.18 V (0.36%)
100 V -> +/- 0.26 V (+/- 0.26%)
...(I will miss out 200 V, 201 V, 250 V for safe of brevity)
500 V -> +/- 1.3 V (+/- 0.26%)
1000 V -> +/- 2.1 V  ( +/- 0.21%)

The basic uncertainty of the instrument is 0.6%, but clearly if the output
voltage is set to a low value, the percentage error in the voltage is high,
so the percentage error in the resistance will be high. The above would
suggest using a voltage under 50 V is going to compromise accuracy and
using 100 V or more is better.

The uncertainty of the ammeter also depends on the range it is on, and not
surprisingly that has a higher percentage error on its lowest range (100
pA) than on its highest range (100 uA).

The Agilent 4339B is said to work from 1e3 to 1.6e16 ohm. Clearly to
measure 1000 ohm, any voltage above 0.1 V would exceed the full scale of
the ammeter on its least sensitive range (100 uA). Setting the source
voltage at 0.1 V is likely to result in significant errors reading a 1000
ohm resistor. But clearly a "high resistance meter" is not designed to
measure 1000 ohm resistors. I expect a £5 handheld multimeter from China
would do a better job at measuring 1000 ohm than what this instrument
does.

Sorry, I don't know about the HP 4328A. Personally I would have no concerns
about breaking the seals on an instrument of that age. I would consider it
prudent to check for any leaking electrolytic capacitors or other nastiness
that may reside inside an old instrument.

Dave
___
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

Re: [volt-nuts] Two 4338B high resistance meters fail on the same range - Keysight can't adjust EEPROM of either.

[Dr. David Kirkby]

On 2 May 2018 at 10:37, David C. Partridge 
wrote:

> My bet is that they've lost the "secret sauce" for updating the EEPROM :(
> So it's measuring as best it can with no calibration adjustments stored.
>
> Dave
>

Dave,

Your comment got me to check something, which reveals something VERY
interesting, and is perhaps the source of the problem! I owe you a beer!

I initially assumed the calibration procedure required some software to
check the performance of the 4339B, and if out of specificaton update the
EEPROM. But upon reading the user and service manuals, I find that's NOT
the case.

The user manual describes how to check the performance, which requires no
software. The service manual describes how to adjust the instrument if the
performance is not right. The adjustment which needs software.

Furthermore, it seems to me the procedure used by Keysight to verify the
performance maybe wrong, although I am not going as far to say it is, as
maybe they are doing something that's not obvious from the calibration
certificate. Looking in the user manual, it would appear one is supposed to
verify the performance on the 10 nA range by setting the output voltage of
the 4339B to 1 V, measure the voltage on a 3458A, set a resistance box to
10^8 ohms and calculate the current, which should not be assumed to be 10
nA unless the 3458A indicated 1. V, I have not checked the
specification of the 4339B when generating 1 V, but when set to 0 V, it
should output 0 +/- 0.1 V and when set to 10 V it should output 10 +/- 0.12
V. So at low voltages, this is not an accurate voltage source. At higher
voltages it is a lot more accurate. This reflects my experience when using
it to measure close tolerance resistors - measuring them at low voltages
gives poor results, but at higher voltage, the resistances are measured
more accurately.

I am wondering if Keysight are assuming the 10 nA is generated when the
output voltage is set to 1.0 V.

If out of specification, the EEPROM should be updated with software. I'm
assuming that software is written to compute current based on what voltage
the 3458A measures, rather than what voltage the 4339B is set to output.

To answer Illya's questions, the EEPROM is a Xicor X28C64P-20. I can't find
any reputable supplier with those - plenty on eBay, but I am always
concerned about counterfeits on there. Someone suggested a Mouser P/N.
AT28C64B-15PU would probably do, but I decided to buy the EEPROM directly
from Keysight (P/N 1818-4808). I'm glad I did, as it is removed any doubt
about the suitability of the EEPROM. I'm sure if I had bought the EEPROM
from Mouser or eBay, Keysight would have suspected an incompatibility of
the EEPROM.

This has certainty got me thinking about what might be happening, although
the fact Keysight have said they can't update the EEPROM, suggests they
have the software to do it.

Dave
___
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

[volt-nuts] Two 4338B high resistance meters fail on the same range - Keysight can't adjust EEPROM of either.

[Dr. David Kirkby]

I"m pulling my hair out over an identical problem on two instruments. I am
hoping someone might think of a possible cause I have not thought of. Sorry
the post is a bit long, but this is not any easy problem to describe.

I have an Agilent 4339B high resistance meter. This instrument essentially
consists of a variable power supply (0.1 V to 1000 V) and a very sensitive
ammeter. It works out resistance using Ohms Law. It can display resistance,
current, surface resistively and volume resistively.

The service manual states there are no adjustable components in this - all
calibration is performed using software that updates an EEPROM. The EEPROM
is on the CPU board.

This was sent to Keysight in the UK for a firmware upgrade and calibration.
They updated the firmware (stored in a ROM), but the 4339B failed
calibration.

* All the output voltages from the internal PSU were within specification.

* The 10nA current range was slightly out of specification. It was reading
about 0.8℅ high, but the specification is about +/- 0.6%, so it was only
slightly out of specification. (All other ranges were within specification,
but some were not far from the limits. One range might have been 0.5% off)

I think the full scale of the current ranges are 10 pA to 100 uA, so 10 nA
is not at either extreme.

* All resistance measurements were within specification. (Keysight test up
to 1e11 ohms,   but it can read up to 1.6e16 ohms. I guess they simply
can't get accurate resistors above 1e11 ohms).

Calibration at Keysight includes any firmware upgrades if you request
updates.  It also includes the cost of any adjustments needed - unlike most
calibration labs.

Keysight said the EEPROM could not be adjusted to bring the 10 nA range
within specification, so it needed a new CPU board. I never received a
formal quote for repair, but I was told about £2000 (GBP), which seemed a
lot considering the CPU board is about $600 (USD) from Keysight.

These meters sell for around $3000, but other instruments available for far
less use the same CPU.  I was intending repairing my 4339B  by swapping CPU
boards from a cheaper instrument, and using a new  EEPROM, just in case it
was the EEPROM faulty, as that goes in a socket on the CPU board.

However, I  managed to find another 4339B at a good price, so that was
purchased and plans to repair the first instrument were put on hold.


I asked for a quote for calibration based on it having a blank EEPROM. I
thought this would be advantageous, as Keysight could put each range "spot
on". I expected the cost to be a bit higher but it was not.

Much to my surprise, the instrument worked and seemed reasonably accurate
even with the blank EEPROM.

I sent this second 4338B to Keysight for calibration. A couple of days
later i received an email from Keysight telling me the second  instrument
has a fault. The fault is on the 10 nA range (as the first instrument) and
the EEPROM can't be adjusted (like the first instrument). This time it is
reading about 0.7% low, which is not much out considering the specification
is about +/- 0.6%.

So I now have two 4339Bs, both being within specification on all ranges
except 10 nA, and neither being adjustable! So naturally I queried why both
instruments appear to have the same fault.

I then received an email from someone st Keysight who had noticed I said
the EEPROM was blank. He asked where did I get the EEPROM from. LUCKILY I
had bought the EEPROM directly from Keysight,  despite I could have got s
very similar one from Mouser for a tenth of the price or a supposedly
identical one for even less from China on eBay.

I am hoping to speak to someone at Keysight  tomorrow,,  but does anyone
have any ideas what could cause two instruments to be slightly out of
specification on the same range, but neither instrument will allow them to
update the EEPROM?

Note one instrument reads high and the other low. I can understand that
perhaps the resistors used in the current to voltage converter on the 10 nA
range might be a bit less stable than used on other ranges, but I can't
understand why Keysight can't bring the meters in spec just by updating the
EEPROM.



Dave
___
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

Re: [volt-nuts] Cropico DO4A Digital Ohmmeter

[Dr. David Kirkby]

On 30 April 2018 at 10:45, Nigel Clarke via volt-nuts <volt-nuts@febo.com>
wrote:

> -Original Message-
>
> From: Dr. David Kirkby <drkir...@kirkbymicrowave.co.uk>
> To: gandalfg8 <gandal...@aol.com>; Discussion of precise voltage
> measurement <volt-nuts@febo.com>
> Sent: Sun, 29 Apr 2018 22:18
> Subject: Re: [volt-nuts] Cropico DO4A Digital Ohmmeter
>
> I see this is a low-resistance (10 u ohm resolution) ohmmeter. Have you any
> idea how you are going to check the calibration? I just bought a Simpson
> 444, which has 1 u ohm resolution. I have not got it yet, but are wondering
> how I am going to check the calibration.
>
> 0.005% resistors are available from Farnell in a fairly limited number of
> values, but certainty not in the range of values needed for a milli/micro
> ohm meter.
>
> Dave
>
> -
>
> Whoops, whilst checking the calibration is one thing, actual self
> calibration on the DO4A is perhaps not looking quite so straightforward,
> it's an automated calibration process that requires six set resistor values
> of 4mohm, 40 mohm, etc up to 4Kohm, and a quick check online doesn't show
> high tolerance versions of these values exactly falling out of the woodwork!
>
> Nigel, GM8PZR
>

They are annoying values! Often one see 100 u ohm, 1 m ohm, 10 m ohm, but
most I have seen have resistances starting with the number 1.

The Simpson 444 I bought can only read up to a maximum of 2 ohms, which is
a bit limiting it must be said. The lack of GPIB, (or any other computer
interface), is another major inconvenience too.

I feel the low resistance meters that I have seen, all have some annoying
limitations. I've contemplated whether it is possible to make something
better, which outputs 0-10 V to be read by a normal multi-meter. Issues
seem to be

* Some are AC only, which makes them useless for inductive components.
* Some are DC only, which makes them suspeptable to thermal EMF
* Some use high currents, which can damage sensitive components
* Some can use fairly high voltages, which can break down oxides. (The
Simpson 444 does not output more than 100 uV, which seems quite unique in
this way)
* Some don't have GPIB
* Some like my Simpson 444, has a very limited maximum resistance - in this
case just 2 ohms.
* The Keysight 34420A has an impressive 100 n ohm resolution, but achieves
this by having a 1 ohm range with a 7.5 digit meter.

A combination of issues leaves me wondering if something better could not
be designed. But the only sensible way I can see would be an add-on for a
normal bench multimeter.

Calibration seems a non-trivual task, even for a commerical unit like
yours, so would be quite tricky for a home-brew unit, unless one spent a
fortune on calibration standards.

Dave
___
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

Re: [volt-nuts] Cropico DO4A Digital Ohmmeter

[Dr. David Kirkby]

On 29 April 2018 at 21:57, Nigel Clarke via volt-nuts 
wrote:

>
> Sorry, I realise now I could have explained better, I do know what
> transistor it is but that's not the problem, this looks to be quite a
> complex power suply/charger circuit, with at least three unmarked
> adjustment pots so if I change the device, even for the same part number,
> it's quite possible it will need readjustment and that's what I don't have
> any information on.
>
> Nigel, GM8PZR
>


I see this is a low-resistance (10 u ohm resolution) ohmmeter. Have you any
idea how you are going to check the calibration? I just bought a Simpson
444, which has 1 u ohm resolution. I have not got it yet, but are wondering
how I am going to check the calibration.

0.005% resistors are available from Farnell in a fairly limited number of
values, but certainty not in the range of values needed for a milli/micro
ohm meter.

Dave
___
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

Re: [volt-nuts] Would you be concerned if the manufacturer does not have an uncertainty budget, so can't provide uncertainties in a calibration?

[Dr. David Kirkby]

On 21 April 2018 at 09:32, Florian Teply <use...@teply.info> wrote:

> Am Fri, 20 Apr 2018 14:37:22 +0100
> schrieb "Dr. David Kirkby" <drkir...@kirkbymicrowave.co.uk>:
>
> > The columns below, from left to right are
> >
> > Device type (whether the DUT is floating, or grounded one side).
> > Resistor setting (ohms)
> > Votage (V)
> > Measurement time (Long or Short)
> > Test limits (+/- ohm)
> > Test results (ohm)
> >
> > FLOAT 1E6 100 SHORT +/- 0.0086E6 -.0019E6
> > FLOAT 1E7 100 LONG +/- 0.0063E7 -.0016E7
> > FLOAT 1E8 100 LONG +/- 0.0073E8 -.0027E8
> > FLOAT 1E9 100 LONG +/- 0.0093E9 -.0032E9
> > FLOAT 1E10 100 LONG +/- 0.0273E10 +.0095E10
> > FLOAT 1E11 100 LONG +/- 0.0453E11 +.0080E11
> > FLOAT 1E11 100 SHORT +/- 0.0550E11 +.0086E11
> > FLOAT 1E11 10 LONG +/- 0.0546E11 +.0113E11
> > GROUND 1E7 100 LONG +/- 0.0065E7 -.0017E7
> > GROUND 1E11 10 LONG +/- 0.0573E11 +.0107E11
> >
> > That strikes me that the assumption is the values are what their
> > nominal values are, but I wonder how accurate they are.
> >
> I might be wrong, but to me it seems like the resistors are not
> exactly nominal but slightly off. But the uncertainty of the
> measurements is larger than the deviation. Or were you referring to the
> notion that the uncertainties are symmetrically distributed? I'd be
> pretty surprised if the uncertainties were asymmetrical for that
> matter.
>
> Best regards,
> Florian
>


Florian,

how do you determine that the resistors are not assumed to be the nominal
value?

As far as I can see, taking the example of a 1e11 ohm resistor grounded at
one end (very last entry on table), the meter should read 1e11 +/-
0.0573e11 ohms. My meter read 0.010e11 ohms high, so was in spec, as
0.010e11 is less than 0.0573e11. As far as I can determine, the fact the
permissable range of the meter is +/-x, rather than +x, -y, means the
nominal values are assumed.

I put the complete cal certificate here.

http://www.kirkbymicrowave.co.uk/tmp/1-9690444179-1-combined-file.pdf

What I also find a bit odd, is the 16340A RC box used for calibrating the
meter, is itself not due for calibration for over a year.

I am awaiting a call/email from the calibration manager at Keysight (UK),
and I've been advised Keysight (UK) have contacted Keysight in the USA to
see what they can provide, as a calibration *with* uncertainties is listed
on the Keysight (USA) website.

I have no formal requirement for needing the uncertainties, but I am a bit
worried the fact that Keysight (UK) seem to use a resistance box that is
calibrated less than once/year, and can't provide the uncertainties, and as
far as I can tell (although you disagree), it would appear the nominal
value of the resistors are used. . It does not exactly inspire a lot of
confidence.

Dave
___
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

Re: [volt-nuts] Would you be concerned if the manufacturer does not have an uncertainty budget, so can't provide uncertainties in a calibration?

[Dr. David Kirkby]

On 19 April 2018 at 16:42, <acb...@gmx.de> wrote:

> -a calibration certificate without uncertainsties is totally useless. in
> is not even a calibration.
> -I have never understood why people are so keen on getting things
> calibrated at Keysight.
>

I must admit I do have some concerns, about this. There are 3 aspects to
the calibration

1) Calibrate the voltage of the internal source using a 3458A. I have no
concerns a 3458A is not more than capable of measuring the voltage.

2) Measure the resistors in the 16340A. What puzzles me here, is that when
I had another 4339B calibrated, the limits on measuring those resistors
were symmetrical about the nominal values of 1e6, 1e7, 1e8, 1e8, 1e10 and
1e11 ohms. I would have expected the limits to be asymmetrical, because
those resistors are probably not their nominal value.

The columns below, from left to right are

Device type (whether the DUT is floating, or grounded one side).
Resistor setting (ohms)
Votage (V)
Measurement time (Long or Short)
Test limits (+/- ohm)
Test results (ohm)

FLOAT 1E6 100 SHORT +/- 0.0086E6 -.0019E6
FLOAT 1E7 100 LONG +/- 0.0063E7 -.0016E7
FLOAT 1E8 100 LONG +/- 0.0073E8 -.0027E8
FLOAT 1E9 100 LONG +/- 0.0093E9 -.0032E9
FLOAT 1E10 100 LONG +/- 0.0273E10 +.0095E10
FLOAT 1E11 100 LONG +/- 0.0453E11 +.0080E11
FLOAT 1E11 100 SHORT +/- 0.0550E11 +.0086E11
FLOAT 1E11 10 LONG +/- 0.0546E11 +.0113E11
GROUND 1E7 100 LONG +/- 0.0065E7 -.0017E7
GROUND 1E11 10 LONG +/- 0.0573E11 +.0107E11

That strikes me that the assumption is the values are what their nominal
values are, but I wonder how accurate they are.

3) Apply known currents, again using the test box.

I've asked Keysight if they are certain that the meter can be put within
specification, and if not whether it might be sent outside the UK to be
calibrated.

To be honest, I don't really NEED the uncertainties, but the fact they
can't provide them does concern me a bit.

