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

[acbern]

understand, it is maybe different here in Germany then, there are a number of 
labs with pretty low uncertainties who also support old gear adjustments.
on the other hand, you have to know who you are working with for what gear. 
Otherwise you can have unpleasant surprises.
in your case, if you have no nobody calibrating your meter with a specified 
uncertainty, maybe an option is to build your own decade of resistances and use 
a precisiion high voltage source (calibrator) and a 3458A as current meter. 
that brings you to say 10nA/100Gohms. if thats sufficient.



> Gesendet: Donnerstag, 19. April 2018 um 18:41 Uhr
> Von: "Dr. David Kirkby" 
> An: "Discussion of precise voltage measurement" 
> Betreff: Re: [volt-nuts] Would you be concerned if the manufacturer does not 
> have an uncertainty budget, so can't provide uncertainties in a calibration?
>
> 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
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Re: [volt-nuts] Would you be concerned if the manufacturer does not have an uncertainty budget, so can't provide uncertainties in a calibration?

[acbern]

-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.






> Gesendet: Donnerstag, 19. April 2018 um 14:08 Uhr
> Von: "Dr. David Kirkby" 
> An: "Discussion of precise voltage measurement" 
> Betreff: [volt-nuts] Would you be concerned if the manufacturer does not have 
> an uncertainty budget, so can't provide uncertainties in a calibration?
>
> 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
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Re: [volt-nuts] 3458A drift checking question

[acbern]

the manual defines a 4 hours warmup time. after tat the meter is supposed to be 
within spec. 
then the note 18 test can be started (ACAL and reading the cal constant).
then it should be left on for a couple of days before a new acal is done, 
ideally as long as the note 18 specifies (7days iirc) , however if you see 
there is no drift (against a known good 732A e.g.), then it might be shortened. 
my experience is, if an AD board has a drift issue, it drifts quite a bid in 
short time in most of the cases, have seen 10+ ppm a day.
also, note 18 covers two drift issues, AD and REF board related drift. do not 
confuse.




> Gesendet: Mittwoch, 10. Januar 2018 um 12:34 Uhr
> Von: "David C. Partridge" 
> An: "'Discussion of precise voltage measurement'" 
> Betreff: [volt-nuts] 3458A drift checking question
>
> How long does the meter need to have been powered on before it makes any
> sense to perform the Service Note 18 drift test?
> 
> Thanks
> Dave
> 
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Re: [volt-nuts] Drifting 3458As

[acbern]

If you are confident that the 732A is stable to 0.1ppm then just run an acal 
afer a wek, and determnine what has driifted. Your A/D board, as can be seen 
with a drifty cal constant, or, els the A9 ref.
Dont do a checl everyday. this hides information. 



> Gesendet: Freitag, 01. Dezember 2017 um 19:49 Uhr
> Von: "Randy Evans" 
> An: "Discussion of precise voltage measurement" 
> Betreff: Re: [volt-nuts] Drifting 3458As
>
> I am running the ACAL to check cal constant drift over several times a day
> and over a 7 day period (per SN18).  The varying times of the day are to
> see how temperature sensitivity affects the cal constant drift since the
> room temperature is not constant through the day but is relatively constant
> at the same time of day each day; i.e., the furnace is off during the night
> so mornings are about 5 degrees C cooler than the afternoon.  Even after
> ACAL, I am seeing up to an absolute difference of 3.5 uV on the 732A
> voltage reading between the HP and Agilent 3458As, depending on the time of
> day.  I suspect the A9 board in the Agilent is the reason since the HP
> 3458A reads much closer to the 732A value than the Agilent 3458A over
> temperature.  Based on long term comparisons with other 732As and a 732B, I
> am confident the 732A is stable within 0.1uV.
> 
> I am using an ebay A9 board in the Agilent 3458A for the current testing
> since I suspect the original A9 board in the Agilent 3458A.  I am
> separately testing the original A9 board since I am not completely
> confident in the ebay A9 board.  I do not have enough data to draw a
> conclusion yet about the original A9 board.  My current concern is to see
> if there is agreement that the A9 board is likely the culprit.
> 
> Thanks,
> 
> Randy Evans
> 
> On Fri, Dec 1, 2017 at 1:58 AM,  wrote:
> 
> > What you describe (A9 drift) would be the explanation. However question is
> > how much you see. The A9 should not drift much in the intervals you talk
> > about (days).
> > Also, you should run the ACAL to determine the cal constant not several
> > times a day but with several days inbetween, and then divide by number of
> > days to determin drift
> > Frequent ACAL may not give you good results (random fluctuations such as
> > noise, temp... and their impact during cal gets higher the shorter the time
> > between ACALs)
> >
> >
> >
> > > Gesendet: Donnerstag, 30. November 2017 um 07:40 Uhr
> > > Von: "Randy Evans" 
> > > An: "Discussion of precise voltage measurement" 
> > > Betreff: [volt-nuts] Drifting 3458As
> > >
> > > I have been testing two 3458As against a known good Fluke 732A. Each
> > 3458A
> > > was calibrated for DCV before the start of the measurements so they both
> > > started at the same point.   I have been running a series of tests
> > > consisting of measuring the Cal Constant as detailed in Service Note 18
> > for
> > > each meter several times a day (to calculate the drift per the procedure
> > in
> > > SN 18).  I also measure the 732A voltage in each meter each time using
> > NLPC
> > > 100 and NRDGS 100 and then recording the STDEV, MEAN, MAX, and MIN
> > values.
> > > What I have observed is that the Cal Constant is acceptably low but the
> > > MEAN value per measurement  is drifting up in one meter and drifting down
> > > in the other.   The unit drifting down has a new A3 board installed and
> > the
> > > unit drifting upward is an Agilent 3458A only a few years old so would
> > not
> > > be expected to have a drifting A3 board.  It was only calibrated 1 time
> > per
> > > the internal REV number, so would have likely been re-calibrated if the
> > A3
> > > board was replaced.
> > >
> > >
> > >  My question is what is the likely cause of the drift in the MEAN voltage
> > > reading if the Cal Constant value is relatively constant?  SN 18 says the
> > > drift rate of the Cal Constant is an indication of drift in the A3 AD
> > > board, but I believe it assumes the A9 voltage ref board has a constant
> > > value over time.  If this is not true (e;g., the voltage ref is
> > drifting),
> > > I think this would explain the drift in the voltage reading even though
> > the
> > > Cal Constant is relatively constant.  Any opinions on this?
> > >
> > >
> > > Thanks,
> > >
> > >
> > > Randy Evans
> > > ___
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> > mailman/listinfo/volt-nuts
> > > and follow the instructions there.
> > >
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Re: [volt-nuts] Drifting 3458As