Dr David Kirkby Ph.D C.Eng MIET
Kirkby Microwave Ltd
Registered office: Stokes Hall Lodge, Burnham Rd, Althorne, CHELMSFORD,
Essex, CM3 6DT, United Kingdom.
Registered in England and Wales as company number 08914892
http://www.kirkbymicrowave.co.uk/
Tel 01621-680100 / +44 1621-680100
___
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

Re: [volt-nuts] Would you be concerned if the manufacturer does not have an uncertainty budget, so can't provide uncertainties in a calibration?

[Dr. David Kirkby]

On 19 April 2018 at 16:42,  wrote:

> -a calibration certificate without uncertainsties is totally useless. in
> is not even a calibration.
>

Having bought the meter, it is not so useless if it tells me it is working
or not, but I do have some concerns I must admit.


> -I have never understood why people are so keen on getting things
> calibrated at Keysight.
>

Well, quite simply there's nobody else I would trust to calibrate much of
the Agilent equipment. I did contact one UKAS acredited lab, who quoted to
calibrate loads of bits of my equipment, but declined this meter. But when
I checked the companies uncertainties, I was totally unimpressed. For
example, their uncertainty on capacitance at 1 MHz was well in excess of
0.05%, yet they quoted to calibrate the meter, which has a basic
uncertainty of 0.05%. I also found their prices were much higher than
Keysight.

Most companies are not going to be able to adjust Agilent stuff if it is
out of spec anyway, as often the software to make the adjustments is not
available. So I'm not convinced there is any half-sensible alternative.

Dave
___
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

[volt-nuts] Would you be concerned if the manufacturer does not have an uncertainty budget, so can't provide uncertainties in a calibration?

[Dr. David Kirkby]

I have an HP 4339B high resistance meter. It can read up to 1.6 x 10^16
ohms, with a basic uncertainty of 0.6%. It has a built in voltage source of
up to 1 kV.

I've contacted Keysight (UK) and asked for calibration cost, with
uncertainties, for this 4339B. However, they have said they can't provide a
calibration with uncertainties, and when I asked why, they have said they
do not have an uncertainty budget available that suites that model. Looking
at the Keysight website, a calibration with uncertainties is available in
the USA, but I guess for whatever reason Keysight UK don't have this
ability on this specific instrument. On other instruments I have sent them,
I have never had this issue.

I expect if I really wanted to, I could get it shipped to the USA and
calibrated there, but I can't justify the costs that would be incurred if
it was shipped to the USA and back.

>From a practical perspective, I don't really need the uncertainties - it
was more for interest sake. I also have a reasonable degree of confidence
that as a reputable company, Keysight would not calibrate an instrument
unless they were confident they could determine if it is in or out of
specification.

The 4339B is a pretty obscure unit, requiring resistors up to 10^11 ohms to
calibrate it.

I'm sending this to Keysight with a blank EEPROM, so there will be no
calibration data whatsoever in the instrument. Hopefully that means
everything will be set right, and so likely to stay in specification longer
than it might otherwise do so. There are no trimmers in the 4339B - all
calibration is via the EEPROM. A 3458A is used for calibration of the
voltage source. I'm confidence the voltages will be measured accurately
enough, but a bit less confident about the values of the resistors used for
calibration.

Dave

Dr David Kirkby Ph.D C.Eng MIET
Kirkby Microwave Ltd
Registered office: Stokes Hall Lodge, Burnham Rd, Althorne, CHELMSFORD,
Essex, CM3 6DT, United Kingdom.
Registered in England and Wales as company number 08914892
http://www.kirkbymicrowave.co.uk/
Tel 01621-680100 / +44 1621-680100
___
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

[volt-nuts] Does desoldering and resoldering an LTZ1000A reset the ageing?

[Dr. David Kirkby]

There seems to be plenty of evidence that meters like the 3458A improve
stability over time. I believe that most/all is due to improved stability
of the LTZ1000A.

Does anyone know if desoldering one and resoldering resets the aging
process? I see a number of used LTZ1000A ICs on eBay that look like they
have been poorly removed. They are about the same price as a new LTZ1000A.
I wonder if
___
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

[volt-nuts] Does desoldering and resoldering an LTZ1000A reset the ageing?

[Dr. David Kirkby]

There seems to be plenty of evidence that meters like the 3458A improve
stability over time. I believe that most/all is due to improved stability
of the LTZ1000A.

Does anyone know if desoldering one and resoldering resets the aging
process? I see a number of used LTZ1000A ICs on eBay from China that look
like they have been poorly removed. They are about the same price as a
brand new LTZ1000A.

I wondering if properly removed, a used chip is no more stable than a new
one.



Dave
___
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

Re: [volt-nuts] Open day at the National Physical Laboratory (NPL) on Thursday 17 May 2018.

[Dr. David Kirkby]

On 3 Apr 2018 22:12, "Jeremy Nichols"  wrote:
>
> Man, that would be wonderful! Pity the flight from California to the U.K.
> is considerable more than £3!
>
> Jeremy
> N6WFO

Yes, its a shame that the plane ticket is not cheap.  Perhaps you could
consider a holiday to the UK to coincide with the following NPL open day
which I suspect will be in 2020.

I only have access to my mobile phone at the minute,  which I don't find as
good as a PC for searching the web. However,  a brief search would indicate
NIST do not have an open day.

Perhaps people in the US could contact NIST to see if NUST would consider
doing the same as NPL, and making NIST open for a day, every year or two.
Attach a copy of the visitor guide for NPL, to show what the UK does. That
guide should be available shortly,  but last I looked only the 2016 guide
was online.

I don't know if other national labs like METAS do the same as NPL.

NPL open up all the labs related to the 7 SI units. The area open to the
public on timekeeping is much more impressive than the area about the volt.
But not every lab is open.

I suspect that if you have a particular interest in a topic and contact the
right person at NIST,  they are quite likely to be more than happy to show
you around their area. I am hoping to arrange to visit a couple of areas at
NPL I doubt will be open to the public, due to their very obscure nature.

Dave
___
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

[volt-nuts] Open day at the National Physical Laboratory (NPL) on Thursday 17 May 2018.

[Dr. David Kirkby]

NPL opens their doors to the public once every 2 years. It is well worth
going. Tickets are only 3.00 each, and that money is donated to a cancer
charity. More details at

http://www.npl.co.uk/open-house/

To make the most of it, you need to

1) Arrive early (14:00)
2) Leave when they close (20:00)
3) Walk around the many labs. Even 6 hours is not enough time to visit
everything.

I think you need to be reasonably fit, since it is not a place where you
sit down in a chair and listen to lectures all day.

I think NPL do a really good job, as they manage to put on something that
is interesting to both children and professional scientists. Lots of
schools have trips there for the day.

Dave
___
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

Re: [volt-nuts] How can I make a 2000 V DC meter with an input resistance of at least 100 T ohms?

[Dr. David Kirkby]

On 24 March 2018 at 17:34, Jeremy Nichols  wrote:

> I made a high-value resistor using motor oil and a couple of stainless
> bolts. It worked for what I was doing (testing an HP-425A
> Microvolt-Ammeter) but calculated as only 8,500 Megohms.
>
> Jeremy
>

I had some discussions some time ago about using oil as a dielectric in a
capacitor with someone at NPL. He said the loss of both cyclohexane and
Polydimethylsiloxane (PDMS = silicon oil) is very low. He said the only way
I would measure the loss of them was a resonate method, and detecting small
changes in Q. My thoughts on putting them as the dielectric in a capacitor
and measuring on an LCR meter would not work, nor would my transmission
line. I had already satisfied myself that using a coaxial probe and VNA
would not work.

As he said, cyclohexane is nasty stuff, but PDMS is much more
environmentally friendly.



Dave
___
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

Re: [volt-nuts] Help needed identifying triaxial connector on HP 4339B high resistance meter - measures to 1.6 x 10^16 ohms.

[Dr. David Kirkby]

On 23 March 2018 at 15:27, Jerry Hancock  wrote:

> what others do is just buy the available Trompeter triax connector and
> file-off the host connector pins.  I went through all the trouble to get
> the right connectors and then looked at my Electrometer and saw someone had
> already filed off the extra pins leaving one.  I was a upset on many levels
> as I would never file off anything on a piece of test equipment, except may
> the RIGOL label.
>
> look for an eBay seller n2cbu.  Great guy, sent me extra connectors and
> cable.  The biggest challenge in making your own cables is the fit between
> the connector and cable.  There are about a dozen types of triax connectors
> for the same number of cables.
>
> Regards,
>
> Jerry
>

Thank you Jerry,

The idea of destroying an instrument to make the socket fit a plug is one I
would not do!

Worst case, on a cheap and nasty bit of kit, I might consider changing the
socket for triaxial BNC, but I have no desire whatsoever to do that on the
4339B, which sell for several thousands of dollars. I have already sent the
meter once to Keysight for calibration, which they can obviously do if it
has the right connector on it. If one started changing the connectors, then
it would never get calibrated again. Depending on the age/value/rarity of
the connector, I might consider other options, but not this time.

On Monday I should have a partially complete Agilent 16339A component test
fixture

https://www.ebay.co.uk/itm/Agilent-16339A-Component-Test-Fixture/112871963210

arrive. (It cost me $400, which is more than the $350 I paid for the
meter). That fixture will have the correct plug on it. HOPEFULLY there will
be a manufacturer and part number on the plug. Also, I will have the
ability to take a decent photo, so hopefully someone experienced has more
chance of being able to positively identify the connector. I might try
asking Keysight again. They told me the interlock connector was a Hirose,
and knowing that I managed to work out a plug that fits.

I've bought a couple of 4349Bs, which are quad channel high-resistance
meters that take the same CPU as my 4339B. I'm hoping to do a bit of
transplant surgery and hopefully get my 4339B to the point it can be
calibrated properly - Keysight were unable to adjust it before as the CPU
board apparently has a fault which is stopping the EEPROM being updated.

When sent back to Keysight, it will have a 'heat transplant' of a CPU, and
a new EEPROM, so all calibration data will be missing, as that's stored in
the EEPROM. I'm pleased to say Keysight are not going to charge any extra
to calibrate the meter with a blank EEPROM. So hopefully I will get this
meter right.

Dave
___
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

Re: [volt-nuts] How can I make a 2000 V DC meter with an input resistance of at least 100 T ohms?

[Dr. David Kirkby]

On 23 March 2018 at 01:49, kc9ieq via volt-nuts  wrote:

> How about using (or building) an additional 2kV power supply and a
> sensitive meter movement like a differential voltmeter, adjusting
> for/measuring the null?  Impedance at null will be theoretically infinate,
> current will be theoretically zero, and you can measure/monitor the voltage
> of your second supply directly with the probe/meter of your choice.
> Regards,Chris
>

No, that will not work for me, as while the impedance at null is infinite,
it is not when not nulled, and that will mess up the measurements.

Absolute accuracy is not important. +/- 10% or even 20% would be okay. I
want to measure a couple of voltages and compare them. As long as the meter
reads the same with identical input voltages, that is fine.

Dave
___
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

Re: [volt-nuts] How can I make a 2000 V DC meter with an input resistance of at least 100 T ohms?

[Dr. David Kirkby]

On 23 March 2018 at 01:07, Bob Albert via volt-nuts 
wrote:

>  I found several electrostatic voltmeters on ebay.  The brand I remember
> is Sensitive Research.
> Bob
>

So something like this?

https://www.ebay.com/itm/Singer-ESD-7-Sensitive-Research-Electrostatic-Voltmeter-1500-Volt-Range/122976453378

1500 V would probably do. I must admit, I don't understand how these work.
Do you need to have a power supply to balance the voltage? I can't see how
taking almost no current can physically make a meter needle move, as that
needs energy.

I see some are contact, and some non-contact.

It is 01:45 here, so I am just about to go asleep, but will read any
replies later today.

I would be interested in making a more modern version, but really don't
know how.

Dave
___
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

[volt-nuts] How can I make a 2000 V DC meter with an input resistance of at least 100 T ohms?

[Dr. David Kirkby]

I want to measure a high voltage, but put minimal load on the circuit.
Looking at the Keithley electrometers, the input resistance is at least 200
T ohms, but they tend to have a maximum of 200 V FSD.

A 2000 V source, and a 200 T ohm resistor gives a current of 10 pA, which
itself is easy to measure. But one can't buy 200 T ohm resistors. I looked
at RS in the UK, and the highest value resistor I could find is 1 T ohm,
and they are £163 each (around $200).

Maybe fabricating ones own resistor is possible, but I suspect there's a
better way. Keithely manage to keep a 200  T ohm resistance on the 200 mV
range, and there's no way that can be measured with an ammeter, which would
require an ammeter with a full scale deflection of 1 fA, which is much
smaller than the 2 pA FSD on its most sensitive range.

Any thoughts?

Dr David Kirkby Ph.D C.Eng MIET
Kirkby Microwave Ltd
Registered office: Stokes Hall Lodge, Burnham Rd, Althorne, CHELMSFORD,
Essex, CM3 6DT, United Kingdom.
Registered in England and Wales as company number 08914892
http://www.kirkbymicrowave.co.uk/
Tel 01621-680100 / +44 1621-680100
___
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

Re: [volt-nuts] Bohnenberger electrometer

[Dr. David Kirkby]

On 6 March 2018 at 09:40, Dr. David Kirkby <drkir...@kirkbymicrowave.co.uk>
wrote:

> Sorry this is not precision voltage measurement, but it is not unrelated.
>
> As a radio club project, we are building a simple electroscope, with no
> active components. The gold leave variety would work, but two bits of
> alluminum foil do too.
>
> My plan was to go one better, and build a Bohnenberger electrometer.
>

For what it is worth, this is my design:

http://www.kirkbymicrowave.co.uk/tmp/G8WRBs-electrometer.jpg

There's 600 V DC between two strips of PCB material. A 600 V 47 uF
capacitor was charged to 600 V. A small bit of aluminum foil, between the
plates, then moves to the left or right, depending on whether the charge is
positive or negative. The big capacitor, which is 2.2 nF 15 kV is not doing
much apart from being a structure to hold other parts. It has large lugs on
it, where multiple M6 screws can be fitted, so it is nice electrical
insulator. Its actual capacitance (2.2 nF) is insignificant when in
parallel with 47 uF.

Under sufficient applied field, and with sufficient charge, it is possible
to get the foil to oscillate from side to side like a pendulum. I believe
what happens is if a negative charge is applied to the foil, it gets
attracted to the positive plate, which causes them to touch, so the foil
receives a positive charge - the opposite of what it had before. This
causes it to move in the other direction. It is possible to get it to
oscillate back and forth. I expect, with a sufficient mass and very high
electric field, a pendulum could be made to make a clock, but with a little
bit of tin foil, the foil would clearly break quite quickly. A more
substantial structure would be required, which I suspect would need some
very high voltages.

A Google of 'electrostatic clocks' does indicate they exist, although I
have not looked into how they work. But I believe a sufficiently high
electric field could make a pendulum swing, and that of course could make a
clock.

Anyway, it was interesting playing with this.

I am wondering if there's any way to detect the polarity of a charge,
without having any power source. Clearly the gold leaf electroscope can
detect charge, but does not need a power supply. The Bohnenberger
electrometer can detect polarity too, but needs a power supply. I was
wondering if the charge could be applied to two diodes, which were each
connected to a plate. The it may be possible to charge one plate only, as
only one diode would conduct, so only one plate would be charged. The the
leaf would be repelled from whatever plate has the same charge.

Dave
___
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

Re: [volt-nuts] Bohnenberger electrometer DANGER

[Dr. David Kirkby]

On 8 March 2018 at 07:19, Andre  wrote:

> Hi, re. capacitors it might be worth mentioning that the normal equation
> assumes charge and discharge through a constant current.
>

What 'normal equation' do you mean?


> Don't forget that the equation includes a non linear term so you'll need
> to take that into account (Q=CV2 iirc) where Q is Coulombs, C is
> capacitance.
>

I am puzzled by CV2.  The energy (joules) stored in a capacitor is 1/2 C
V^2, where C is the capacitance and V the voltage. I don't know if that's
what you mean.


> If this is done using something like an LM317T in CC mode or even a string
> of them (my idea) with anti-overload circuitry added externally then this
> may well work.
> Any series resistance will cause problems so you'd need quite a lot of
> regulators but there are ways to use JFETs selected by hand if you really
> wanted to
> make a test setup.
>

I am totally lost here!

If anyone has an explanation of whether any of the energy to move the leaf
comes from the battery/capacitor, or does it all come from the charge
applied to the unit, I would like to know.  If no energy (apart from
leakage) comes from the device applying the electric field, a small
capacitor is suitable, and very safe. If at least some of the energy
required to move the leaf comes from the voltage supplying the electric
field, then a small value capacitor will be no use.

This is a fairly low priority task for me at the minute, as I need to do
some real work until Friday evening. But over the weekend I will play with
this.

Dave
___
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

Re: [volt-nuts] Bohnenberger electrometer DANGER

[Dr. David Kirkby]

On 7 March 2018 at 06:29, Andre  wrote:

> Please be VERY VERY careful. To be honest its far safer to use CCFL
> drivers and rectify them with camera diodes in series and the absolute
> minimum capacitance for the job, shunted with a high value resistor.
>

The problem with 2.2 nF is it is difficult to know what voltage is on the
capacitor at any time, since with a 10 M ohm multimeter, the time constant
is 22 ms. I have a high voltage probe around somewhere, which probably has
a 100 M ohm input impedance, but that would still only give a time constant
of 220 ms, which is too short to measure easily.

I have 47 uF @ 650 V (or it might have been 550 V) capacitor on order, but
I might go to something a bit lower capacitance if the charge storage is
not required.

I would like to know where the energy comes from to move the leaf. I wonder
if any is taken from the capacitor. In the gold leaf electrometer, with no
internal supply, it is clear the energy much come from the charge on the
plates. But when there's an electric field, that might not be the case. I
was thinking of sticking a 50 uA FSD meter inside, to see if any current is
take from the capacitor, but I don't know if 50 uA would be sufficiently
sensitive to deflect.

Clearly having an electrometer here would be useful for these sorts of
experiments, but I don't have one. I see a reference on here recently to
the Keithley 642 being one of the best, but whilst the basic meters are not
that expensive, the test head and cable are much rarer, so attract a much
higher price.

In any case, there's not a single half-decent electrometer on eBay in the
UK at the minute, and I need it before Monday.


> I have a few inverters , 10M resistor packs and diode strips here if
> anyone has a use on the understanding they are only to be used at your own
> risk, and for the intended purpose.
>
> Microwave capacitors can be deadly (you could DIE!) under the wrong
> circumstances, fibrillation can occur even with quite small shocks down to
> <8J if you get hit badly or have an undetected problem. I don't want to
> scare people but it is a serious risk.
>

It's fairly obvious to me, based on a few quick experiements last night,
that kV is not needed for this. Whilst I'm not doubting one could make an
electrometer (electroscope???) of greater sensitivity using a higher
electric field, this is good enough for a demonstration, and to learn a
bit. For quantitative measurements, I will look for a Keithley
electrometer, at a later date.


> -A
>


Dave
___
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

[volt-nuts] Bohnenberger electrometer

[Dr. David Kirkby]

Sorry this is not precision voltage measurement, but it is not unrelated.

As a radio club project, we are building a simple electroscope, with no
active components. The gold leave variety would work, but two bits of
alluminum foil do too.

My plan was to go one better, and build a Bohnenberger electrometer. Does
anyone here have experience of building a Bohnenberger electrometer, or
know much about them? They are similar to the gold-leaf electroscope, but
have one leaf sitting in an electric field. So the leaf moves one way or
the other, depending on the polarity of the charge. Or some other
electrometer, that does not use any active components - no ICs or
transistors.

I believe the original design was built with some sort of battery, but my
intention was to use a capacitor and charge it up. I'm not sure of what
sort of electric field / energy / stored charge is required though. I have
two obvious options for a voltage source based on what I can find at home.

1) 2 nF 15 kV capacitor which I can charge to about 4.2 kV easily (Q = 5.4
uC)
2) 2200 uF 400 V electrolytic capacitor which I can charge to 400 V (Q=0.8
C)

Clearly capacitor 2 stores a lot more charge, but for any given spacing of
plates, capacitor 1 creates am electric field 10 times higher than
capacitor 2.

Obviously if gold leaf or aluminum foil moves, that takes energy. Will that
come from the charge one puts on the top of the electroscope, or will some
come from the capacitor, so discharging the capacitor? If the latter,
capacitor 1 might discharge quite quickly due to its small capacitance,
whereas 2200 uF of capacitor 2 would not.

I do not wish the unit to be mains operated. I don't mind charging the
capacitor from the mains, but I want it to be standalone, independent of
any supply voltage.

Dave
___
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

Re: [volt-nuts] Precision high resistance measurements / calibration of HP 4339B high-resistance meter. Fix?

[Dr. David Kirkby]

On 2 March 2018 at 09:22, Andre  wrote:

> Maybe one bad resistor? I've read that tin whiskering can occur even on
> relatively recent equipment, slower than lead free but still a problem.
> I'd do a visual inspection just to see, shouldn't be an issue.
> -A
>

An issue with fingerprints would not totally surprise me. It is obvious the
seller had multiple meters, which were sent to a lab, which I am suspicious
of*. The seller said the lab would have swapped pieces between units to try
to get one working. He had at least 3.

1) My one, which has a recent(ish) Agilent serial number, and Agilent
written on the back, but an HP front panel.

2) Another which has HP on the back, but an Agilent front panel.

3) Another said to be working.

* I consider is lab suspicious, the fact mine was sold as having no output,
yet there was output, and it was within spec. It could be an intermittent
fault of course.

So its almost certain bits have been swapped between different units.

It is is finger prints, what would be the best way to remove them? I see
some say IPA, but others have said that can disolve solder resist.

I once had a Sun workstation which had one of the covers missing of the
back where sbus expansion cards

https://en.wikipedia.org/wiki/SBus

were supposed to be put. This was stored in the garage. Some mice decided
this Sun would make a nice home, and used it as a toilet! Needles to say
the board was covered in what mice excrete. After various attempts to get
it back to life, an hour or so in the bath with plain tap water did work.
But of course very low currents of the 4339B would prevent different
challenges to a digital board, where signals are either 0 or 1. But whilst
the 4339B may not be free of finger prints, it has not been used as a mouse
loo. So if it does require cleaning, it should be fairly modest, but I have
no idea what to use.

I buy a IPA on eBay for cleaning, which is claimed to be 99.9% pure, but I
doubt it is really that pure, so if IPA was used, I would buy from a proper
chemical supplier.

Dave
___
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

[volt-nuts] Precision high resistance measurements / calibration of HP 4339B high-resistance meter.

[Dr. David Kirkby]

I pickup up an HP/Agilent (front says HP, rear says Agilent) 4339B
high-resistance meter from eBay. The 4339B has an internal supply up to
1000 V, an ammeter to measure current, and obviously computes resistance
from Ohms Law. It is supposed to work up to 16 Peta ohms (1.6x10^16 ohms),
which would pass a current of 62.5 fA with 1000 V.

It was sold as non-working, with no output. Even attempting to get some
output was challenging as it had an obscure 6-pin interlock connector, and
there's no information in the manual about this. It also has a trixaxial
input connector with a screw thread. I asked Keysight for some information
about the connectors. I still don't know what the triaxial connector is,
but I have the interlock sussed - a HiroseHR10A-7P-6P(73) plug fits, and
there's some information about the wiring of this in the manual for the
11617C low-noise test leads.

Keysight offered to do a free technical evaluation, so I thought I'd take
them up on it, rather than waste too much time trying myself to get it
working. It was sent to Keysight and they sent me a report showing there is
output voltage, despite it being sold as having no output, and the output
is all in spec. Unfortunately, it was out of spec on one of the current
ranges. It is reading 0.082 nA low with a test current of 10 nA, but the
specification is +/- 0.063 nA. So it is only a little bit out, but it is
still out of spec. Test currents of 100 pA, 1 nA, 10 nA, 100 nA, 1 uA, 10
uA and 100 uA were used, so the 10 nA is neither at the low nor high end of
the range of the meter.

When I received an email copy of the free technical report, I assumed the
4339B had not been subjected to a full calibration as it was only tested
with resistors up to 10^11 ohms, but it is supposed to read resistance up
to 1.6 x 10^16 ohm, so the highest value resistor used during the technical
evualation is 5 orders of magnitude lower than the what the meter can read.
Also the meter was only tested at 100 V when reading resistors, whereas I
would have thought it more sensible to test at a higher voltage, given it
can output 1 kV.

I decided to pay Keysight for a full calibration, so I got a cal
certificate, which shows the out of spec reading.

http://www.kirkbymicrowave.co.uk/tmp/1-9690444179-1-combined-file.pdf

I was rather hoping the cal certificate would have some extra readings, but
I actually received no more technical information than Keysight had given
me for nothing, although they did update the firmware as I requested.

I have two questions.

1) Is 10^11 ohms a practical limit on making resistors that can be used for
calibration purposes? I don't know what the Keysight uncertainty on their
calibration standards are, so maybe 10^11 ohms is all its practical to
make.

2) Does anyone know if the meter can be adjusted on individual ranges? I
find it a bit hard to believe that given the ammeter was tested with
currents covering 6 orders of magnitude (100 pA to 100 uA), that there's no
adjustment on individual ranges. I doubt that it is possible to design a
circuit to cover that range, without switching in some different resistors
at some point.

But I'm told it can't be adjusted, and needs a new board.

I'm wondering if anyone knows anything about this meter, just in case
Keysight are wrong. I know they should not be, but it is not a current
instrument, so it's just possible the engineer did not know it could be
adjusted.

Dr David Kirkby Ph.D C.Eng MIET
Kirkby Microwave Ltd
Registered office: Stokes Hall Lodge, Burnham Rd, Althorne, Chelmsford,
Essex, CM3 6DT, United Kingdom
Registered in England and Wales as company number 08914892
http://www.kirkbymicrowave.co.uk/
Tel 01621'680100 / +44 1621-680100
___
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

Re: [volt-nuts] What's the probability of a random used 3458A passing a Keysight calibration?

[Dr. David Kirkby]

On 16 January 2018 at 17:33, Dr. Frank  wrote:

> I meant to say, that the ADC ASIC determines crucially the stability.. and
> this special serial number US28032500 is eventually affected by the AN-18
> service note. So that may be the reason, why they claim 2100$ for repair,
> i.e. replacement of A5, the ADC PCB.. and that had nothing to do with that
> ACV outlier. The "as left" data is not displayed, probably the instrument
> was completely adjusted afterwards. The cal report is also not online, pity.
>
> So I wouldn't touch that instrument at all, as the ADC drift problem
> (CAL?72) is not checked.
>
> Frank
>

I don't think it was adjusted, because if you look in the front, the
Keysight cal sticker says "Conditional cal".

My understanding is that a Keysight calibration will include any
adjustments needed, without extra payment.

See for example

https://literature.cdn.keysight.com/litweb/pdf/5990-6245EN.pdf

"Instrument adjustments included at no extra charge, when out-of tolerance
condition is found" That applies to any of the Keysight calibrations - even
the most basic non-accredited one.

I read AN-18, and see

Serial Numbers: US28031400 / US28032927

I assume that means it applicable to instruments with serial numbers in the
range US28031400 to US28032927, although it could have been a bit more
clearly written.

The application note mentions the A3 board, 03458-69503, not the A5 board.
Was A5 a typo, or is there something else?

If one see a used 3458A with a serial number in that range, is there a way
of determining if the board has been replaced or not?  I assume the part
number of board would tell you, but that may not be easy to see. Is there
any sequence of key presses that will determine if the board has been
replaced?
___
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

Re: [volt-nuts] What's the probability of a random used 3458A passing a Keysight calibration?

[Dr. David Kirkby]

But the seller told me he had been quoted 2100 Euros for repair, so I
assume Keysight thought it needs repair, not just adjustment. Also, as far
as I know, all Keysight calibration do include adjustments.

I'd like one, but don't really have the money, but I thought the price
excessive.

Dave

Dr David Kirkby Ph.D C.Eng MIET
Kirkby Microwave Ltd
Registered office: Stokes Hall Lodge, Burnham Rd, Chelmsford, Essex, CM3
6DT, United Kingdom
Registered in England and Wales as company number 08914892
http://www.kirkbymicrowave.co.uk/
Tel 01621'680100 / +44 1621-680100


On 16 January 2018 at 16:46, Dr. Frank <frank.stellm...@freenet.de> wrote:

> David,
>
> that instrument on ebay is definitely from the agilent area, i.e. built
> after 2000.
>
> It is really ok, and does not need any repair.
>
> Obviously, this AC range is a bit outside calibration @ 3V, 4MHz, but that
> is normal after some years w/o adjustment, and not a defect at all.
> Probably you know the different kinds of calibration at HPAK, obviously
> they chose the cal w/o adjustment option.
>
> Currently, the KS server is down, otherwise one could download the full
> calibration document, and check that, also the date of manufacturing .
>
> If you'd ever need these high frequency measurements, it's possible to do
> that by means of an appropriate signal generator and a thermocouple.
>
> The internal LTZ1000A circuit might stabilize with age, also the internal
> 40k VHP100 reference resistor might get better.
>
> The annual drift of the LTZ circuit is nominally 8ppm, but that is not
> fully specified.
> In theory, that applies only if the instrument is powered on continuosly.
> If it's switched off most of the time, the LTZ chip should not age at all,
> but it may show hysteresis (see AN-18, first item)
>
> So to my opinion, in this case it makes no difference, if you have an
> older or a younger instrument.
>
> The rest of the circuit is either (short term) stable, or not, also mostly
> independant from vintage.
> Due to the regular AutoCal process, this is of no real concern, as all
> these other drifts will be cancelled by the machine.
>
> The only component which determines the short term stability, is the ADC
> ASIC.
>
> It might have a good T.C., from zero to max. 0.5ppm/°C, and it might have
> a low timely drift in its calibration parameter CAL? 72.
>
> If latter is not the case, as described in AN-18, 2nd item, you really
> have a monetary problem.
>
> But in any case, this stability risk is the same for every vintage of
> instruments.
>
> Anyhow, I would prefer a newer unit like this one, as some other
> components degenerate over time, like the un-obtainium fast comparators.
>
> In the end, this instrument is not cheap, especially w/o proper
> adjustment. 3000$/€ would be a more reasonable price.
>
> Frank
>
>
> ___
> volt-nuts mailing list -- volt-nuts@febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/m
> ailman/listinfo/volt-nuts
> and follow the instructions there.
>
___
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

Re: [volt-nuts] What's the probability of a random used 3458A passing a Keysight calibration?

[Dr. David Kirkby]

On 16 January 2018 at 13:44, Dr. David Kirkby <
drkir...@kirkbymicrowave.co.uk> wrote:

> Maybe an Agilent meter might be a sweet spot - not as old as an HP, so but
> less stable than a newer Keysight.
>
> Dave
>

I meant to say, maybe an Agilent meter would not have the reliability
problems of an older HP, but be more stable than a new Keysight.

Does anyone know how old the units have to be to reach maximum stability?
Is it the LTZ1000A reference that improves with age, or the ADC? I assume
the zener reference, but I don't know.

Dave
___
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

Re: [volt-nuts] What's the probability of a random used 3458A passing a Keysight calibration?

[Dr. David Kirkby]

On 16 January 2018 at 05:01, John Phillips  wrote:

> my experience is that most of the eBay meters that do not give errors are
> very close to spec. These old meters do not drift as much as a new meter.
> If you have a good 10 volts and 10k resistor calibration is a snap...
> verifying cal in not as easy. The high-frequency AC cal is more difficult.
>

Clearly in the case of the eBay item, it was the high-frequency AC volts
that was out of spec. I would imagine a number of labs that may have good
enough DC and resistance standards, may well not have good enough high
frequency AC standards for this. So maybe that meter would pass at some
other labs, who have higher uncertainties than Keysight.

Anyway, not that I can afford a 3458A, but I added up the cost of the
meter, plus the repair cost, and found it was was not much below the cost
of a new meter. I can appreciate your point about a new meter drifting
more, but I can also imagine that some of the caps in those old meters
might start to show problems.  Maybe an Agilent meter might be a sweet spot
- not as old as an HP, so but less stable than a newer Keysight.

Dave
___
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

[volt-nuts] What's the probability of a random used 3458A passing a Keysight calibration?

[Dr. David Kirkby]

There's an "interesting" $5400 buy-it-now on eBay at the minute. It's
described as "Agilent 3458A 8.5 digit Multimeter CALIBRATED".

http://www.ebay.co.uk/itm/Agilent-3458A-8-5-Digit-Multimeter-CALIBRATED/
232593692038

When one reads the description, one can see it is an HP (not Agilent) 3458A,
that was sent to Keysight for calibration, but *failed* on the 3 V 4 MHz AC
voltage. Apparently it passed on everything else. Personally I would sell
that as "spares or repair" rather than "used" and "CALIBRATED", but
different people have different ideas of what is good or not.

Out of interest, I asked the seller what Keysight had quoted to repair
this. He said 2100 Euros, (which about $2600 USD or £1900 GBP). So to get
it in shape, it is not exactly peanuts.

The seller said to me that he has a *lot* of experience of 3458As, and
knows that a used one has less than a 50% chance of passing a Keysight
calibration. I wonder if that's the experience of others that have bought
used 3458As and sent them to Keysight. If true, and I ever buy a 3458A, I
think I would only buy one on the condition that the seller  sends it to
Keysight, I pay the calibration cost, but if it fails, I get a full refund,
including the calibration cost.