[acbern]

What you describe (A9 drift) would be the explanation. However question is how 
much you see. The A9 should not drift much in the intervals you talk about 
(days).
Also, you should run the ACAL to determine the cal constant not several times a 
day but with several days inbetween, and then divide by number of days to 
determin drift
Frequent ACAL may not give you good results (random fluctuations such as noise, 
temp... and their impact during cal gets higher the shorter the time between 
ACALs)



> Gesendet: Donnerstag, 30. November 2017 um 07:40 Uhr
> Von: "Randy Evans" 
> An: "Discussion of precise voltage measurement" 
> Betreff: [volt-nuts] Drifting 3458As
>
> I have been testing two 3458As against a known good Fluke 732A. Each 3458A
> was calibrated for DCV before the start of the measurements so they both
> started at the same point.   I have been running a series of tests
> consisting of measuring the Cal Constant as detailed in Service Note 18 for
> each meter several times a day (to calculate the drift per the procedure in
> SN 18).  I also measure the 732A voltage in each meter each time using NLPC
> 100 and NRDGS 100 and then recording the STDEV, MEAN, MAX, and MIN values.
> What I have observed is that the Cal Constant is acceptably low but the
> MEAN value per measurement  is drifting up in one meter and drifting down
> in the other.   The unit drifting down has a new A3 board installed and the
> unit drifting upward is an Agilent 3458A only a few years old so would not
> be expected to have a drifting A3 board.  It was only calibrated 1 time per
> the internal REV number, so would have likely been re-calibrated if the A3
> board was replaced.
> 
> 
>  My question is what is the likely cause of the drift in the MEAN voltage
> reading if the Cal Constant value is relatively constant?  SN 18 says the
> drift rate of the Cal Constant is an indication of drift in the A3 AD
> board, but I believe it assumes the A9 voltage ref board has a constant
> value over time.  If this is not true (e;g., the voltage ref is drifting),
> I think this would explain the drift in the voltage reading even though the
> Cal Constant is relatively constant.  Any opinions on this?
> 
> 
> Thanks,
> 
> 
> Randy Evans
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Re: [volt-nuts] Get 10K resistor calibrated in UK

[acbern]

mine, since it was built in 1977, has drifted upwards by 1.6ppm.
There is also a picture showing druft data of several SR104s on eevblog, but 
dont have the link handy.




> Gesendet: Mittwoch, 29. November 2017 um 15:25 Uhr
> Von: "Electronics and Books via volt-nuts" 
> An: "Discussion of precise voltage measurement" 
> Betreff: Re: [volt-nuts] Get 10K resistor calibrated in UK
>
> can anyone tell me howmuch a SR104 10k resistor drift
> 
> Met vriendelijke groeten
> Regards
> Frans
> 
> electronicsandbo...@yahoo.com
> http://ElectronicsAndBooks.com
> Netherlands
> 
> Discere ne cesses
> 
> 
> On Wed, 11/8/17, David C. Partridge  wrote:
> 
>  Subject: Re: [volt-nuts] Get 10K resistor calibrated in UK
>  To: "'Discussion of precise voltage measurement'" 
>  Date: Wednesday, November 8, 2017, 4:08 PM
>  
>  I guess that depends on your
>  definition of cheap :(  
>  
>  Dave
>  
>  -Original Message-
>  From: volt-nuts [mailto:volt-nuts-boun...@febo.com]
>  On Behalf Of Alan Ambrose
>  Sent: 08 November
>  2017 14:31
>  To: volt-nuts@febo.com
>  Subject: Re: [volt-nuts] Get 10K resistor
>  calibrated in UK
>  
>  NPL i.e.
>  the UK national lab, are also surprising flexible and cheap.
>  Looking at their schedule for '15/'16 (the one I
>  happen to have to hand) they had 10K ohm cal 30-Nov-15 to
>  11-Jan-16 @ £510. They also had voltage cal October and
>  March at ~£420.
>
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Re: [volt-nuts] Best way to measure micro Ohms

[acbern]

The question is what accuracy you need.
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)


> Gesendet: Sonntag, 17. September 2017 um 19:23 Uhr
> Von: "Dr. David Kirkby (Kirkby Microwave Ltd)" 
> 
> An: "Discussion of precise voltage measurement" 
> Betreff: [volt-nuts] Best way to measure micro Ohms
>
> 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.
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Re: [volt-nuts] Fluke 732a concernes

[acbern]

Igor,

I would actually ignore the 1V and 1.018V outputs. You can always determine 
their actual value using your 3458A in transfer mode against the 10V. The 
purpose of a voltage reference is not to be at exactly the nominal value all 
the time (requiring readjustment), but just to be close to nominal with known 
deviation and known drift rates. Working 732As show a very low drift, well 
below spec, provided you do not do much adjustment (never adjust the trimmers). 
Users have seen massive drifts starting when this was done. My 732A e.g. has a 
drift of only about 0.2ppm pa over a couple of years, so pretty good. The drift 
direction may change when you let it cool down, so you dont want to switch it 
off.

cheers



> Gesendet: Dienstag, 29. August 2017 um 07:27 Uhr
> Von: Igor 
> An: "volt-nuts@febo.com" 
> Betreff: [volt-nuts] Fluke 732a concernes
>
> Hello,
> 
> I am Igor and I am new to this forum. I have a Keithley 2002 and 3458A.
> 
> As probably a prerequisite for this list, I recently acquired a Fluke 732a 
> and checking it our now. I do not have any history for the unit and it was 
> shipped to me cold without batteries and with broken battery carrier.
> 
> After a warm up 10V read about 7ppm high and 1.018V read about 13ppm high. 
> This is probably ok for a very old unit like this.  However 1V read 116ppm 
> high! Is this typical? Would it be a sign of internal resistor drift?
> 
> I had to move an internal jumper for 5ppm adjustment and then adjusted 10V 
> and 1.018V to proper value using a calibrated meter. I do not see any way I 
> can adjust 1V output to be even close to spec. Is opening the oven and 
> adjusting resistors an option? Should I just leave it alone and monitor drift?
> 
> When fully warmed up the thermistor measured 3.662KOhm. Is this a typical 
> performance?
> 
> Additionally when inspecting the unit in more details I found a burned PCB 
> patch on A4 Regulator board, right under R12 and R13 resistors in proximity 
> to transistor Q4 and capacitor c8. It is literally burned to black crisp. The 
> resistors themselves appear ok. Maybe they had been changed after the board 
> burned.
> 
> When running the board I get transistor Q4 as hot as 220F, still below its 
> 150C max running temperature. The PCB board and resistors get to 180F. Is 
> this normal, or should I be concerned?
> 
> 
> Thank you very much.
> ___
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Re: [volt-nuts] PCBs with ceramic substrates

[acbern]

well, certain Rogers materials have an even higher surface resistance than 
PTFE, and are the preferred choice in that case.