I can understand a meter going out of spec over time, but if it can't be
sorted out without thousands of dollars spent on it, then it is not such a
good buy. But are more than 50% of 3458As like this?

Dave


Dr David Kirkby Ph.D C.Eng MIET
Kirkby Microwave Ltd
Registered office: Stokes Hall Lodge, Burnham Rd, Chelmsford, Essex, CM3
6DT, United Kingdom
Registered in England and Wales as company number 08914892
http://www.kirkbymicrowave.co.uk/
Tel 01621'680100 / +44 1621-680100
___
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

Re: [volt-nuts] Any list members in UK who can accurately characterise a 732A and a 10K resistor

[Dr. David Kirkby]

On 14 January 2018 at 15:40, David C. Partridge <
david.partri...@perdrix.co.uk> wrote:

> I've recently rebuilt a 732A and it seems stable, but what I don't know is
> its actual output voltage down to the last ppm
>
> I've also acquired a Guildline 3330 10K standard resistor but again don't
> know its value - my 3458A says it is 10,000.43 ohms which I find rather
> hard
> to believe (way out of spec.).
>

Is there a tight spec on the nominal value?

I can't find the specification on those from a Google search, but I thought
the actual value was not very well controlled, but the stability is. So the
fact it is 0.43 Ohms high, may not mean it is out of spec.

I would imagine there's a trade-off between getting the initial value
correct and the stability. If you design the resistor for maximum
stability, you may not be able to simultaneously get the value close to its
nominal value. It you do things to get the nominal value better, they may
degrade the stability.


>
> I know someone with a recently calibrated 3458A (Keysight Calibration, not
> accredited, not Loveland), but can anyone do better?  I'd prefer not to
> have
> a pay for a formal cal lab report on these.
>

A non-accredited Keysight calibration should be no less accurate than an
accredited Keysight calibration.  From what I understand, the procedure is
the same, but you just get a few extra words on the cal certificate if it
is accredited - and pay quite a bit more. It costs Keysight money to be
accredited, so they pass the costs of that onto people that need an
accredited cal certificate.

I wonder what ones chances of going to NPL on their open-day (17 May 2018)
and getting a measurement performed as a favor?  If you don't want an
official cal certificate, but just a number you scribble on a bit of paper,
you might be able to get it done free of charge. I know the lab with a
primary voltage standard (Josephine Junction), was open to the public on
the last open-day, which was in 2016. I don't think there was any lab open
that measured resistors though.


> Thanks
> Dave
>

Dave
___
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

[volt-nuts] Solartron (aka Schlumberger) 7081

[Dr. David Kirkby (Kirkby Microwave Ltd)]

I've been offered a Solartron 7081 8.5 digit meter, but are having
difficulty finding out much about this. Is there any "official" place where
these can be calibrated? As far as I can see from a search of Companies
House

https://beta.companieshouse.gov.uk/company/02858371

Solartron Instruments Ltd was dissolved in 2013. I don't know if there is
really anybody able to calibrate these things.

Clearly the meter is not in the same league as a 3458A. but I've been
offered it for little more than the cost of a new Keysight  U1282A 4.5
digit handheld meter! I've no idea when it was last calibrated, but I
suspect long ago.




Dr. David Kirkby Ph.D CEng MIET
Kirkby Microwave Ltd
drkir...@kirkbymicrowave.co.uk
http://www.kirkbymicrowave.co.uk/
Tel: 01621-680100 <01621%20680100> / +44 1621-680100 <01621%20680100> (0900
to 2100 UK time)

Registered office: Stokes Hall Lodge, Burnham Rd, Althorne, Essex, CM3 6DT,
UK.
Registered in England and Wales, company number 08914892.
___
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

Re: [volt-nuts] Power consumption of 3458A reference board / fitting one in a 3457A

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 23 September 2017 at 18:03, Tom Knox  wrote:

> If you want I will send you a few to play with for a few months.
>

Thank you very much. I'd like to have a play. I sent you a private email.

Someone suggested using the DCV:DCV ratio mode to look at two references,
but I don't see this facility on the 3457A. I think the only way to compare
two of them would be to put them in series, but back-to-back to subtract
the voltages, and look at the difference on the 3457A.


>
> Thomas Knox
>

It's odd there's someone selling LTZ1000A chips on eBay at $50 each.

http://www.ebay.com/itm/1x-LTZ1000ACH-Ultra-Precision-Reference-LTZ1000A-/111325506311

It looks like they have been removed from PCBs with a sledge hammer - they
are heavily scratched and/or dented. The sellers seems to have sold quite a
few, yet the chips are only marginally more expensive if bought new from
the manufacturer.

Dave
___
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

[volt-nuts] Power consumption of 3458A reference board / fitting one in a 3457A

[Dr. David Kirkby (Kirkby Microwave Ltd)]

I've got two different, but not totally unrelated questions.

1) Does anyone know what is the power consumption of the 3458A reference
board? I was thinking of getting one, boxing it up with a battery, that
allowed it to keep running without mains power. I would like to know the
energy storage the batteries would need to keep it running for 2 days.

2) Would there be any point fitting a similar board, with an LTZ1000A in a
3457A 6.5 digit meter? Would it be practical? I wonder if the drift on the
3457A's reference is significant, and so a LTZ1000A would be a worthwhile
upgrade. Or is the main drift not the voltage reference, and so such an
"upgrade" would be a total waste of time/money?

Dave
___
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

Re: [volt-nuts] Best way to measure micro Ohms

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 18 September 2017 at 23:28, george  wrote:

> The reason that DC is used commercially to measure resistance is simple,
> if you use AC you may well get the reactive component as well as the
> resistance coming into play.
>

That may not be an an issue with a dual-phase lock-in amplifier, as the
phase angle of the voltage can be resolved. In fact, it hints at something
I have long thought about - using a lock-in amplifier as an LCR meter. I do
however have a decent HP 4284A LCR meter, but it can't read very low
impedances in the micro ohm range.

I've put a couple of offers in on micro-ohm meters, but also bought a 150 W
public-address (PA) audio amplifier for £25 (around $35). With that, and
the lock-in amplifier, I should be able to make measurements, although I
accept the uncertainty will be higher than a dedicated micro ohm meter.


>
> Such low resistance measurements commercially are normally only made on
> high current power distribution networks as part of a periodic test regime
> where you need to determine the quality/resistance of such things as bus
> bar joints/connections and loop resistance.
>
> It is not a good idea to use copperslip around aluminium, there is an
> aluminium based version that should be used, but, be warned, just like
> copperslip it is an insulator, try putting your meter probes, set for
> resistance, into a tub of both, I have.  I do not know just why but the
> aluminium version is just like sand, it gets everywhere when you use it.
>

So does Coperslip! It sure is messy, but I was given it free, and it
stopped a leak.


>
> To check your joint I would use a four wire Kelvin set up using say 10
> Amps from my constant current bench supply and then use my Keithly 616
> digital  electrometer to measure the voltage/s present across the joint, a
> simple application of Ohms law will then give the resistance.
>

I don't have such an instrument, whereas the audio amplifier cost me very
little, and I already have the lock-in amplifier. I did buy a lower powered
(15 W, $5) amplifier from China, but thought by the time I box it up with a
PSU, it would cost more than a PA amplifier with a built in mains supply.
The PA amp, being in the UK, should also arrive a lot quicker than the
units from China.


>
> 73 George G6HIG
>

Dave, G8WRB
___
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

Re: [volt-nuts] Best way to measure micro Ohms

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 18 September 2017 at 18:36, Todd Micallef  wrote:

> Dave,
>
> Another meter is the Cambridge LOM-510A. I am not sure if it is in your
> budget but there has been a review made on EEVBlog. There is one currently
> on eBay with a current amplifier that I have never seen before today. It
> may be worth reviewing if it meets your needs.
>
> Todd
>


Hi Todd,
Something struck me as odd about the *model* number LOM-510A.

When I google the Keithley 580, I see a *paid advert* for an IET Labs
LOM-510A.

http://www.ietlabs.com/lom-510.html?gclid=CjwKEAjw3f3NBRDP_NHS9fq53n4SJACKIfEYZT_jyIk_TKn0gqEkzvfxwKASIpIZTcDFJfJlMwvnRRoCZYHw_wcB

But it looks nothing like the Cambridge LOM-510A on eBay

http://www.ebay.com/itm/Cambridge-510A-Micro-Ohmmeter-DLRO-Includes-NEW-leads-NIST-Calibrated-LOM-510A-/291956733548

It seems a bit odd for two manufacturers (IET Labs and Cambridge
Instruments) to both have the exact same model number (LOM-510A) for an
instrument with identical functionality (micro ohms). Yet photographs of
the two instruments show they look similar, but are not identical. The IET
Labs one appears to have a couple of extra switches.

Just to make something appear even more odd, the IET Labs has a link to a
review on EEVblog.

http://www.eevblog.com/forum/testgear/ie/30/

but the picture shows Cambridge Instruments, but the title shows IET Labs.



Dave
___
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

Re: [volt-nuts] Best way to measure micro Ohms

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 17 September 2017 at 21:58, Mitch Van Ochten <
mi...@vincentelectronics.com> wrote:

> The Keithley 2002 uses DC but automatically takes a reading of any offset
> voltage and subtracts it (offset compensation).  Rated accuracy on the 20
> ohm range (2 years) is +/- 26 ppm, and with 10 averages it has a resolution
> of 0.1 microohms.
>
>
> Best regards,
>
> mitch
>

Also very pricy!

I've made an offer on a Keithley 580 micro ohm meter, and ordered a couple
of $3 audio amplifier boards. I will try one with the lock-in amplifier. It
it does not work, or works poorly, it will not have broken the bank.

Dave
___
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

Re: [volt-nuts] Best way to measure micro Ohms

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 17 September 2017 at 20:12,  wrote:

> The question is what accuracy you need.
>

No a lot. I just want to find out if there's any voltage drops that are
significantly higher than I would expect. The unit makes an RF transmission
line, and the loss at RF is significantly higher than predicted by a
computer model, which takes into account the skin depth of the materials.
I'm wondering if there's something odd going on. I suspect the problem is
the current in the aluminum is not being computed properly due to the oxide
on the surface. But I just wanted to make sure there was no unexpected DC
resistance. I don't think there will be, but I want to climate that
possibility.


> The classical way to do that (achieving high accuracy) is to apply a known
> accurate current (say 10A) and measure the voltage drop accross the rod
> with a nanovoltmeter.
> As the piece of aluminum is isothermal you should not expect a big
> thermovoltage. You could also compensate for this by reversing the current
> and take the average, also by nulling the voltage reading prior to applying
> any current. Generating precisely known AC currents (low uncertainty) is
> difficult (i.e. measuring it precisely), therefore DC currents are ususaly
> used also in metrology for this.
> If you do some internet search you will find metrology reports about this.
> If you do not have a nanovoltmeter you could build a measurement amplifier
> with not that much of an effort (based on chopper amp or low drif precision
> opamp)
>

The only nV meter I have is the lock-in amplifier, which has a full-scale
sensitivity of 2 nV to 1 V in a 1-2-5 sequence.

The only instrument I have able to measure > 3 A of current is a handheld
multimeter. One of my power supplies can supply 35 A, and has an ammeter in
it. I don't have any particularly accurate means of measuring DC current
outside the limited of the 3457A.

In terms of simplicity, getting a $10 audio amplifier from China and using
the lock-in amplifier is the way to go, but I accept a metrologist would
not like that idea!

Dave
___
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

[volt-nuts] Best way to measure micro Ohms

[Dr. David Kirkby (Kirkby Microwave Ltd)]

I want to measure the resistance between two bits of aluminum. Each are 40
x 30 mm across. One is 250 mm long, the other is 8 mm long. I'm wondering
is surface oxides are on the faces, so despite being held together with
bolts, the resistance is perhaps not as long as I would expect. There's
also a layer of "copperslip" between these, to provide a waterproof joint.
That might be adding unnecessary resistance.

What sort of instrument is (if any) capable of measuring this? I have a 6.5
digits HP 3457A with a 30 Ohm 4-wire mode, but the uncertainty is 0.0065% +
20315 counts. Those 20315 counts are a lot!

I can't seem to see much in the way of commercial instruments for very low
resistance measurements. I would have thought an AC source was needed, yet
they all seem to use DC. Why?

I've thought of hooking a signal generator up to an audio amplifier capable
of driving a few amps, passing that through the joint, then using an EG
7260 lock-in amplifier to measure an AC voltage across the joint.

Any better suggestions?

Can anyone explain why commercial instruments use DC, despite that small DC
voltages will be developed by unwanted thermocouples? I would have thought
that using AC was a no-brainer no very low resistance measurements, but
commercial instruments don't use to use AC.


Dr. David Kirkby Ph.D CEng MIET
Kirkby Microwave Ltd
drkir...@kirkbymicrowave.co.uk
http://www.kirkbymicrowave.co.uk/
Tel: 01621-680100 / +44 1621-680100 (0900 to 2100 UK time)

Registered office: Stokes Hall Lodge, Burnham Rd, Althorne, Essex, CM3 6DT,
UK.
Registered in England and Wales, company number 08914892.
___
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

[volt-nuts] Anyone got a photo of a 3458A with "new volt" printed on it?

[Dr. David Kirkby (Kirkby Microwave Ltd)]

IIRC, there are reports of 3458A's being sent to Agilent, and having a
sticker to say the "new" standard volt was used - I assume the last time
the volt was redefined.

I was chatting to someone from my radio club in the pub last night, and
somehow we got onto the definition of a volt. I'd like to try to research
this, and perhaps give a talk at our radio club on it. I'd like to get a
picture of a 3458A with such a sticker if I could.

Dave


Dr. David Kirkby Ph.D CEng MIET
Kirkby Microwave Ltd
Registered office: Stokes Hall Lodge, Burnham Rd, Althorne, Essex, CM3 6DT,
UK.
Registered in England and Wales, company number 08914892.
http://www.kirkbymicrowave.co.uk/
Tel: 07910 441670 / +44 7910 441670 (0900 to 2100 GMT only please)
___
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

[volt-nuts] Don't bother changing a 3457A battery if sending to Keysight for calibration.

[Dr. David Kirkby (Kirkby Microwave Ltd)]

Today I went to Keysight in Winnersh in the UK for a seminar on RF material
measurements.

We were given the opportunity to go for a 20 minute tour of the repair and
calibration labs. Needless to say I took up the opportunity.

There are 3 areas at Keysight in the UK.

* Repair
* Main calibration area
* Metrology (which we didn't go into in order not to change the
temperature, but one can see a lot as its surrounded by glass)

I asked whether a 8.5 digit 3458A can be calibrated there,  since somewhere
I had heard that a 3458A could not be calibrated in the UK.  I was told a
3458A can be calibrated there.

I asked about calibration of a 6.5 digit 3457A, and wherever I should send
it for cal having just removed the battery, which loses the calibration
data, or hotwire it to save the calibration data. I was told that if the
battery is available,  and not more than £30~£40, then they would change
the battery free.

I mentioned that I was a little disappointed that when I sent an 4284A LCR
meter for a free software upgrade and calibration,  no data was provided
about the instruments state before the calibration.  I was told that if an
instrument is repaired or upgraded,  even if just a software upgrad, the
repair would normally happen in the repair section, before being moved to
the calibration area, so one will not get any data about the status when it
was received.

However,  if one asks for data before an item to serviced, they will
provide that, then service it,  then calibrate it and provide that data
too. Apparently there would be no extra cost.

I don't know how policies might vary at other Keysight cal labs, but I got
the feeling that at Winnersh in the UK,  they are quite flexible.

So I am going to send my 3457A for calibration,  but ask for

1) Data on condition as received.

2) The battery to be changed.

3) Condition after it's been calibrated.

I got the business card of the individual who said that this can all be
done for no extra charge.

Obviously Keysight is not the cheapest place to get a 6.5 digit 3457A
calibrated,  but it seems that you get quite a bit for your money.

Dave.
___
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

Re: [volt-nuts] PCB Artist

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 14 Dec 2016 14:14, "Dan Kemppainen"  wrote:
> If it's a one off board, with a handful of components anything should
work. You can always redraw it later in something else. If you have 500
components, differential signals, and controlled impedance stuff that's a
different story.

A handful of surface mount components can easily exceed 500!

But like you,  I find the idea of using an open source program much more
attractive.

Someone mentioned earlier about making PCBs on a milling machine. That
needs a different approach than to etching.  To reduce tool wear one should
leave as much copper on the board as possible,  removing only that which is
essential to keep.

Thinking of it logically,  leaving as much copper on the board as possible
will preserve the useful life of the etchant, but most people leave remove
as much copper as possible, except for RF boards.

Dave.
___
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

Re: [volt-nuts] Availability of 3458A in Europe after the end of 2016.