> Gesendet: Donnerstag, 06. April 2017 um 06:38 Uhr
> Von: "Attila Kinali" 
> An: volt-nuts@febo.com
> Betreff: [volt-nuts] PCBs with ceramic substrates
>
> Moin,
> 
> I recently wondered, why people around voltage metrology hardly
> talk about ceramic substrates (Al2O3, AlN, ...) for PCBs.
> They have surface resistivity that is as high as PTFE, have
> higher thermal conductivity, lower thermal expansion (AlN is
> even pretty close to Si). So, why then does it hardly ever get
> mentioned? Is it the cost of those? Or is there something I am
> missing?
> 
>   Attila Kinali
> 
> -- 
> You know, the very powerful and the very stupid have one thing in common.
> They don't alters their views to fit the facts, they alter the facts to
> fit the views, which can be uncomfortable if you happen to be one of the
> facts that needs altering.  -- The Doctor
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Re: [volt-nuts] Low-cost Josephson Junction Array

[acbern]

About two years ago I started an exercise to determine what it would take to 
build a kind of DIY JJ standard and also looked at certain detail technical 
aspects of designing/building what is reasonable doable. Baseline was 10V DC. 
It was clear that it would not be cheap, and I also looked at this as a 
personal challenge. So here in a nutshell: 
I did talk to a vendor of the JJA, and we finally agreed he would be supporting 
me with supplying a JJA and related waveguide with flange attached. Nothing 
else, to save costs. What would have remained is the 75Ghz RF source (including 
further waveguides with dewar interface and helium block, RF source, 
directional coupler and RF generator. Key is a source with low harmonics, so 
using a trippler and a 26.5GHz generator (locked to a gps-calibrated rubidium 
source) was a potential solution, but it was not clear if that would have been 
sufficienly clean overall, so quite some risk here having to go with another 
solution finally (Gunn...). Also the amplifier portion and transmission of the 
RF signal to the JJA without too much loss is not that simple, as the power 
needed is not that low. Lots of discussions with the vendor. Helium would have 
been obtained in a loaner dewar from a gas manufacturer, I did have a quotation 
at pretty reasonable cost, no need to go with a cryocooler (which ca
 n cause a lot of voltage noise potentialy, killing the DC signal). And some 
driving electronics of course, doable with reasonable effort. While I had some 
equipment such as e.g. the RF generator and reference clock, the shopping list 
was not that short. Also some test gear such as a 75GHz power head and so on 
was also on the shopping list. 
To make a long story short, I ended up with an estimate of 30 to 40 kUSD, with 
about 10k of additional risk, with the majority being the cost of the JJA. 
Quite some expense for an in the end academic exercise, so I finally decided to 
not further pursue this. I need to add that, being an EE, with no experience in 
cryo stuff, I would have got support by a fried who is physicist, otherwise I 
would not even have considered it (you cannot just put the JJA into the 
dewar...). There are some potential ways to cut the costs mentioned, e.g. by 
going with 1V instead, or having access to suitable 75GHz gear, but it is still 
a several 10k exercise.
Overall, at least from my perspective, it was just not worth it. Quite some 
risk and lots of time until it works. So I continue to send my references to a 
good lab with well below 1ppm of uncertainty, and I have an independent cal 
document, even though of course, it would certainly have been a lot of (quite 
expensive) fun.




> Gesendet: Donnerstag, 20. Oktober 2016 um 00:35 Uhr
> Von: "Ken Peek" 
> An: volt-nuts 
> Betreff: Re: [volt-nuts] Low-cost Josephson Junction Array
>
> @Vince:
> 
> Thank you for the link!  Very informative!  There is also a nice video
> showing some of the lab techniques, and some cautions working with
> cryogenic liquids.
> 
> I would also like to explore miniature cryocoolers-- as these might be able
> to support a small lower power array (1V) if it doesn't dissipate too much
> power...
> 
> There is already some progress in this area with a QHR made from graphene
> (at the NPL in the UK).  So, maybe the same cryocooler could be used also
> for the low-cost JJA ?
> 
> Having a 10V (fixed output) JJA and a 12K9 QHR would be the basis to
> calibrate all other electrical standards in a lab.  It would be nice to
> have these sitting in their cryocoolers cranking out volts and ohms
> practically indefinitely (or as long as you want)-- and if one has even a
> rubidium atomic clock, then no external signals or standards of any kind
> would be needed.  Well, that and a triple-point of water cell (which I
> have) for temperature calibrations.
> 
> -Ken
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Re: [volt-nuts] HP 3458A/HFL : looking for information/photos/fw

[acbern]

The value of the HFL is that by spec, it is better. So you can use its improved 
values in your uncertainty budget. If you do an upgrade yourself, you cannot 
rely on that. So you have to characterize your instrument after that. But you 
can as well do that with the standard meter as-is, and probably end up with 
results as good as the HFL, especially if it is a meter that has the VHP101 
resistor installed (ACAL does the rest). 



> Gesendet: Mittwoch, 14. September 2016 um 07:16 Uhr
> Von: "Tom Knox" 
> An: "Discussion of precise voltage measurement" 
> Betreff: Re: [volt-nuts] HP 3458A/HFL : looking for information/photos/fw
>
> Purchased new the HFL 3458A is exceptional. That said, it is my understanding 
> that the HFL has the exact same circuit topography but uses select parts. Now 
> here is where things get fuzzy, in the case of used 3458A's the parts often 
> improve with age. So it is difficult to know without characterizing you meter 
> as it ages as well as detailed knowledge/data on other 3458A's the degree of 
> improvement if any and therefore whether the expense would be justified. Or 
> if the new components would age as gracefully. I am not sure of exact 
> firmware differences, perhaps someone can add information on that. Over the 
> years I have seen a number of 3458A regardless of options that dramatically 
> exceed their specs. The point is if you have one of those "golden" 3458A's 
> don't let go of it. I hope that helps.
> 
> Cheers;
> 
> 
> Thomas Knox
> 
> 
> 
> 
> From: volt-nuts  on behalf of John Phillips 
> 
> Sent: Tuesday, September 13, 2016 10:23 PM
> To: Discussion of precise voltage measurement
> Subject: Re: [volt-nuts] HP 3458A/HFL : looking for information/photos/fw
> 
> While talking with hp I was told the options Fluke orders. All are
> available to anyone who wants to buy one.
> 
> On Tue, Sep 13, 2016 at 9:06 PM, Illya Tsemenko  wrote:
> 
> > Hello to all volt-nuts,
> >
> >
> >
> > Considering to pimp-up my DVM for a while, but would like to know first if
> > anyone here saw actual PCB photos or have any information of what hardware
> > actually different in Fluke's HFL version of 3458A. Based on Fluke's manual
> > DC reference (A9 PCBA) and reference resistors on A1 PCBA got improvements.
> > Firmware is also likely to be bit different, as HFL comes with
> > preprogrammed macro's on keypad.
> >
> >
> >
> > If anyone have information about HFL, or have access to such instrument,
> > I'd appreciate any hints and details.
> >
> >
> > ___
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> > To unsubscribe, go to https://www.febo.com/cgi-bin/
> > mailman/listinfo/volt-nuts
> > and follow the instructions there.
> >
> 
> 
> 
> --
> 
> *John Phillips*
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Re: [volt-nuts] Thermal EMF - more results