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 13 November 2016 at 14:17, Chuck Harris  wrote:

> RoHS does not apply to test equipment.
>

Where do you get that from? When I was looking briefly the other day, there
did not seem to be a lot of exemptions.

I'm sure Keysight must be a bit more on the ball than to put that notice,
if RoHS did not apply to test equipment.

There's a similar notice about a power supply I have - 6674A (70 V @ 30 A
PSU).

Dave
___
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

[volt-nuts] Availability of 3458A in Europe after the end of 2016.

[Dr. David Kirkby (Kirkby Microwave Ltd)]

The 3458A page on the Keysight website is interesting.

"Notice for European Union Customers: This product is not updated to EU
RoHS compliance and can be ordered via Keysight directly or Keysight
Authorized Distributors until 31 December 2016. Beyond this date, the
product can still be purchased from Keysight Authorized Distributors.
Please contact Keysight Authorized Distributors or your local Keysight
sales representative for quotation and ordering."

It seems you can't buy it from Keysight, but you can from their
distributors. But most times I've contacted Keysight about buying things,
they tell me to get them from their distributors anyway.

If I interpret


https://www.gov.uk/guidance/rohs-compliance-and-guidance

correctly, nobody should be stick non-compliant things in the EU market.

I can't be bothered to read in detail the

"DIRECTIVE 2011/65/EU OF THE EUROPEAN PARLIAMENT AND OF THE COUNCIL of 8
June 2011 on the restriction of the use of certain hazardous substances in
electrical and electronic equipment (recast)"

http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=OJ:L:2011:174:0088:0110:EN:PDF

as I some paint I want to watch dry. But a cursory glance shows exceptions,
but none seem relevant to a 3458A.

Dave
___
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

Re: [volt-nuts] low emf solder

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 29 October 2016 at 14:51, NeonJohn <j...@neon-john.com> wrote:

>
>
> On 10/28/2016 08:39 PM, Dr. David Kirkby (Kirkby Microwave Ltd) wrote:
>
> > I wonder how practical it is to weld test leads, so there's no solder or
> > thermal EMF.
> >
> > I know that this will sound crazy, and probably is, but could one weld
> > components to a PCB?
>
> Yes indeed.  About 20 years ago I had a machine that made circuit board
> by routing tiny wires and spot welding them to the connection.  I can't
> for the life of me remember that process name.
>
> Only problem is, if you weld two different metals together, even copper
> with different compositions, you've still made a very rugged and durable
> thermocouple.
>
> John
>

But if one could use copper as the bond wire, rather than gold which is
quite common, then it would give you very little thermal EMF

I would have thought any impurities in copper wire, would be quite small,
as it would reduce the electrical conductivity. Whilst I accept one is not
going to get 100.00 % pure copper, I would have thought
the effect of any impurities at least an order of magnitude less than using
solder. I'm only postulating this - I have no evidence to back it up, and
have never studied the subject.

Perhaps the person who was making the measurements on the solder, could try
making a thermocouple by welding two bits of wire taken from different
sources. I guess the problem would be preventing any impurities entering
the weld. A quick Google suggests one needs argon gas when welding copper.

Dave
___
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

Re: [volt-nuts] low emf solder

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 28 Oct 2016 15:25, "Juris L"  wrote:
>
> Found reference to optimal emf solder composition cadmium/tin alloy
> (70 %/30 %) in JJ array measurement article page 12.

I wonder how practical it is to weld test leads, so there's no solder or
thermal EMF.

I know that this will sound crazy, and probably is, but could one weld
components to a PCB?

I don't even have the excuse of been drunk or taking drugs,  but I will
risk ridicule for making the above comment!  Sometimes thinking out of the
box is useful.

Dave.
___
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

Re: [volt-nuts] Is there a "standard" much better than a LTZ1000, but much cheaper than a Josephson Junction Array?

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 20 October 2016 at 00:08, Poul-Henning Kamp <p...@phk.freebsd.dk> wrote:

> 
> In message  g...@mail.gmail.com>
> , "Dr. David Kirkby (Kirkby Microwave Ltd)" writes:
>
> >The question about the Josephson Junction Array got me thinking. I wonder
> >if there are any sort of technologies that can produce a voltage with much
> >better stability than the LTZ1000, but without the cost of a Josephson
> >Junction Array. A sort of half-way house.
>
> As far as I know there are only two steps between the LTZ1000 and JJAs:
>
> 1. Specially cared for LTZ1000's (See: Fluke)
>

Do you have a specific reference?  A google found lots of kits on Fluke and
LTZ1000,  but none of the pages were from Fluke.


> 2. Lots of LTZ1000's to get sqrt(N) reductions.
>


> --
> Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
>


But that assumes the drifts are completely uncorrelated, which I doubt is
the case - especially if they are all from the same batch. But there are a
limited number of resistors of the quality needed (Vishay is the only one I
can think of), and PCB materials are likely to be the same. It seems to me
that you would not gain sqrt(N) unless N is quite small. How small, is
anyone's guess.

Dave
___
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

[volt-nuts] Is there a "standard" much better than a LTZ1000, but much cheaper than a Josephson Junction Array?

[Dr. David Kirkby (Kirkby Microwave Ltd)]

The question about the Josephson Junction Array got me thinking. I wonder
if there are any sort of technologies that can produce a voltage with much
better stability than the LTZ1000, but without the cost of a Josephson
Junction Array. A sort of half-way house.

BTW, I see some rather battered up LTZ1000A's on eBay,

http://www.ebay.com/itm/1x-LTZ1000ACH-Ultra-Precision-Reference-LTZ1000A-/111325506311

that have dents in them. They are more expensive than buying the chip new
from the Linear Technology website.

http://www.linear.com/purchase/LTZ1000

Yet people seem to buy them. Now I know the stability of those improve with
age, but when they have dents in them, its clear they have not been exactly
cared for. Maybe I will buy some new LTZ1000As and stick them on eBay for
$100 and see how many I sell !!

It seems the real cost of an LTZ1000A standard is not the chip, but the
resistors you need.
___
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

Re: [volt-nuts] Low-cost Josephson Junction Array

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 19 October 2016 at 20:15, Ken Peek  wrote:

> Well, I already have a 3458A,


OK, quite an expensive multimeter. Otuside my budget for something I don't
really need, but would like!


  $400K is *WAY* out of my budget.  I was looking more for
> something on the surplus market-- or some "cast away" JJA that someone is
> getting ready to throw into the dumpster-- something that nobody wants
> anymore that I can get working on a _very_limited_ budget...


It might be worth mentioning how much money you are willing to spend on it,
as it may give people ideas about what could possibly be done yourself, and
what is just not going to be practical.

You may well find getting liquid helium impossible. Here in the UK it is
very difficult to get chemicals dangerous chemical if you are not on an
industrial site. I very much doubt British Oxygen Company (BOC) would
delivery liquid helium to my house.


Stage 1 would be to see what you would need in order to get the He
delivered. Without that you are not going to get anywhere, and I doubt you
will get that delivered unless you have vessels that have been properly
maintained.

I would imagine that just getting the stuff delivered would be next to
impossible without spending a lot of money, especially in the USA.
___
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

Re: [volt-nuts] Calibration of 34401A

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 12 Oct 2016 10:31, "Poul-Henning Kamp"  wrote:
>
> 
> In message <120112818.2234439.1476263954...@mail.yahoo.com>, Bruce
Griffiths wr
> ites:
>
> >Does anybody know if a 34401A can be adjusted by a competent 3rd party
lab,
> >or are the details of how to adjust the meter not available outside of
> >Keysight?
>
> The service manual has the calibration procedure, and it is all software.
>
> --
> Poul-Henning Kamp   |

Cheers.  It seems that the lab is incompetent then, as none of the values
appeared to be in a massive difference
___
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

[volt-nuts] Calibration of 34401A

[Dr. David Kirkby (Kirkby Microwave Ltd)]

I have a 'friend" (actually a person who I have never met, but is a pain in
the ***).

He sold a Agilent 34401A multimeter which the customer said is out of
specification and can not be adjusted.

Quickly scanning the measurent results,  the  meter is not showing results
with any huge errors  (say 1%), but which (if any) range it is out of
specification I don't know. Unlike the Keysight calibration certificates I
have seen, the measurement results doesn't show the upper and lower limits
for the specification of the meter,  so one can not tell from a quick
glance if the meter is out of specification. One would need to study the
detailed specification.

*IF* I understand correctly, (and the data is in Spanish which I don't
speak),  with an input of 9,0 V, the meter reads 9,99899 which  the
data  indicates is an error of  -91 uV/V with an uncertainty of 7.7 uV/V.

The lab said the meter can not be adjusted.  I don't know if they mean

1) This lab has no ability to adjust the meter.

OR

2) It is too far off to adjust.

Does anybody know if a 34401A can be adjusted by a competent 3rd party lab,
or are the details of how to adjust the meter not available outside of
Keysight?

Dave
___
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

Re: [volt-nuts] Keysight 3458A vs Keithley 2002 8.5 digit multimeters.

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 18 Jul 2016 17:34, "John Phillips"  wrote:
>
> Most labs never turn 3458As off. The longer they are on the lower the
drift
> rate. I would rather have an 20 year old meter with new batteries than a
> new meter.

If one buys a used meter, one has no idea if it has been switched on very
occasionally or on 24/7.

Do you keep your meter powered up during the transit between your lab and
the cal lab? I would think that quite difficult if you used a courier,  but
not a problem if it was taken in a car.

Dave.
___
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

Re: [volt-nuts] Keithley 2001 - do you need to open it to calibrate it?

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 26 June 2016 at 20:46, Todd Micallef  wrote:

> David,
>
> I have found that many sellers like to remove any calibration stickers or
> tamper evident stickers. Not sure why they do that as a sticker does not
> mean the item is calibrated.
>

The sticker on the front has been removed, but the one underdeath, which
covers a screw, is still there, but the screw has clearly been undone, so
the seal is "broken". I'm interested to know if it is necessary to undo the
case to calibrate the 2001, or whether it can all be done from the front
panel, probably removing that sticker on the front.

There are a few things I am not happy about this - the front panel appear
to move far more than I would expect. Depressing one key seems to make
several keys nearby go retreat towards the back of the unit, although it
appears to function.

I was a bit surprised when I put it on the 2 A range, with no leads
connected, the current is showing as high as 6 mA at times. This seems odd
given the current is obviously zero. I realize leaving the leads open on
voltage is going to lead to undefined results, but I would have expected on
current for the meter to read very close to zero.

If I put it on "auto", on DC current, with no leads, the reading is going
as high as 20 nA - there's noise on the last 3 digits. I don't know if that
makes any sense. The update rate is very fast, so perhaps that's to be
expected unless one increases the integration time.

But there are a few things making me think this meter might have issues. A
rather strange smell was initially evident, but that seems to have cleared.
The movement of the keys seems very odd. I will almost certainly return
this.


>
> If you have 14 days, run it through the paces and perform self-tests. There
> are some test scripts here https://xdevs.com/article/dmm_noise/ to see if
> the meter is measuring close to others.
>

Thanks, I will take a look.

My computer that has the GPIB board in is is rather sick at the minute. I
need to sort out what is wrong with it, as its the only convenient computer
to have a controller card in.

Dave
___
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

Re: [volt-nuts] Thermal EMF of common solder

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 26 June 2016 at 15:12, Andrea Baldoni  wrote:

> Hello All.
>
> I measured the thermal EMF of two common solder, the lead free
> Sn96.5/Ag3/Cu0.5 and the old Sn60/Pb40.
>

Please excuse my ignorance, but how do you mean the thermal EMF of solder?
Do you not need another metal, such as copper to make a junction? If so,
you are measuring the emf

Dave
___
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

[volt-nuts] Keithley 2001 - do you need to open it to calibrate it?

[Dr. David Kirkby (Kirkby Microwave Ltd)]

I got the 2001 that I ordered yesterday. There are a few things that make
me feel uneasy about it, so I will probably return it.

The calibration seal is missing off the front, which is obvious from the
eBay photo, but also one at the bottom which looks as though one needs to
open in order to get inside the unit. That had a seal, but has been broken.
I'm wondering if that would be a normal part of the calibration routine, or
if someone has opened this up after it was calibrated.

The cal was due "Jan/12/10", which I assume means the 12th of January 2010.

Also, although when I see the pictures on eBay I never noticed it, a closer
inspection of the photos .

http://www.ebay.co.uk/itm/KEITHLEY-2001-DMM-/152113460174

does show that the hole on the front where a calibration seal would be
placed, has at one time in the past had a device too large pushed into the
hole. The hole is no longer round as I would expect it to be.
___
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

Re: [volt-nuts] LTZ1000 project build

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 4 Jun 2016 20:44, "Poul-Henning Kamp"  wrote:
>
> 
> In message <57527f8a.6070...@yandex.com>, Charles Steinmetz writes:
>
> >As I have mentioned before, for many years I have put precision circuits
> >that may be sensitive to humidity into gasketed metal boxes with fresh
> >silica gel packets.

> Only thing to remember is that it also reduces air circulation in the
> box and therefore increases thermal gradients.

I don't know how practical they are, but I have see humidity calibration
standards (e.g 50%). These  use a chemical reaction to keep a volume at a
constant humidity.  That might be a way of keeping the humidity constant,
without introducing increasing thermal gradients.

They might introduce a whole host of other problems,  so such a method
would need researching.

If a new PCB was designed,  it would be nice if there were pads to take the
expensive Vishay foil resistors,  in addition to a cheaper choice.

Dave
___
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

[volt-nuts] Suggestions for 10 milli Ohm 0.04 % 100 W resistor

[Dr. David Kirkby (Kirkby Microwave Ltd)]

I have an HP 6674A power supply with option J06,  which means that the PSU
is 70 V @ 30 A rather than the standard 60 V @ 35 A .

I've replaced a couple of bits in this and will need to replace some more,
so it would be prudent to get this calibrated.

The service manual calls for a 8.5 digit 3458A, which seems a bit over the
top given the displays for voltage and current are only 4 digits. I think
my 6.5 digit 3457A will be good enough. This is a 2.1 kW PSU, not a
precision measuring instrument. But I don't have any ammeter that can read
30 A, so I can not just use an external ammeter if I want to know the
current.

The service manual also calls for a 0.010 Ohm 0.04 % 100 W resistor, with a
recommended resistor of a Guildline 9230/100. I am wondering how practical
it is to make such a resistor and verify its performance on the 3457A.
Some versions of this PSU have a lower output voltage (56 V) but higher
current (42 A). With the 30 A PSU I have,  the maximum power that could be
dissipated in a 0.01 Ohm resistor is obviously 9 W.

Any suggestions about what I can use that will not cost a fortune?

Looking on eBay, Guildline resistors are several hundred USD each. I can't
justify that given the cost of a Keysight calibration of the PSU is $199 in
the USA.

I much admit that I have never really much attention to calibration of a
PSU. It seems a bit of a waste of money when you can use a decent
multimeter if you really want to know the voltage or current. But with a
PSU of this size, I don't have an ammeter good enough.

The other tricky bit about calibration of this PSU is the need for loading
it to full power (2.1 kW) then dropping the load to 50% and measuring the
recovery time. It should recover to within 100 mV in 900 us. Likewise it
should recover the same if switched from 50%  of load to 100 %. The manual
calls for an electronic load,  but I suspect a FET switch and some big
resistors in water will do. I don't see any need for such resistors needing
to be very high precision, but obviously something decent is needed to
calibrate the ammeter.

Dave.
___
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

Re: [volt-nuts] Just back from cal

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 8 Apr 2016 04:21, "Joseph Gray"  wrote:
>
> In February, I sent my HP 3457A in for cal. In late March, I sent my
> EDC VS330 DC Voltage Reference in for cal. Today, I just got the VS330
> back and thought I'd compare the two instruments.

Did you send them to the manufacturers or a third party lab? I am
personally VERY skeptical of the competence of a number of so-called
calibration labs. A few months back there wss a 40 GHz vector network
analyser on eBay for auction which included a cal certificate.  The
certificate listed the items used for the calibration.  The calibration kit
used was a 6 GHz economy type N kit made by HP. The N connector will not
work properly at 40 GHz, but even if it did,  the use of a calibration kit
is insufficient to calibrate a VNA.

I have seen countless examples of this sort of thing. I would not
personally consider getting any of my HP kit calibrated by anyone other
than Keysight.

> Both instruments have been on for a couple of hours. It is about 25 C
> in the room.

That is quite warm.  Are both specified at that temperature?

> Setting 10.0 on the VS330, I measure 9.99891 VDC on the 3457A.

I would try to find a local volt-nut with a 3458A.

I would also keep a log of the differences between your voltage standard
and multimeter.  If the difference is changing significantly over time, it
would tend to indicate one or both are unstable.  If however the difference
remains very similar then I would be more suspicious that one is
incorrectly calibrated.