[acbern]

so far so good.
but what do we learn from this? the solder alloy is essentially irrelevant
 


> Gesendet: Mittwoch, 06. Juli 2016 um 15:42 Uhr
> Von: "Herbert Poetzl" 
> An: "Discussion of precise voltage measurement" 
> Betreff: Re: [volt-nuts] Thermal EMF - more results
>
> On Sun, Jul 03, 2016 at 12:33:04PM +0200, Andrea Baldoni wrote:
> > Hello.
> > I repeated the experiment with a better setup, I also added
> > some alloys that are already arrived. So far, a really "low"
> > EMF solder hasn't been identified.
> 
> > Measurements have been done between water ice point and boiling
> > point with Agilent 34401A. I don't expect the curves be linear,
> > but here it's assumed they are.
> 
> > Copper - Sn96.5/Ag3/Cu0.5 -> 3.35uV/K
> > Copper - Sn95.5/Ag3.8/Cu0.7 -> 3.22uV/K
> > Copper - Sn60/Pb40 -> 3.34uV/K
> > Copper - Pb92.5/Sn5/Ag2.5 -> 3.02uV/K
> 
> > Copper - Brass -> 3.30uV/K
> 
> > I am waiting for Sn96/Ag4, Sn99/Cu1.
> 
> Any plans on testing Sn42/Bi57.6/Ag0.4 ?
> 
> Thanks,
> Herbert
> 
> > Best regards,
> >  Andrea Baldoni
> > ___
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> > To unsubscribe, go to 
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Re: [volt-nuts] New scan of Solartron 7081 Service Manual is now available.

[acbern]

Dave,

great thing, thanks! could you not also post to xdefs or ko4bb? 
I guess more popular these days.

cheers


> Gesendet: Dienstag, 14. Juni 2016 um 14:27 Uhr
> Von: "David C. Partridge" 
> An: "'Discussion of precise voltage measurement'" 
> Betreff: Re: [volt-nuts] New scan of Solartron 7081 Service Manual is now 
> available.
>
> Now updated
> 
> -Original Message-
> From: volt-nuts [mailto:volt-nuts-boun...@febo.com] On Behalf Of David C. 
> Partridge
> Sent: 14 June 2016 10:41
> To: 'Discussion of precise voltage measurement'
> Subject: Re: [volt-nuts] New scan of Solartron 7081 Service Manual is now 
> available.
> 
> A quick update, I just noticed that I hadn't cleaned up all the scans of the 
> mechanical drawings (I thought I'd done all of them).
> 
> I'll clean those up and re-post the document.
> 
> Dave
> 
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Re: [volt-nuts] LTZ1000 project build

[acbern]

the issue of resistor drifts is mainly related to the amplifier (7 to 10V) gain 
resistors, the other resistor drifts do have a very limited impact on the 
output (see data sheet).



> Gesendet: Freitag, 03. Juni 2016 um 23:47 Uhr
> Von: "Lars Walenius" 
> An: "volt-nuts@febo.com" 
> Betreff: Re: [volt-nuts] LTZ1000 project build
>
> 
> My experience is that boxes makes the time constants for humidity longer but 
> does not take it away. Heating in boxes takes the change due to humidity down 
> a little but it doesn´t go away. I have had boxes with LM399 and amps for 
> 7-10v with wirewounds for more than 20 years and they have definitely had 
> seasonal variations. Also if you have a completely sealed box with varying 
> temperatures the relative humidity in the box changes if the humidity is not 
> close to zero.
> 
> A 10V 2ppm ref on Ebay was said to have no humidity effect but my unit 
> definitely varied about 20ppm due to humidity during a long humidity test. 
> One guess I have is that some units have much longer time constants due to 
> better sealing but I am quite sure it doesn´t go away complete. Another 
> problem with humidity I have seen is that you may be cheated by humidity 
> changing over the season and cancelling the aging. This happened during my 
> first tests of AD587KRZ many years ago. During the first four months two 
> samples both had less than 2ppm drift and the humidity in the room changed 
> from 45 to 25%RH so they looked very promising. But during the next four 
> months when the humidity went up they drifted 15ppm.
> 
> Probably the 5 and 2ppm/C versions is manufactured in the same way. The 
> humidity graph under severe humidity and temperature testing shows a 500pm 
> difference for your chosen resistors. So doesn´t say so much. Hopefully they 
> are below 1ppm/%RH with low loads.
> 
> Lars
> 
> Från: Ian Johnston
> Skickat: den 3 juni 2016 20:42
> Till: volt-nuts@febo.com
> Ämne: Re: [volt-nuts] LTZ1000 project build
> 
> Hi,
> 
> The product I designed to use the 2ppm/degC resistors is sealed in an
> enclosure where the LM399AH etc live, so I don't expect much problem
> with humidity.
> 
> I use 2K2, 3.3K, 10K & 22K.
> 
> It's the RG2012L series from Susumu:-
> 
> http://datasheet.octopart.com/RG2012L-103-L-T05-Susumu-datasheet-13139546.pdf
> http://www.susumu.co.jp/common/pdf/n_catalog_partition01_en.pdf
> 
> The 2nd PDF above is mainly for the 5ppm versions but does contains
> various graphs including humidity.
> 
> Ian.
> 
> 
> 
> On 03/06/2016 17:01, Lars Walenius wrote:
> > Hi,
> >
> > Do you have any idea of the aging and humidity sensitivity of these 2ppm/C 
> > resistors?
> >
> > I have tested many resistors during the years and my opinion is that tempco 
> > is not the biggest problem for normal nuts use but of course may be if you 
> > sell a product. For a nut it is quite easy to check the tempco but not 
> > aging and humidity sensitivity.
> >
> > Of the resistors I have tested it is only hermetical sealed resistors that 
> > I don´t see a humidity sensitivity on. Even if they are bulk metal foil, 
> > wire wounds or metal films with low tempco´s they seem to have very varying 
> > humidity sensitivity if not sealed. Lower values of resistance (100-1k) 
> > normally seems to be better than 10-100kohm values that in all families may 
> > have up to 1-2ppm/%RH.
> > Last year I bought wire wounds, to be used in a LTZ1000 based design, that 
> > were supposed to be insensitive to humidity but they were not. They were 
> > even worse than other brands of WW and had several months of time constant. 
> > After a while the manufacturer admitted that it was a problem in the 
> > manufacturing and they were humidity sensitive. So far I haven´t received a 
> > replacement.
> >
> > Of course if you have a resistor with 2ppm/%RH and a seasonal variation of 
> > 50%RH it is only maximum 1ppm seasonal variation on the output on the LTZ. 
> > That is not easy to measure for most of us nuts.
> >
> > Lars
> >
> > Från: i...@ianjohnston.com
> > Skickat: den 26 maj 2016 13:35
> > Till: il...@xdevs.com; 
> > volt-nuts@febo.com
> > Ämne: Re: [volt-nuts] LTZ1000 project build
> >
> > Hi all,
> >
> > TiN, out of interest I spent ages fishing for low ppm/degC resistors for my 
> > own reference..ended up with 2ppm units from DigiKey. Yes, they are 
> > expensive and send the BOM into the clouds!..so I know how you 
> > feel!
> >
> > Ian.
> >
> >
> > - Original Message -
> >   From: Illya Tsemenko [mailto:il...@xdevs.com]
> >   To: volt-nuts@febo.com
> >   Sent: Thu, 26 May 2016 18:42:54 +0800
> >   Subject: [volt-nuts] LTZ1000 project build
> >
> >   I'm glad my little project got so much attention. Worth to mention few
> > points regarding my (or any other LTZ1000) unit:
> >
> 