> The report on the 3457A, dated 16 Feb says the 30 VDC range read
> 29.9991 VDC. The report on the VS330, dated 31 Mar says 10 VDC read
> 10.0001 VDC. Both instruments required adjustment.

I have heard several reports of 3457As being in spec many years after they
were last calibrated.  The fact your unit required adjustment seems a
little unusual.

If the VS330 was out by 1  on the last digit,  that suggests to me it
didn't require adjustment.

> These numbers would lead me to believe that I should be getting a lot
> closer agreement to 10 VDC for both of these instruments. Am I
> expecting too much?

I have not checked your numbers,  but would agree if both units have been
recently calibrated,  the agreement between the two should not be just
inside the limits if you take the worst case of each. I would expect much
closer agreement.

If the two appear to be drifting with respect to each other the the
purchase of another 3457A, even if uncalibrated,  would probably allow you
to determine what one of your

> Joe Gray
> W5JG

Dave, G8WRB.
___
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

Re: [volt-nuts] 3457A - should I preserve SRAM contents, or purposely corrupt them by removing power?

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 25 January 2016 at 11:12, Dr. David Kirkby (Kirkby Microwave Ltd) <
drkir...@kirkbymicrowave.co.uk> wrote:

> As noted in another thread, I want to replace a battery in a 3457A that
> has not been replaced in at least 11 years. The instrument has not been
> calibrated in that time either. At the time it was purchased from a dealer,
> I was told it was within specification, but if I wanted it calibrated I
> would need to pay. I never did have it calibrated, so have no historical
> data about this. I've no idea when it was calibrated, and have no cal
> certificate, so have no idea of the errors at the time of calibration.
>
> I now want to change the battery, *and* send it to Keysight for
> calibration - I have a healthy skepticism of 3rd party labs, so would
> rather pay more and get the job done by Keysight.
>
> I'm wondering if I would be better purposely removing the battery, and
> putting a short across the SRAM so I ensure the contents are definitely
> lost. My logic is that
>
> 1) If I send it to Keysight and the cal data is corrupt, they will set the
> meter correct.
>
> 2) If sent to Keysight, with the cal data in tact, then if its within
> specification they will not adjust it. So if the limit on some parameter is
> 1%, and the error is 0.5%, then it will not be adjusted. But if the SRAM is
> corrupted, the error will be huge (if it will read at all), so it would
> force Keysight to adjust it to the correct value.
>



> At that point the error should be effectively zero
>


> Thoughts?
>

Someone sent me a private email, saying that if by purposely removed the
power from the SRAM  caused the 3457A to fail its self-tests, which is may
well do, then Keysight may consider the 3457A needs repair, and so offer a
fixed-price repair. Hence my "trick" to get this calibrated as accurately
as possible would have backfired, and I'd be out of pocket. In fact, on a
3457A, the fixed-price-repair would probably cost more than the instrument
is worth, as these are not worth a lot now.

Hence I would not do this before getting clarification from Keysight. It
might be possible to get them to set it right, even if within spec, but I
think their calibration routines are very automated, so its probably not so
easy to get a special calibration, whilst paying for their cheapest
calibration service.

Dave
___
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

[volt-nuts] 3457A - should I preserve SRAM contents, or purposely corrupt them by removing power?

[Dr. David Kirkby (Kirkby Microwave Ltd)]

As noted in another thread, I want to replace a battery in a 3457A that has
not been replaced in at least 11 years. The instrument has not been
calibrated in that time either. At the time it was purchased from a dealer,
I was told it was within specification, but if I wanted it calibrated I
would need to pay. I never did have it calibrated, so have no historical
data about this. I've no idea when it was calibrated, and have no cal
certificate, so have no idea of the errors at the time of calibration.

I now want to change the battery, *and* send it to Keysight for calibration
- I have a healthy skepticism of 3rd party labs, so would rather pay more
and get the job done by Keysight.

I'm wondering if I would be better purposely removing the battery, and
putting a short across the SRAM so I ensure the contents are definitely
lost. My logic is that

1) If I send it to Keysight and the cal data is corrupt, they will set the
meter correct.

2) If sent to Keysight, with the cal data in tact, then if its within
specification they will not adjust it. So if the limit on some parameter is
1%, and the error is 0.5%, then it will not be adjusted. But if the SRAM is
corrupted, the error will be huge (if it will read at all), so it would
force Keysight to adjust it to the correct value. At that point the error
should be effectively zero given its a 6.5 digit multimeter, which means
the uncertainly in Keysight's measurements should be much lower than the
uncertainty of my meter.  So by corrupting the SRAM, I should get a meter
returned to me that is more accurately calibrated than if I take the
trouble to preserve the SRAM contents.

3) The adjustments are I believe software, so there's no risk that
adjusting potentiometers will cause drift to increase.

4) I don't have any historical data from cal certificates, so even if I a
range is in error by 0.5%, I can't make any attempt to estimate the drift
over time. Clearly if I had cal certificates over a period of years, I
maybe able to get some idea of how the instrument is drifting, so possibly
correct for that, if it is drifting in one direction.

Thoughts?

Dr. David Kirkby Ph.D CEng MIET
Kirkby Microwave Ltd
Registered office: Stokes Hall Lodge, Burnham Rd, Althorne, Essex, CM3 6DT,
UK.
Registered in England and Wales, company number 08914892.
http://www.kirkbymicrowave.co.uk/
Tel: 07910 441670 / +44 7910 441670 (0900 to 2100 GMT only please)
___
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

Re: [volt-nuts] Wanted - UK source of a replacement battery (type LX 1634) for HP 3457A 6.5 digit multimeter

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 25 January 2016 at 15:23, Andrea Baldoni <erm191...@ermione.com> wrote:

> On Sun, Jan 24, 2016 at 07:54:34PM +0000, Dr. David Kirkby (Kirkby
> Microwave Ltd) wrote:
>
> > I've got a HP 3457A 6.5 digit multimeter - S/N 2703A04579. It's working
> > fine, but I'm aware the battery must be at least 11 years old, as I first
> > bought the meter 11 years ago. I suspect its due for a change.  I'm
> trying
> > to find a *reputable* source for a replacement. I want to avoid eBay, due
> > to the number of fakes on there.
>
> Hello David.
> If the Panasonic replacement is good, you can buy the equivalent Varta
> 06127201301 from RS (their code is 240-9437).
>
> http://uk.rs-online.com/web/
>
> Best regards,
>  Andrea Baldoni
>


It is the same general type, but the pinout is wrong. Mine has two radial
pins, not 3. That will not fit.

Dave
___
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

Re: [volt-nuts] 3457A - should I preserve SRAM contents, or purposely corrupt them by removing power?

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 25 January 2016 at 15:40, Poul-Henning Kamp <p...@phk.freebsd.dk> wrote:

> 
> In message <
> canx10halwjxt+8ev8lywdqy9eez+anawihgqeyrzntsy80v...@mail.gmail.com>
> , "Dr. David Kirkby (Kirkby Microwave Ltd)" writes:
>
> >I'm wondering if I would be better purposely removing the battery, and
> >putting a short across the SRAM so I ensure the contents are definitely
> >lost. My logic is that
>
> I would save the content before doing that, so that I could compare it
> to whatever I got back from calibration.
>
> My experience so far says that there probably is a GPIB command which
> can read out the memory, but of course you still need to know the
> address-space layout.
>

I've not looked myself, but I did see a note on the web there was no
documented command to do read out the cal data on a 3457A. But in any case,
unless I know how to interpret those values, a bunch of meaningless 0's and
1's is not going to be a lot of use. Of course, if I could save them I
would, then in the event someone ever figures out what the numbers mean, I
could do a comparison.

It would be nice to know if the meter is in/out of spec, but to me, I think
having it put as close as possible to correct is more worthwhile, even
though a metrologist who gets their meter calibrated regularly would no
doubt see it different.


Dave
___
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

Re: [volt-nuts] Wanted - UK source of a replacement battery (type LX 1634) for HP 3457A 6.5 digit multimeter

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 25 Jan 2016 03:51, "Tom Miller"  wrote:
>
> Looking through the service manual I don't see a connection from the
battery to the NVRAM. I am sure I measured battery voltage on pin28 so I
suspect a schematic error. Can someone that has one open verify that? My
3457 is in cal and I prefer not to break the seals.

NVRAM (non-volatile random access memory), an example of which is flash
ram, doesn't need any power source to hold the data.  The 3457A has SRAM
(static random access memory), which does.

Using my old Tektronix 4.5 digit multimeter I definitely measured a voltage
on positive voltage on pin 28 which was around 200 mV less than the
battery.  I believe it must be via a high impedance path as my meter, which
I assume is 10 M Ohm input impedance,  is loading the circuit and so one
sees the voltage drop slowly although the battery voltage doesn't change.

When I put the mains power on, the voltage on the SRAM rose to about 4.8 V.
When the mains power is removed the voltage stays well over 4 V but
gradually drops in voltage.  I assume that a decoupling capacitor has been
charged to 4.8 V, so the voltages across the SRAM doesn't immediately fall
back to 2.8 V. Without having acess to an electrometer or other very high
input Z multimeter I could not say for sure, but I suspect that if one was
fairly quick (of the order of minute or two) one could probably just cut
the old battery out, solder a new one in, without loosing the contents of
the SRAM. But one would not want to take that chance if one considered it
was important to keep the data.

I am actually thinking whether it is better for *me* to actually purposely
let the SRAM contents be lost, but my reasons for this world form another
thread.

Dave.
___
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

[volt-nuts] Fall of SRAM voltage in a 3457A without external power

[Dr. David Kirkby (Kirkby Microwave Ltd)]

I decided to try a little experiment on my 3457A, When on mains the SRAM
gets 4.8 ~ 5 V. This does not seem to be well regulated, so I assume
depends on mains voltage. Once power is removed, the voltage on the SRAM
stays well above the battery voltage for some considerable time, which I
assume is due to a decoupling capacitor. My 10 M Ohm input Z multimeter is
loading the circuit too much to continuously monitor the voltage, but a few
checks indicated the voltage across the SRAM is falling quite slowly.
Starting at 4.8 V from mains power, after 23 minutes of no mains power, the
voltage on the SRAM was at 3.4V, which is above the battery voltage (3.03
V). and well above the 2.0 V needed to hold the SRAM contents. Assuming the
SRAM takes a constant current one would expect the voltage to fall linearly
with time. If so, it would take 46 minutes to fall to 2.0 V even without
battery power.

ESD and leakage of the human body would probably make screw this up, so I'm
not suggesting replacing the battery that way if you want to preserve the
contents of the SRAM, but there's a fairly good chance the contents would
remain in RAM if one was reasonably quick, especially if you topped the
voltage up from the mains just before removing it from the chassis.

Dr. David Kirkby Ph.D CEng MIET
Kirkby Microwave Ltd
Registered office: Stokes Hall Lodge, Burnham Rd, Althorne, Essex, CM3 6DT,
UK.
Registered in England and Wales, company number 08914892.
http://www.kirkbymicrowave.co.uk/
Tel: 07910 441670 / +44 7910 441670 (0900 to 2100 GMT only please)
___
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

Re: [volt-nuts] Fall of SRAM voltage in a 3457A without external power

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 25 January 2016 at 11:50, Poul-Henning Kamp <p...@phk.freebsd.dk> wrote:

> 
> In message <
> canx10hcamahhhxqiao9bdzu03c2bbt787mr10rmnywk3oa8...@mail.gmail.com>
> , "Dr. David Kirkby (Kirkby Microwave Ltd)" writes:
>
> >ESD and leakage of the human body would probably make screw this up, so
> I'm
> >not suggesting replacing the battery that way if you want to preserve the
> >contents of the SRAM, but there's a fairly good chance the contents would
> >remain in RAM if one was reasonably quick, especially if you topped the
> >voltage up from the mains just before removing it from the chassis.
>
> I usually hook up a separate battery while doing such surgery.
>


Yes, it is the logical thing to do, but there's a reasonable chance one
could get away with it, but obviously if its important to keep the data,
one would use an external supply. I'm tempted to purposely let the data
become corrupted for the reasons I gave in another thread.

Dave
___
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

Re: [volt-nuts] Wanted - UK source of a replacement battery (type LX 1634) for HP 3457A 6.5 digit multimeter

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 24 January 2016 at 21:24, Poul-Henning Kamp <p...@phk.freebsd.dk> wrote:

> 
> In message <
> canx10hadbw1u9ejc8_zgsk94k8az8vzg4ose+xngfwrali0...@mail.gmail.com>
> , "Dr. David Kirkby (Kirkby Microwave Ltd)" writes:
>
> >Opening the meter up, I see the PCB shows "BT 601". There's no name on the
> >battery I can see, but the type number of LX 1634. The voltage measured on
> >my 4.5 digit handheld DVM is 3.03 V. Googling around
>
> My guess is that this is a 3.6V Lithium-Thionyl battery, and if it is
> only 3.03V now, you're very likely tethering right on the brink.
>
> The most reputable vendor in this space is Tadiran, and they charge
> accordingly.
>


The post by Glenn (WB4UIV) in the link

https://groups.yahoo.com/neo/groups/hp_agilent_equipment/conversations/topics/48964

does say that it is Lithium-manganese dioxide (Li-MnO2). That information
was apparently taken from the battery manufacturer's web site. So I don't
think it is a Lithium Thionyl Chloride cell, although I'm very tempted to
fit one, as I can get one easy enough and I can't see the extra voltage
would do any harm given the SRAM is 5 V. The SRAM actually gets about 4.8 V
when on mains, so even a fresh Lithium Thionyl Chloride cell, which would
be more than 3.6 V off load, would not be too much for the SRAM. So I think
I am safe for now, but given the cell is at least 11 years old (probably
much older), it is living on borrowed time.

Dave
___
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

Re: [volt-nuts] Wanted - UK source of a replacement battery (type LX 1634) for HP 3457A 6.5 digit multimeter

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 24 January 2016 at 22:16, Poul-Henning Kamp <p...@phk.freebsd.dk> wrote:

> 
> In message <
> canx10hcknsnxczjx8gccd2-t0j-jom7ybmncgdvis9ic3yv...@mail.gmail.com>
> , "Dr. David Kirkby (Kirkby Microwave Ltd)" writes:
>
> >The SRAM actually gets about 4.8 V
> >when on mains, so even a fresh Lithium Thionyl Chloride cell, which would
> >be more than 3.6 V off load, would not be too much for the SRAM. So I
> think
> >I am safe for now, but given the cell is at least 11 years old (probably
> >much older), it is living on borrowed time.
>
> The one footnote to that is that some SRAMs go into a special "hibernate"
> state when VCC drops below a certain threshold.  If this SRAM has that,
> you want to make sure the threshold is above the battery voltage.
>

Thank you. That is certainly important if that's the case. I can't seem to
find a data sheet on the exact SRAM in my 3457A (Toshiba TC5564PL-15), so
difficult to know.

Dave
___
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

[volt-nuts] Wanted - UK source of a replacement battery (type LX 1634) for HP 3457A 6.5 digit multimeter

[Dr. David Kirkby (Kirkby Microwave Ltd)]

I've got a HP 3457A 6.5 digit multimeter - S/N 2703A04579. It's working
fine, but I'm aware the battery must be at least 11 years old, as I first
bought the meter 11 years ago. I suspect its due for a change.  I'm trying
to find a *reputable* source for a replacement. I want to avoid eBay, due
to the number of fakes on there.

Opening the meter up, I see the PCB shows "BT 601". There's no name on the
battery I can see, but the type number of LX 1634. The voltage measured on
my 4.5 digit handheld DVM is 3.03 V. Googling around

https://groups.yahoo.com/neo/groups/hp_agilent_equipment/conversations/topics/48964

would suggest the battery was made by Saft and is a Lithium-manganese
dioxide (Li-MnO2). The size appears to be known as 2/3A. One source
suggests a replacment is the Panasonic BR-2/3AE2SP

Mouser's uk site
http://www.mouser.co.uk/
says shipping is restricted, so only available in the USA.

The nearest I've found to anything remotely suitable is actually a 3.6 V
battery

"CROMPTON ETERNACELL  T32/8AA8F  Battery, Single Cell, Lithium Thionyl
Chloride, 2100 mAh, 3.6 V, 2/3A, Axial Leaded, 16.3 mm"

http://uk.farnell.com/crompton-eternacell/t32-8aa8f/battery-lithium-2-3aa-axial-lead/dp/774017

I'd rather not fit a higher voltage battery, although given it provides
power to some 5 V static RAM, I would not expect it to be a problem. That
said, I believe when on mains power this battery is not needed, so there
may be some circuitry that would not like a 3.7 V battery. When power is on
the unit, there is 4.88 V across the static RAM. As mains is reduced, so
the voltage drops to about 2.8 V. I think there must be a Schottky diode
that stops the battery being drained when the mains power is on.

The battery needs to have either very thin pins or wire-ended. Some I have
seen have tags a 2~3 mm wide, which will not fit in the PCB. Others have 3
terminals, which stops you putting it in the wrong way around, but they
will not fit properly on the PCB.