Re: [volt-nuts] ADA4522

[acbern]

not sure the TI filter circuitry, although very nice, is stable with the 
ADA4522. 
have not checked, but R2/C2 loop stabilizer may not work with ad4522.
would require analysis/test, but positive result would sure make this a great 
reference buffer amp.
if you do, would be nice if you let the group know.



> Gesendet: Samstag, 09. April 2016 um 00:38 Uhr
> Von: "Randy Evans" 
> An: "Discussion of precise voltage measurement" 
> Betreff: Re: [volt-nuts] ADA4522
>
> I would use a filter such as TI's SBVA010 app note, "Improved Voltage
> reference Filter has Several Advanatages" or the article by Walt Jung,
> "Build an Ultra-Low Noise Voltage Reference" in Electronic Design.
> 
> On Fri, Apr 8, 2016 at 1:02 AM,  wrote:
> 
> > Low frequency noise is very good, but is is high noise at about 800kHz
> > (chopper) and above (possible artifacts). That should be filtered,
> > depending on your application.
> > What did you foresee to get rid of it, or would you accept it? Simple RC
> > filter as indicated in the manual increases the output resistance.
> >
> >
> >
> >
> > > Gesendet: Freitag, 08. April 2016 um 03:35 Uhr
> > > Von: "Randy Evans" 
> > > An: "Discussion of precise voltage measurement" 
> > > Betreff: Re: [volt-nuts] ADA4522
> > >
> > > Sure, all good applications.  I am thinking of using it as an output
> > filter
> > > for a 10V reference to filter all noise above 10Hz,
> > >
> > > On Thu, Apr 7, 2016 at 6:27 PM, Daniel Mendes 
> > wrote:
> > >
> > > > Ada4522-2 and 4522-4 are stocked at mouser. What about summing all
> > outputs
> > > > to reduce noise? Or use as buffered outputs with good reverse
> > isolation...
> > > >
> > > > Daniel
> > > > Em 07/04/2016 13:31, "Randy Evans" 
> > escreveu:
> > > >
> > > > > Has anyone looked at the ADA4522 precision op amp from Analog
> > Devices.
> > > > It
> > > > > looks very intriguing with it's extremely low offset voltage drift
> > of 22
> > > > > nV/°C maximum.  The offset voltage is as high as 5 uV but this could
> > be
> > > > > nulled out and it should be very stable over temperature after
> > that.  It
> > > > > could be a great choice for a voltage reference circuit.  Looks quite
> > > > > inexpensive also, although AD only sell in tubes of 96 right now.
> > > > > ___
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Re: [volt-nuts] ADA4522

[acbern]

Low frequency noise is very good, but is is high noise at about 800kHz 
(chopper) and above (possible artifacts). That should be filtered, depending on 
your application. 
What did you foresee to get rid of it, or would you accept it? Simple RC filter 
as indicated in the manual increases the output resistance.




> Gesendet: Freitag, 08. April 2016 um 03:35 Uhr
> Von: "Randy Evans" 
> An: "Discussion of precise voltage measurement" 
> Betreff: Re: [volt-nuts] ADA4522
>
> Sure, all good applications.  I am thinking of using it as an output filter
> for a 10V reference to filter all noise above 10Hz,
> 
> On Thu, Apr 7, 2016 at 6:27 PM, Daniel Mendes  wrote:
> 
> > Ada4522-2 and 4522-4 are stocked at mouser. What about summing all outputs
> > to reduce noise? Or use as buffered outputs with good reverse isolation...
> >
> > Daniel
> > Em 07/04/2016 13:31, "Randy Evans"  escreveu:
> >
> > > Has anyone looked at the ADA4522 precision op amp from Analog Devices.
> > It
> > > looks very intriguing with it's extremely low offset voltage drift of 22
> > > nV/°C maximum.  The offset voltage is as high as 5 uV but this could be
> > > nulled out and it should be very stable over temperature after that.  It
> > > could be a great choice for a voltage reference circuit.  Looks quite
> > > inexpensive also, although AD only sell in tubes of 96 right now.
> > > ___
> > > 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.
> > >
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> > To unsubscribe, go to
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Re: [volt-nuts] Update on 7081 input / cable connector

[acbern]

well, are you sure that includes the bracket and so? I think I paid more than 
that about 1+ years ago.