In applications like the 3457A, when the SRAM needs to be kept alive when
power is off, I wish HP would have put two batteries in holders and diode
-OR'ed them. If they had done that, one could just pull out a battery from
holder A, and put a new one in B. Then when B gets old, put one in A.

My first problem though is finding a suitable battery. Next problem is
changing it without losing the RAM contents, but I don't think that's a big
deal.

The 3.6 V Lithium Thionyl Chloride is very tempting, as it has a higher
capacity than the Lithium-manganese dioxide and they have a very low
self-discharge (1%/year). I'm just not overly happy about fitting a higher
voltage battery than it is supposed to have, but phyysically it fits, and I
can get one easy enough from Farnell in the UK.

Dr. David Kirkby Ph.D CEng MIET
Kirkby Microwave Ltd
Registered office: Stokes Hall Lodge, Burnham Rd, Althorne, Essex, CM3 6DT,
UK.
Registered in England and Wales, company number 08914892.
http://www.kirkbymicrowave.co.uk/
Tel: 07910 441670 / +44 7910 441670 (0900 to 2100 GMT only please)
___
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

Re: [volt-nuts] Wanted - UK source of a replacement battery (type LX 1634) for HP 3457A 6.5 digit multimeter

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 24 January 2016 at 22:46, Poul-Henning Kamp  wrote:

> 
> In message 

Re: [volt-nuts] Low-cost voltage reference questions

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 25 Nov 2015 11:18, "Charles Steinmetz"  wrote:
>

> I'm curious why you think the AD587/586 are better than other
hermetically packaged references with better drift and noise specifications
-- in particular,
>
> MAX6350MJA
> AD588KQ
> LTC6655CHLS8
> LTC6655BHLS8
> REF102CM
>
> (see attached table).

Your table mentions at the bottom the LTZ1000, but you don't have that
device listed in the table.  I assume that is an oversight,  but perhaps it
was intensional.

As regards humidity, I wonder if an reasonable attempt at sealing a package
combined with silica gel inside would give an internal humidity that keeps
fairly stable.

I recall seeing a mix of chemicals on eBay that were a calibration standard
for humidity.

I assume that if one got some hermetically sealed feedthrough caps, it
would not be hard to put a PCB inside a tinplate box that's soldered along
each edge to form a hermetically sealed container. Then one would have a
sealed environment. I can imagine it would be desirable to flush out all
solder fumes before making a final seal. Maybe the flux residuals that I
expect outgas over time would cause more problems than it solves.

Note that I have never worked on anything requiring such sealing,  so I
would not be surprised if someone who has worked on such products would
laugh at my suggestions!

I note that Schott appear to produce hermetically sealed enclosures.

I would have thought it practical to build electronics at home where
changes of humidity over time could be virtually eliminated. But I have no
experience in this subject.

Dave.
___
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

Re: [volt-nuts] Low-cost voltage reference questions

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 29 November 2015 at 10:53, Charles Steinmetz 
wrote:

Dave wrote:
>
> As regards humidity, I wonder if an reasonable attempt at sealing a package
>> combined with silica gel inside would give an internal humidity that keeps
>> fairly stable.
>>
>
> That is exactly what I do.  I typically package references in small, cast
> aluminum boxes, and include as large a dessicant packet as will fit in the
> unused space.  Without any special precautions as to sealing, I have never
> seen one of the dessicant packs more than slightly used, even after a
> decade or more and even if there was a hole in the box wall to allow for a
> potentiometer adjustment.  With precautions (using a gasket or sealing the
> seam with RTV after final testing, and sealing any adjustment holes), I
> think you'd be good for a lifetime.
>
> Best regards,
>
> Charles


Are you, or anyone else, aware of any reasons silica gel should not be used
in electronic enclosures?

A friend and I were thinking of developing antennas, which would be used
outside, but enclosed in a fibreglass or similar tube.  I suggested
flushing the antenna with nitrogen, then putting silica gel inside.

He was of the opinion that silica gel was not a good idea. Instead he
reckoned on pressuring the inside with nitrogen above ambient pressure,
and having gas-tight seals would be better. I'm personally of the opinion
that's a bit over the top, as then you need valves to get the nitrogen in.
His idea stuck me as a bit of a sledgehammer to crack a walnut, but he has
better mechanical engineering skills than me.

The difference with the antennas compared to a voltage standard is antennas
would be used in a more hostile environment than a laboratory. So perhaps
whats reasonable in a lab, is not so sensible for an antenna exposed to
wind, rain, ice etc.

Dave
___
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

Re: [volt-nuts] Making a Reference IC

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 13 Sep 2015 09:15, "M K"  wrote:
> There has been some of those references available second hand from ebay,
mostly pulled, but some may be counterfeit, so look for sellers with
pictures showing it as old..

Several sellers have more than 1, but with one photo, so you would have a
hard time arguing that your board is a fake just because it looks newer
than the photo. I believe it is standard practice to photograph a genuine
article but to ship a fake.

In any case, it is probably possible to make a board look older.

A used 3458A fetches several thousand USD, so I find it hard to believe
that many would be broken for parts. But even if there is a reason 3458As
are being broken up, why are other parts not showing up as often as  the
voltage references?

I just looked on ebay for "3458A board" There are 10, of which 6 are the
voltage reference and the other 4 being various other 3458A boards.
Looking for "3458A PCB" changes it to 6 references and 2 two other PCBs. It
seems a bit suspicious to me that the one board that has wider usage than
the others is available in roughly 2~3 times the quantity of all other
boards put together.

We why don't we see 3458A front panels, power supplies etc,  showing up
much - why all the voltage references?

The fact that there seems to be a market for 3458A reference boards
suggests to me that there would be a market for a voltage reference board
based on the same chip, but designed as a stand alone board.

I can think of a few improvements over a 3458A board.

1) Option to run from batteries to keep it as stable as possible when there
are power failures.

It should also make it possible to ship a board to another volt-nut,
keeping it powered in transit.

I don't know the power consumption of the reference,  and I am aware that
there are some issues shipping batteries,  but these seem much more relaxed
if the battery is inside equipment.

2) Option to run chip at a lower temperature than in a 3458A, as some have
claimed is better.

3) Temperature sensor that recorded min and max temperatures during
shipping.

4) Ability to read time board has been powered on.

I for one would buy such a board, if someone produced one, either as a
blank PCB or populated with components & adjusted. Specialist components
would be more readily available is there was a number wanted.

Dave
___
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

Re: [volt-nuts] Anyone know how to make stable inductors?

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 20 August 2015 at 02:38, Todd Micallef <tmical...@gmail.com> wrote:

> Here is a DIY guide to making some lab standards. It is detailed with some
> component values.
>
>
> http://nopr.niscair.res.in/bitstream/123456789/4848/1/JSIR%2065%286%29%20510-513.pdf
>


As I wrote before, I think this is of dubious use, as you are not making an
inductor, but just making the meter indicate there's a low Q inductor, by
using the 4-wires in an incorre

>
> On Wed, Aug 19, 2015 at 8:48 PM, Dave M <dgmin...@mediacombb.net> wrote:
>
> > Here's a paragraph from IETLab's web site on how their inductance
> > standards are made:
> >
> > "Each standard inductor is a uniformly wound toroid on a ceramic core. It
> > has a negligible external magnetic field and hence essentially no pickup
> > from external fields. The inductor is resiliently supported in a mixture
> of
> > ground cork and silica gel, after which the whole assembly is cast with a
> > poƫting compound into a cubical aluminum case."
> >
> > Sounds like their objective is to isolate the winding from as many
> > external influences as possible.  Of course, the same couild be said of
> any
> > physical or electrical standard.
> >
> > Cheers,
> > Dave M
> >
> >
> >
> >
> > Dr. David Kirkby (Kirkby Microwave Ltd) wrote:
> >
> >> I was looking to make some inductors that I can use as a sanity check
> >> for
> >> my HP 4284A LCR meter. I don't too much care what their values are,
> >> but I want them to be stable with time. Any suggestions about the
> >> best way to
> >> make or buy them? I'd like values in the range of 1 nH to 100 mH.
> >>
> >> The LCR meter has 4 terminal Kelvin connections, with 4 x BNC sockets
> >> on a 22 mm pitch.
> >>
> >> The meter is at Keysight at the moment being calibrated, along with a
> >> free software upgrade they are kindly providing. So I'd like to
> >> measure some inductors when it comes back, and track their values
> >> over time, to see if the meter is drifting.
> >>
> >> The meter covers 20 Hz to 1 MHz, and has a basic uncertainty of
> >> 0.05%, so ideally I'd like to keep inductor changes to less than
> >> 0.005% over a year, so the inductor is an order of magnitude better
> >> than the meter. Maybe that is not practical. As I say, the absolute
> >> value is not important, since I only want a comparison.
> >>
> >> The calibration costs on this meter are not too bad (£207 GBP), but
> >> the calibration interval is 6 months, which is a bit annoying. I'd
> >> rather not
> >> be sending it off every 6 months if I can satisfy to myself it has not
> >> drifted too much. Luckily I don't need to satisfy anyone else.
> >>
> >> Dr. David Kirkby Ph.D CEng MIET
> >> Kirkby Microwave Ltd
> >> Registered office: Stokes Hall Lodge, Burnham Rd, Althorne, Essex,
> >> CM3 6DT, UK.
> >> Registered in England and Wales, company number 08914892.
> >> http://www.kirkbymicrowave.co.uk/
> >> Tel: 07910 441670 / +44 7910 441670 (0900 to 2100 GMT only please)
> >>
> >
> >
> > ___
> > volt-nuts mailing list -- volt-nuts@febo.com
> > To unsubscribe, go to
> > https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
> > and follow the instructions there.
> >
> ___
> volt-nuts mailing list -- volt-nuts@febo.com
> To unsubscribe, go to
> https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
> and follow the instructions there.
>
___
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

[volt-nuts] Could you fall an HP 4-wire LCR meter into thinking you have a negative resistor?

[Dr. David Kirkby (Kirkby Microwave Ltd)]

I just sent an email by mistake, failing to finish it before hitting
"send".

The recent discussion about creating inductor standards from a capacitor
and two resistors got me thinking. I suspect if you connected up an HP (or
similar) LCR meter in a way not intended, you could make it appear you have
made a negative resistor. I've not tried it, and some care would be needed,
as it has the potential to damage a meter if one did not use a bit of
common sense.

If you connect the current wires (Lcur and Hcur) to the primary of a
transformer, and measure the voltage at the secondary with Lpot and Hpot,
then one could probably get the meter to indicate a negative resistance. If
the wires to the secondary are are of  the correct phase (just revese them
if not), then the voltage measured on the meter would be out of 180 degrees
out of phase with the current injected. So one could appear to make a
negative resistor. Of course it is not really a negative resistor, and if
measured on a normal multimeter would would just measure the DC resistance
of the transformer.

One could need a bit of care to make sure the meter is not damaged, as one
has the possibility to develop a high voltage on the secondary of the
transformer.

Of course such a negative resistor would have no practical use, but I see
it an obvious extension of making inductors out of capacitors. Unlike the
synthesized inductor, this should be indicate something fairly close to a
pure negative resistor, rather than a very low Q inductor.

Dave
___
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

Re: [volt-nuts] Anyone know how to make stable inductors?

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 20 August 2015 at 02:38, Todd Micallef tmical...@gmail.com wrote:

 Here is a DIY guide to making some lab standards. It is detailed with some
 component values.


 http://nopr.niscair.res.in/bitstream/123456789/4848/1/JSIR%2065%286%29%20510-513.pdf



If this was April the first, I would be convinced that paper was an April
Fools Joke!

I can't imagine how you can make high Q (low loss) inductors, by using a
capacitor and two resistors. It just makes no sense to me, but I will read
the maths later. The mere fact there is resistance makes me think it must
be lossy, so low Q. Also the equations seems to come out with convenient
numbers - R in Ohms, C in pF and H in Henries.

But if the paper is real, it is very close to what I want, although it
still leaves the position of finding stable capacitors. I thought inductors
would be easier than capacitors, but maybe not.

Dave
___
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

[volt-nuts] Anyone know how to make stable inductors?

[Dr. David Kirkby (Kirkby Microwave Ltd)]

I was looking to make some inductors that I can use as a sanity check for
my HP 4284A LCR meter. I don't too much care what their values are, but I
want them to be stable with time. Any suggestions about the best way to
make or buy them? I'd like values in the range of 1 nH to 100 mH.

The LCR meter has 4 terminal Kelvin connections, with 4 x BNC sockets on a
22 mm pitch.

The meter is at Keysight at the moment being calibrated, along with a free
software upgrade they are kindly providing. So I'd like to measure some
inductors when it comes back, and track their values over time, to see if
the meter is drifting.

The meter covers 20 Hz to 1 MHz, and has a basic uncertainty of 0.05%, so
ideally I'd like to keep inductor changes to less than 0.005% over a year,
so the inductor is an order of magnitude better than the meter. Maybe that
is not practical. As I say, the absolute value is not important, since I
only want a comparison.

The calibration costs on this meter are not too bad (£207 GBP), but the
calibration interval is 6 months, which is a bit annoying. I'd rather not
be sending it off every 6 months if I can satisfy to myself it has not
drifted too much. Luckily I don't need to satisfy anyone else.

Dr. David Kirkby Ph.D CEng MIET
Kirkby Microwave Ltd
Registered office: Stokes Hall Lodge, Burnham Rd, Althorne, Essex, CM3 6DT,
UK.
Registered in England and Wales, company number 08914892.
http://www.kirkbymicrowave.co.uk/
Tel: 07910 441670 / +44 7910 441670 (0900 to 2100 GMT only please)
___
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

[volt-nuts] Stabilising resistors

[Dr. David Kirkby (Kirkby Microwave Ltd)]

I have bought some resistors of 0.1, 1.0, 10, 100, 1k, 10k  100k Ohms.
These are in little boxes with 4 BNC connectors spaced 22 mm apart.

This sort of thing

http://m.ebay.co.uk/itm/231460477406

although I paid a *lot* less.

They are designed for use verifying the performance of LCR meters. I don't
know what the uncertainty of *impedance* on these are, but they are
probably optimised for use to 1 or more MHz rather than DC resistance
standards. At least one I bought is supplied with a 120 MHz LCR meter, but
the others are possibly designed for a lower frequency. Getting
specifications on these is not easy.

My HP 4284A LCR meter is at Keysight being calibrated.  My aim is to use
these resistors as a way of tracking drift in the meter which would
indicate it needs calibration.  The basic uncertainty of the HP 4284A meter
is 0.05%, although it is higher at very low and very high impedances.

Is there realistically anything I can do to stabilise these resistors? I
don't want to go to the expense of adding Peltier temperature controllers
to them.

I suspect the fact that they are several years old means that they are as
stable as they are going to be, but I just wanted to check if there is any
improvement that I could make. I expect thermally cycling these in an oven
and fridge would do more harm than good,  but perhaps I am wrong.

I do have a 3457A 6.5 digit multimeter which has not been in a calibration
lab for at least 15 years, although I have measured some 0.005% resistors
as a check for gross errors.  It would be worth tracking these HP resistors
with that too.

It is not worth paying commercial rates for calibration of the resistors as
getting the LCR meter calibrated at Keysight is not that expensive (£207
GBP). Keysight also agreed to provide me a software option 006 (support for
2 m  4 m cables), so getting the meter calibrated was especially good
value.

Dave
___
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

[volt-nuts] Keysight seminar of possible interest to those in the UK

[Dr. David Kirkby (Kirkby Microwave Ltd)]

This might interest those with an interest in metrology in the UK. It
is run by Keysight on the 16th and 18th June

http://www.keysight.com/main/eventDetail.jspx?cc=USlc=engckey=2553856nid=-33166.920244.08id=2553856cmpid=1-6830540895

The annoying this is Keysight are running something else that
interests me on the 17th June

http://www.keysight.com/main/eventDetail.jspx?cc=USlc=engckey=2548118nid=-33166.920244.08id=2548118cmpid=1-6830540895

with the two locations more than 200 miles apart. It makes it just
about impractical to attend both


Dr. David Kirkby Ph.D CEng MIET
Kirkby Microwave Ltd
Registered office: Stokes Hall Lodge, Burnham Rd, Althorne, Essex, CM3 6DT, UK.
Registered in England and Wales, company number 08914892.
http://www.kirkbymicrowave.co.uk/
Tel: 07910 441670 / +44 7910 441670 (0900 to 2100 GMT only please)
___
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

[volt-nuts] Seminar: Fundamentals of Low Current and Ultra-High Resistance Measurement

[Dr. David Kirkby (Kirkby Microwave Ltd)]

Google that and you should find a seminar sponsored by Keysight,
scheduled for Tuesday, April 14, 2015 1:00pm ET / 10:00am PT (I'll
convert to GMT later)

Trouble is, it is streamed in a Windows format.

Dr. David Kirkby Ph.D CEng MIET
Kirkby Microwave Ltd
Registered office: Stokes Hall Lodge, Burnham Rd, Althorne, Essex, CM3 6DT, UK.
Registered in England and Wales, company number 08914892.
http://www.kirkbymicrowave.co.uk/
Tel: 07910 441670 / +44 7910 441670 (0900 to 2100 GMT only please)
___
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

[volt-nuts] Checking an LCR meter

[Dr. David Kirkby (Kirkby Microwave Ltd)]

I have bought an HP 4284A precision LCR meter. This is an old model with a
basic accuracy of 0.05% and covers 20 Hz to 1 MHz.

Converting the specifications into determining the uncertainty of a
measurement is nontrivial, but I think it reasonable to assume the
uncertainty will always be 0.05%.

Surprisingly the current precision LCR meter from Kesight, the E4980A (20
Hz to 2 MHz) offers the same basic accuracy. So while fairly old, the 4284A
doesn't seem to be miles behind the current crop  LCR meters from the top
manufacturers.

The recommended calibration period on the 4284A is 6 months, which would
get rather expensive - on the current E4980A the calibration period is a
more respectable 12 months.

I am looking for suggestions on how I can get reasonable confidence in
the instrument at reasonable cost, without returning it to Keysight every
6 months.

I have a 3457A DVM, but mot much else in the way of precision low frequency
equipment.

It has 4 BNC connectors for Kelvin probes.

I suspect that getting precision resistors and keeping them for a house
standard might be worthwhile,  but are looking for suggestions on the best
approach.

I will send it to Keysight once when it arrives to ensure that there are no
faults on it, but I don't currently feel I can justify getting it
calibrated every 6 months.

Maybe I can make some stable standards, then measure them soon after the
LCR meter calibrated been calibrated and periodically measure their values.
Any suggestions about how to approach that?

Dave
___
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

Re: [volt-nuts] 3458A reference boards on ebay

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 30 January 2015 at 12:25, Will willvo...@gmail.com wrote:
 The boards are factory rejects.

I doubt all boards on eBay are in this category. Some are probably
quite genuine, some may be rejects, and it would never surprise me if
some are counterfeit. The problem is, I have no idea what ones are
what.

I don't know what the problems sourcing the parts for making a
reference would be, but if a number of people wanted to make one from
parts, perhaps someone could produce a PCB and people contribute
towards the cost of it. Maybe leave people to get their own reference
chip, as there are different grades of that. But things like the
precision resistors may be easier to buy in a quantity of 10 rather
than 1.

I would certainly not mind buying one if a PCB was available. Even if
it works out costing a bit more than a 3458A reference from eBay, I'd
feel a bit happier.

Dave
___
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

Re: [volt-nuts] 3458A reference boards on ebay

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 27 Jan 2015 09:47, Orin Eman orin.e...@gmail.com wrote:

 There is a seller letting a slow trickle of them out there... they seem to
 be going for about $165.  The current batch of two is around $100, but
will
 probably be bid up.

I am puzzled why there are so many reference boards that are supposed to
come from 3458As on the used market. It makes me wonder if they are
genuine.

One seller,  with the two high stability reference boards at $750, claims
that they come from working and recently calibrated 3458As. Why would
anyone wreck a working and recently calibrated 3458A?

It is not beyond the bounds of possibility that a 3458A might be worth more
in parts than as a complete unit. I know this is true for some HP items,
but I doubt that is the case with a 3458A.

Another seller,  who has them at $395 or offer, has sold 17 and has 11
left.

Although expensive,  having two and monitoring the difference between them
would probably allow their stability to be measured with a DVM of modest
specification.

There are lots of counterfeit components around,  and I fear that it could
be some of these boards could fall into that category.  This makes the
building a board from new components more attractive.  In the short term it
is likely to be less stable than an old reference,  but at least one would
know the history of it. If the components were sourced from reliable
sources, it would get around the  potential counterfeit problem.

Dave.
___
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

Re: [volt-nuts] plastic caps on 3458A reference board

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 28 January 2015 at 18:56, Charles Steinmetz csteinm...@yandex.com wrote:

 The problem is that an LTZ1000 (or LM399) runs hot enough that most plastics
 you find lying around won't stand up to it for very long (some of them melt
 almost immediately when you power it up).  This is true even of
 polycarbonate, which is one of the most durable common plastics, and is why
 the original caps were made from polysulfone.

 Unfortunately, it also means that replacements may be hard to make by 3D
 printing, since the process depends on melting the base material.

 Best regards,

 Charles

Is there any reason this cap is not made of metal? If its purpose is
to restrict airflow by convection, metal will do. Copper sheet can
easily be soldered to make something that would restrict airflow and s

If you want thermal insulation, then PTFE rivited to a metal shield
would provide a plastic that will not melt, and the metal would keep
it in place, as its hard to form a box out of PTFE. It is not an easy
material to glue, but nuts/bolts/rivits will work.

Dave
___
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

Re: [volt-nuts] 3458A reference boards on ebay

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 27 January 2015 at 09:16, Orin Eman orin.e...@gmail.com wrote:
 There is a seller letting a slow trickle of them out there... they seem to
 be going for about $165.  The current batch of two is around $100, but will
 probably be bid up.

 I just received one that I won.  Seems to be working fine after a quick
 breadboard lashup.  I'll be making an enclosure for it next.

 A little expensive IMO, but given the trouble getting the precision
 resistors to DIY with the LTZ1000A, probably worth it.

 Orin

Orin,

What do you intend doing with it?

I was thinking about getting one of those, with a view to putting it
in a box with a couple of terminals to have something to compare with
my 6.5 digit 3457A.  But what put me off is a lack of knowledge in
knowing how to convert a 3458A reference board into a boxed unit with
a known output voltage at the terminals. How would I avoid / control
thermal EMFs?

I'd be interested to hear what your plans are for it, and how you
intend tackling those issues.

Do you know what the difference in the reference is between a standard
3458A (8 ppm) and the high stability option 002 (4 ppm) model? I'm
guessing the chips for the option 002 might be the top performing
ones. I wonder if there's any way to tell from your board if it came
from a standard 3458A or a 3458A with option 002.

Dave
___
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

Re: [volt-nuts] Design Spark PCB Design Package

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 5 Jan 2015 15:36, Randy Evans randyevans2...@gmail.com wrote:

 This is indirectly pertinent to the group since I am designing a PCB for
 the HP-419A and Fluke 845A modifications.  Does anyone have any
 experience/comments on the Design Spark PCB design package?  Is is a
viable
 package for hobbyist use?

 thanks,

 Randy Evans

I have not used it.

Have you looked at Kicad? It is used by both professionals and hobbyists,
and being open source, is not reliant on RS to update it.

Now there is a decent open source PCB layout program,  I would not suggest
anyone learn a new proprietary package unless there were very good
reasons,  such as an employer says you must use a particular program.

Dave
___
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

Re: [volt-nuts] The averaging reference

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 20 Dec 2014 21:18, Joel Setton set...@free.fr wrote:

 Jan,

 Thanks for a good summary f the pros/cons. Of course the LTZ1000 is much
closer to the current state of the art, but the REF102 is far easier to use
and to calibrate. I'm definitely not shooting for sub-ppm performance, if I
can build anything that stays within (say) 20 ppm long-term, that would be
more than adequate as a home standard.

 One thing I don't like about the LM199 and LTZ1000 is that although they
are stable, they are sold uncalibrated. As a result, building a 10-V
reference with either of them would require at least two very stable
resistors, one of which must be selected within a range of several percent
to get an accurate 10V output.

I suspect if you built something very stable using an LTZ1000, it would be
possible to get one or more volt-nut with a 3458A or similar to measure it
for you.
You could even average the result from several volt nuts.

Dave.
___
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

Re: [volt-nuts] The averaging reference

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 19 Dec 2014 19:30, Jan Fredriksson j...@41hz.com wrote:

 It's no coincidence that virtually all 8.5 digit DMMs use the LTZ1000.
 It's in a class of it's own.

What do the 8.5 digit meters use if they don't use the LTZ1000?

Dave.
___
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

Re: [volt-nuts] The averaging reference

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 18 Dec 2014 19:06, Poul-Henning Kamp p...@phk.freebsd.dk wrote:

 
 In message 5492f59e.8060...@free.fr, Joel Setton writes:

 In my search for the Perfect Volt, I'm thinking about building a
 reference voltage generator which would average the voltages generated

 If you want to do it right, you should average all sorts of
 different (but obviously: good) chips, possibly assigning them
 different weight depending on their qualities.

I was aware of  three 8.5 digit multimeters

* Keysight 3458A
* Fluke 8508A
* Keithley 2002.

But

http://www.eevblog.com/forum/testgear/8-5-digit-dmm/

lists several others - some from manufacturers I have never heard of.

I would assume that they all use a state of the art voltage references. I
wonder if they all use the same method?  If not, perhaps averaging those
would be one approach.

How would you average them? Assuming they are supposed to be the same
voltage, would it be OK to tie N output together with N resistors? Use low
value resistors on the references you trust most, and higher values on
those you trust least.

Dave
___
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

Re: [volt-nuts] Buying HP-3458A

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 6 Jul 2014 07:12, John Phillips john.philli...@gmail.com wrote:

 ​They do really offer that service as​ long as you send them a complete
 meter... No missing parts. Well they will take a few missing screws and
 such.

There is also the possibility someone has tried repairing it, but done so
badly.

I assume that there has been some design changes over the years, so not all
boards are identical.  Agilent would probably decline to fix a unit made
from parts from a mixture of revisions.

Buying one and hoping to get it repaired for a fixed fee seems a bit risky
to me.

Dave

My experience with them is they charge the same no mater what need to
 be fixed. Not sure what the price is, there prices are country dependent.
I
 thought it was a little more than $2200 last I checked.


 On Sat, Jul 5, 2014 at 4:08 PM, Randy Evans randyevans2...@gmail.com
 wrote:

  I am in the market for a used HP-3458A and, in researching past
messages, I
  came across an interesting question:
 
  *Chris Erickson* ericksonc2 at comcast.net
  volt-nuts%
 
40febo.com?Subject=Re%3A%20%5Bvolt-nuts%5D%203458A%20questionsIn-Reply-To=%3C001b01cc7960%24a15d2840%24e41778c0%24%40net%3E
  
  *Thu Sep 22 19:48:41 UTC 2011*
 
  If Agilent will fix everything, bring it up to specs, and calibrate it
no
 
  matter what's wrong with it for $2200, then why would I spend
$5000-6000 or
 
  more for one that is in good shape - even if calibrated? Just grab the
  first
 
  bargain that comes along for $1500-3000, send it straight to Agilent
and be
 
  money ahead. Seems the better course of action to me if that price is
 
  accurate - do they really offer this service?
 
 
 
 
  I could not find an answer to this question but it does beg the
question.
   Does nayone have an answer as to why not buy the cheapest unit and
send it
  in for repair?
 
 
  Thanks,
 
 
  Randy Evans
  ___
  volt-nuts mailing list -- volt-nuts@febo.com
  To unsubscribe, go to
  https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
  and follow the instructions there.
 



 --
 John Phillips
 ___
 volt-nuts mailing list -- volt-nuts@febo.com
 To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
 and follow the instructions there.
___
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

Re: [volt-nuts] Batch of old reference zeners

[Dr. David Kirkby]

On 9 Mar 2014 23:39, Jan Fredriksson j...@41hz.com wrote:

 I have a batch of voltage references ICs on the shelf, several thousand of
 each type. They all have date codes of around 1983, ie 30 years old. It
 would be great to have some drift data on them.

Since you have so many, it would be interesting if you built up some
references, measured their stability, then shipped a random sample around
the world - perhaps to two or three time-nuts on different continents. Then
see if the transport actually has any effect on them.

The discussions about the Fluke being shipped powered up made me think of
this one.

Of course shipping them powered up could be an additional interesting
experiment, but as I wrote before, there are issues with that, although
perhaps if the current consumption was low enough, the size of the battery
needed would be incredibly small, and one could probably chose a type for
which there is no strict regulations about carrying them.

Dave
___
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

Re: [volt-nuts] A Fluke 732A: Return it or keep it?

[Dr. David Kirkby]

On 8 Mar 2014 05:57, Charles Steinmetz csteinm...@yandex.com wrote:

 Michael wrote:

 The battery is big concern to me. When I called Fluke, one of the rep
said it should be shipped to them hot Because 732A's battery life is very
limited, it should be shipped using Morning Service. I was going to call
FedEx if they have 12 hours service. And I belive most cal lab require the
732A to be delivered hot. The manual says so.


 No matter what you do, short of hand-delivering it if you live close
enough, the internal battery does not have enough charge to reliably ship
it, even overnight.  You will need to build or buy a shipping container
that has an auxiliary battery.  Fluke sells external battery packs for
$375, or you can make your own.

Be careful about shipping issues on high energy batteries. Depending on the
capacity, they may need to be declared as dangerous goods. I recently
needed to ship a Lithium Ion battery about the size of a laptop battery.
The courier I normally use (Interparcel, who subcontract to UPS, Fedex or
whoever one chooses), wont handle batteries. Going directly to Fedex,
without having a contract, cost a fortune, although they would carry the
battery.

The fact a battery is external to the equipment makes it even more tricky
to ship, since I guess there is more chance of a short developing in such a
case.

Dave
___
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

Re: [volt-nuts] Economical Standard Calibration

[Dr. David Kirkby]

On 8 March 2014 21:44, Dallas Smith dosm...@outlook.com wrote:
 Hi nuts,
 This is my first post. The knowledge from contributors is amazing.

 Was wondering where one could economically get our voltage standards
 calibrated
 to some traceable standard since Joe Gellar suspended  operations for his
 SVR-T?

 voltagestandard.com doesn't sell a 10v references and two of his 5v
 Vref5-002 are costly.

 Dallas

It would be worth stating what meter you have. Clearly what is going
to be useful for a 3.5 digit meter, will not be for an 8.5 digit one.

Dave
___
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

Re: [volt-nuts] Extender Card for Guildline 9975

[Dr. David Kirkby]

On 18 Jan 2014 14:38, Joe Hobart n...@npgcable.com wrote:

 Does anyone have or know where I can buy or borrow a 12/24 contact
 extender card
 for the Guildline 9975?  I have a single sided extender, but the signal
 demodulator board requires a double sided extender.  Of course, it is this
 card
 that needs additional testing and possible repair.

 Thank you,
 Joe Hobart
 Flagstaff, Arizona
 ___
 volt-nuts mailing list -- volt-nuts@febo.com
 To unsubscribe, go to
 https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
 and follow the instructions there.

___
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.

Re: [volt-nuts] Agilent calibration - certificate for a vector network analyzer (VNA)

[Dr. David Kirkby]

On 24 August 2013 18:55, Joseph Gray jg...@zianet.com wrote:
 David,

Hi Joseph

 That is quite a difference between the two certificates. The Techmaster one
 doesn't tell you anything about what they actualy measured, or the
 uncertainties. You have to trust that they know what they are doing and
 that they actually did it.

I think Techmaster certificates are useful to T+M dealers, as they can
sell things for a higher price. Their certaificates are also useful to
end users that just need a certificate to satisfy some institute or
body. But I don't believe it would satisfy a competent engineer who
really wanted to know if the instrument was working properly. A
competent enginner would not be too conviced.

When an Agilent VNA calibration expert (Ken Wong) wrote on the Agilent
VNA forum that I will be very skeptical when a VNA calibration
service does not include a cal kit and verification kit. and that
Techmaster cal certificate did not use a verification kit, one has to
be sceptical.

The fact Techmaster also issued a cal certificate for a calibration
kit makes me suspicious too. Apparently you need access to primary
standards to verify they are in spec.

There is something else interesting on that Techmaster certificate.
Note it says option 010 added. That is a software option (enables a
Inverse Fourier transform to convert frequency domain data to time
domain). It is no longer sold by Agilent. I do wonder if that was
legally added. Buying that option for a new VNA costs several thousand
dollars, but the 8720D was last made in around 1999, and has been
unsupported since 2004. I suspect these cal labs are useful for things
like getting software options added! Agilent will certainly not sell
the option.

 With the Agilent certificate, there is data to
 give you confidence that things were done properly.

Yes. Note the Agilent calibration is not acreditated by anyone. I
could have had an acredited calibration, but I did not want to pay the
extra 50% or so. From what I understand, the VNA would be calibrated
in exactly the same way. But it costs Agilent money to get acredited
for the calibration, so they pass that cost onto those that want it
acredited.

For me personally, I trust Agilent know how to calibrate VNAs. There
is going to be more VNA expertese in Agilent than arguably any other
institution.

 Thanks for posting those. It was educational.

I'm glad you found it useful.

 Joe Gray
 W5JG

Dave, G8WRB
___
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.