> Gesendet: Freitag, 18. März 2016 um 03:56 Uhr
> Von: "Pete Lancashire" 
> An: "Discussion of precise voltage measurement" 
> Betreff: [volt-nuts] Update on 7081 input / cable connector
>
> Seems inflation has done its job
> 
> Just got the quote back, $91
> 
> -pete
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Re: [volt-nuts] Low-cost voltage reference questions

[acbern]

Charles and group, 
another persons opinion:

I guess the reference to the "standards" means those sold on ebay US. If so, I 
would think it is a false expectation this would meet 3ppm acc. guaranteed 
within a year.
There is a lengthy chat in eevblog about it, in case you are not aware, and 
while the unit typically may not be too bad, it is certainly not seriously a 
3ppm guaranteed standard (even in its best version). It starts with the 
traceability, and goes on with the design and build standard. Details in the 
blog. In summary, it is not even really spec'ed, also because it can't be (at 
least not close to what it seems to raise in expectations). But at that price, 
it would be unfair to expect more than a hobbyist item with relatively unclear 
real specs. But if you mean another item, let us know, I guess the group would 
be interested.
Keep in mind, the Fluke 732B is specified/guaranteed to 2ppm per year. There is 
data available from Fluke about 732B drifts ("Predictability of Solid State 
Zener References"), and it can be seen how hard it is for them to guarantee 
2ppm/year.
So I think your price target and spec expectation ("guaranteed to remain"...) 
just does not match. 

I would think a unit that has a traceable specification to a National Standard 
(including an error propagation analysis for the factory calibration how to get 
there), and be within say 5ppm a year, over a defined (limited) temperature 
range, with a good build standard (CU-TE spades, metal case, EMI filtering, 
PSU...), targeted at those who cannot afford/do not need a 732B could easily 
have a fair price of a couple hundred usd.
Other opinions welcome.


Cheers
Adrian


> Gesendet: Montag, 23. November 2015 um 23:26 Uhr
> Von: "Charles Steinmetz" 
> An: "Discussion of precise voltage measurement" 
> Betreff: Re: [volt-nuts] Low-cost voltage reference questions
>
> Russ wrote:
> 
> >What is considered the break-over point of precision with low uncertainty
> >versus cost to a group like this? Is there a rule-of-thumb for the cost of
> >each additional digit of precision after N digits?
> 
> One person's opinion:
> 
> To a group like this, I'd be inclined to say that interest begins at 
> a room-temperature (say, 20C +/- 3C) accuracy of 3ppm (i.e., 
> guaranteed to remain within 3ppm from 18-22C for at least one year 
> after purchase).  3 ppm is 0.0003%.  There is at least one 10v 
> reference with specifications in this ballpark available at an asking 
> price under $130 (I'm told the seller has accepted offers 
> significantly lower than this).
> 
> >If I sell someone a reference
> >that I've ascertained is 2.50163v @70.3 F with a calculated uncertainty, is
> >it valuable as a 0.1% reference even though the error may be much less,
> >like +/- 0.08%?
> 
> I, for one, do not consider 0.08% to be "much less" than 0.1%.  One 
> sneeze and it's out of spec.  Indeed, I would consider a claim of 
> 0.1% accuracy to be bordering on fraudulent based on a calibrated 
> measurement at 0.08%, unless the spec was qualified as "within 0.1% 
> at [temperature within 0.1C] as is, where is -- no claim as to 
> accuracy after it has been shipped to the buyer."
> 
> Speaking as someone with substantial commercial design experience, I 
> would never offer a voltage reference for sale as a claimed "0.1% 
> standard" that I did not have excellent justification for believing 
> would stay below 0.05% for a year over a several-degree range of 
> temperature and multiple trips across the country via commercial 
> carriers.  I wouldn't expect to be able to charge more than $10-15 
> for the product just described, and then only if the nominal output 
> voltage were 10v (I think you will find that there is a very strong 
> preference for 10v references over 5v, 2.5v, or other voltages).
> 
> Best regards,
> 
> Charles
> 
> 
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Re: [volt-nuts] Low-cost voltage reference questions

[acbern]

There are many things to factor in. Drift of reference itself over time and 
temperature (399 is 1ppm/K worst case alone, over say 10K, i.e. 23C+/-5K). 
Drift of the gain setting resistor is critical (assuming you have an amp 
generating 10V out of the 399 output voltage). and so on. 
Also, you need a precise reference to calibrate the units (low cal uncertainty 
and low drift).
Selection, statistical validation and aging is needed.
All doable but costly and more complicated than one might expect. 

Thats why I think the target price has to be reasonable, any thoughts here?




> Gesendet: Dienstag, 24. November 2015 um 10:05 Uhr
> Von: "Ian Johnston" 
> An: "Discussion of precise voltage measurement" 
> Betreff: Re: [volt-nuts] Low-cost voltage reference questions
>
> Hi all,
> 
> I can relate to this...and only last night I was pouring over it 
> wondering what to do!
> 
> I have just designed a Handheld Precision Digital Voltage 
> Source.LM399AH & uController controlled.
> 
> About to start selling them, and so I am writing the manual & spec sheet for 
> it...but can't decide without a years worth of data & testing behind me 
> what figures to use!
> I've got the reference, DAC and op-amp figures, all the tempo's I need etc 
> etc.
> 
> H!
> 
> Ian.
>  
> 
> 
> -Original Message-
> From: acb...@gmx.de
> To: volt-nuts@febo.com
> Date: Tue, 24 Nov 2015 09:35:24 +0100
> Subject: Re: [volt-nuts] Low-cost voltage reference questions
> 
> 
> Charles and group, 
> another persons opinion:
> 
> I guess the reference to the "standards" means those sold on ebay US. If so, 
> I would think it is a false expectation this would meet 3ppm acc. guaranteed 
> within a year.
> There is a lengthy chat in eevblog about it, in case you are not aware, and 
> while the unit typically may not be too bad, it is certainly not seriously a 
> 3ppm guaranteed standard (even in its best version). It starts with the 
> traceability, and goes on with the design and build standard. Details in the 
> blog. In summary, it is not even really spec'ed, also because it can't be 
> (at least not close to what it seems to raise in expectations). But at that 
> price, it would be unfair to expect more than a hobbyist item with 
> relatively unclear real specs. But if you mean another item, let us know, I 
> guess the group would be interested.
> Keep in mind, the Fluke 732B is specified/guaranteed to 2ppm per year. There 
> is data available from Fluke about 732B drifts ("Predictability of Solid 
> State Zener References"), and it can be seen how hard it is for them to 
> guarantee 2ppm/year.
> So I think your price target and spec expectation ("guaranteed to 
> remain"...) just does not match. 
> 
> I would think a unit that has a traceable specification to a National 
> Standard (including an error propagation analysis for the factory 
> calibration how to get there), and be within say 5ppm a year, over a defined 
> (limited) temperature range, with a good build standard (CU-TE spades, metal 
> case, EMI filtering, PSU...), targeted at those who cannot afford/do not 
> need a 732B could easily have a fair price of a couple hundred usd.
> Other opinions welcome.
> 
> 
> Cheers
> Adrian
> 
> 
> > Gesendet: Montag, 23. November 2015 um 23:26 Uhr
> > Von: "Charles Steinmetz" 
> > An: "Discussion of precise voltage measurement" 
> > Betreff: Re: [volt-nuts] Low-cost voltage reference questions
> >
> > Russ wrote:
> > 
> > >What is considered the break-over point of precision with low uncertainty
> > >versus cost to a group like this? Is there a rule-of-thumb for the cost 
> of
> > >each additional digit of precision after N digits?
> > 
> > One person's opinion:
> > 
> > To a group like this, I'd be inclined to say that interest begins at 
> > a room-temperature (say, 20C +/- 3C) accuracy of 3ppm (i.e., 
> > guaranteed to remain within 3ppm from 18-22C for at least one year 
> > after purchase).  3 ppm is 0.0003%.  There is at least one 10v 
> > reference with specifications in this ballpark available at an asking 
> > price under $130 (I'm told the seller has accepted offers 
> > significantly lower than this).
> > 
> > >If I sell someone a reference
> > >that I've ascertained is 2.50163v @70.3 F with a calculated uncertainty, 
> is
> > >it valuable as a 0.1% reference even though the error may be much less,
> > >like +/- 0.08%?
> > 
> > I, for one, do not consider 0.08% to be "much less" than 0.1%.  One 
> > sneeze and it's out of spec.  Indeed, I would consider a claim of 
> > 0.1% accuracy to be bordering on fraudulent based on a calibrated 
> > measurement at 0.08%, unless the spec was qualified as "within 0.1% 
> > at [temperature within 0.1C] as is, where is -- no claim as to 
> > accuracy after it has been shipped to the buyer."
> > 
> > Speaking as someone with substantial commercial design experience, I 
> > would never 

Re: [volt-nuts] U150 1920-8937 Relay Driver for HP 34401A

[acbern]

at keysight directly, e.g. on stock at keysight germany, less than 20 euro.


> Gesendet: Montag, 12. Oktober 2015 um 20:02 Uhr
> Von: starb...@uplink.net
> An: "Discussion of precise voltage measurement" 
> Betreff: [volt-nuts] U150 1920-8937 Relay Driver for HP 34401A
>
> Where to find a U150 1820-8937 relay driver for the HP 34401A multimeter?
> Thanks,
>   John
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Re: [volt-nuts] Anyone know how to make stable inductors?

[acbern]

I did a quick and dirty check, using a standard wire DUT adapter with my (not 
calibrated) 4275 meter and 2x 100R and 1x 1000pf. According to the guide below, 
this should reslt in 10uH.
Checked the parts allone with the meter before, all reasonably close to nominal.
One end of the resistors connected to the wire contacts each, other ends hooked 
up together and connected to the case through the 1nF capacitor. 
Not precise parts, ended up at about 9.9uH at 1MHz.
So while this is by no means any quantitive analysis, it seems to work in 
principle and would be worth building the real ones with shielded case.
Again, calibrating these meters does not require inductors, still it is a 
pretty interesting approach i think.


 Gesendet: Donnerstag, 20. August 2015 um 03:38 Uhr
 Von: Todd Micallef tmical...@gmail.com
 An: Discussion of precise voltage measurement volt-nuts@febo.com
 Betreff: Re: [volt-nuts] Anyone know how to make stable inductors?

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

[acbern]

Thats a great document, and certainly is a supperior method than doing some DIY 
coils, provided very stable resistors and capacitors are used. Resistors is 
straightforward. As capacitors, mica glass is recommended. There are some NOS 
russian mica high rel capacitors available for little money. I have used those 
as standards, however I have no history yet, since I only have the inital cal 
data, second cal verification is still pending, but since they are hermetic, 
and provided they are used at a constant temperature, should be very good.

It also annoys me that I would have to send C/L meters to calibration 
regularly. So having own standards is a solution, provided they are stable. 
Actually, the HP service manual of the older meters says no need to do L 
verification, as the measurement principle ensures that when doing C 
verifcation, L automatically is covered, since no good L standards for higher 
frequencies are available (which seems not really true as we have learnt). 
Should be true for the 4284A measurement principle too, but I have not checked.

The next question then is, how do you ensure that the drift of these DIY 
capacitors is good (it is just an assumption they are stable, and 50ppm per 
year is a challange!!. The IET 1404 primary standards are 20/40ppm only!!). 
Actually 50ppm may be pretty hard with anything else than a invar air 
capacitor. Now these hermetic invar 1404 air capacitors are availabe from time 
to time on ebay (also ESI SC1000), and thay have that guaranteed low drift over 
years. Most often they are quite expensive, but from time to time ony pops up 
at a reasonable price, got mine for about 500 usd. They could be used as a gold 
standard for at least one value. Together with an inductive decade transformer 
bridge other capacitances could be calibrated (the decade transformer principle 
ensures inherent calibration).
And third, one could build up a quadrature bridge and refer a capacitor to a 
resitor which can easily be measured. Thats how the national labs work to 
define capacitance values down to the sub-ppm accuracy (besids using calculable 
capacitors). Building such a quadrature bridge with relatively high accuracy 
(10E-5 at 10nF) is not too difficult, provided one has a decavider 7 digit ac 
voltage divider (e.g. for AC voltage calibration purposes) and a dual channel 
digital 16 bit DDS in the lab anyway.



 Gesendet: Donnerstag, 20. August 2015 um 03:38 Uhr
 Von: Todd Micallef tmical...@gmail.com
 An: Discussion of precise voltage measurement volt-nuts@febo.com
 Betreff: Re: [volt-nuts] Anyone know how to make stable inductors?

 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
 
 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,
  

Re: [volt-nuts] Test Leads

[acbern]

the best is really to use bare copper wires, such as used for wiring bells at 
home. does not look fancy, but low EMF.
Re. the low EMF Pomona cables with 4mm plugs, when you insert them in their 
(Pomona's) low EMF binding terminals, the spring that activates the safty 
protection pushes them out slowly, same with other binding posts, so not a safe 
connection if you are not carefull. Badly engineered imo.
I made my own cables with spades, using high quality gold plated pure copper 
spades and kapton twisted shielded cables, but again, bare copper is better 
(see guildline video on youtube re. their resistance bridges), but you will 
probably, if at all, only see that with a 34420A in lowest resolution (actually 
I have not).



 Gesendet: Dienstag, 21. Juli 2015 um 18:33 Uhr
 Von: Randy Evans randyevans2...@gmail.com
 An: volt-nuts@febo.com volt-nuts@febo.com
 Betreff: [volt-nuts] Test Leads

 I recently acquired a Fluke 752A to go with my Fluke 732A and HP-3458A.
 Now I need to address the need for low thermal test leads.  Does anyone
 have any suggestions for test leads that have low thermal contributions to
 measurements?  I have looked at Pomona 1756 Low Thermal EMF Cables as a
 starting point but haven't found any other candidates.
 
 I have heard that old TV twin lead works well since most are stranded
 copper wire.  I have tried it between my 732A and 3458A and it seems to
 work fine but I would like to use more professional looking test leads,
 particularly with correct copper spade lugs (Pomona 2305 Low thermal EMF
 spade lug, Gold-plated?).  Any other suggestions?
 
 Thanks,
 
 Randy Evans AE6YG
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Re: [volt-nuts] Bls: Bls: How accurate is a fluke after 9 years

[acbern]

it is this resistor, in its z-foil version.
they can be ordered from vpg distributors also in small qty (some may have a 
min. order value), lead time is usually pretty high.


 Gesendet: Montag, 18. Mai 2015 um 02:39 Uhr
 Von: Anton Moehammad via volt-nuts volt-nuts@febo.com
 An: Discussion of precise voltage measurement volt-nuts@febo.com
 Betreff: [volt-nuts] Bls:  Bls:  How accurate is a fluke after 9 years

 Hi All,
 in the Vishay web I found a better in spec resistor than  vha512, could 
 somebody give a comment ? 
 http://www.vishaypg.com/docs/63120/hzseries.pdfThey also offer non standard 
 value, anybody has experience in Vishay non standard value ?
 
 Thank You
 
 
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Re: [volt-nuts] *WAY* too expensive for even Keysight to redesign

[acbern]

Hello,
Your last statement actually could be a nice project in one of the well known 
blogs... 
I have thought about this as well. It should not be too complicated to do that. 
The core components the stability are defined through are not that many. ac 
current may be an issue though (I have seen surprising things using precision 
resistors for AC current measurements).

Regarding ohms transfer stability, the way to go may be, since we cannot do an 
error budget analysis of the circuitry, not knowing all the internals with 
enough detail (although the CLIP is readily available), to do a statistical 
analysis for each specific instrument the owner wants to qualify, say at the 
full digit (so. e.g. 10k) in accordance with GUM, to come up with data similar 
to what the Solartron 7071/81 has.


cheers

adrian




 Gesendet: Freitag, 08. Mai 2015 um 14:38 Uhr
 Von: frank.stellm...@freenet.de
 An: Volt-Nuts volt-nuts@febo.com
 Betreff: [volt-nuts] *WAY* too expensive for even Keysight to redesign

 Hello,
  
 Joe Geller once collected 3458A serial numbers, and concluded, that this 
 instrument maybe sold to about 50k units in these 25 years. It's not clear, 
 if it's still sold by high numbers, but the total turnover might have been 
 around 400M$, or 16M$/yr.
  
 In the end, that should be enough to finance a redesign, or a model facelift.
 This is urgently necessary, even if Keysight would not see a totally new or 
 increasing market for 8.5 digits DMMs, but only wants to still offer this 
 instrument 'as-is'.
 Many components of the 3458A are already obsolete, or endangered by PTNs, not 
 to speak about all these through-hole components. I've already seen pictures 
 about a piggy-back solutions for several ICs, and maybe they have to use that 
 already for the new production, especially the two fast comparators EL2010, 
 U142  U181, used with the A/D.
 The 68HC000 is also obsolete in the DIL package, and the SMD package is 'not 
 for new design' already.
  
 Therefore, a complete redesign, including the software architecture, is more 
 reasonable.
  
 Keysight would need the budget for that, but they are meanwhile also lacking 
 the brains, which have mostly left the company (Wayne C. Goeke, the inventor 
 of the A/D, joined Keithley, and Ronald L. Swerlein, the God-father of the 
 ACV processing, well he's retired, for some personal reasons, obviously).
  
 Then, another big problem would arise, that is the verification/validation of 
 the traceability of the 2 source / autocalibration feature.
 It would be not so easy to again achieve the acceptance of the 'metrological 
 community', if any of the crucial parts of this instrument would be touched.
 I assume, this direct acceptance in 1989 was only due to the close 
 cooperation with the NBS then, when they validated the ~0.02ppm linearity by 
 means of the new JJ array.
 
 I have read a lot about the history of the very similar FLUKE 5700/5720 
 artefact calibration.
 In contrast, it took FLUKE several years, before their instruments 
 experienced the same reputation.
  
 Well, the 3458A was designed for metrological use in 2nd instance only, due 
 to the 55°C ambient operating temperature, and these many compromises they 
 had to make concerning stability.. especially the LTZ1000A reference could 
 have been optimized greatly (8x) with 20°C lower ambient requirements, and a 
 bit more cleverness.
 Regarding this aspect, please compare the stability specs to other real 
 metrological instruments, like the FLUKE 732A/B, the 7001, and the 1281 / 
 8508A 8.5digits DMM.
  
 So, the 3458A was  mainly intended for military conditions, but also for 
 harsh industrial application, e.g. end of line testing at the manufacturing 
 line, where laboratory conditions can not be maintained.
  
 I also think, that the mediocre / cheap (copy-and-paste) design of these new 
 6.5 .. 7.5 digits DMMs still leaves a big field of other applications for 
 precise 8.5 digits DMMs, as it always has been..
 .
 I used this instrument already in 1990, at university, for high SNR, low 
 distortion digitizing @ 16bit/100kHz or 18bit/50kHz, down to -100dB / 0.001%, 
 single shot.
 The 3458A may still be benchmark in this category, probably also compared to 
 modern delta sigma A/Ds, but for sure compared to the recent, new 6.5 and 7.5 
 DMMs.
 For my experiments, I also had the necessity to design and to adjust several 
 precision current sources, DCI  0.01%, ACI  0.05%.
 That's not yet a true 'metrological' application.. But if you study the 
 specifications of these new DMMs, even the 7.5digits 344470A will still not 
 manage that level of uncertainty, if you take the 90 days spec, or their 
 T.C.s.
  
 Generally, their crucial parameters do not fit their resolution.
 All of them have an A/D (multislope IV), wich are linear to 1..3 ppm only.
 A 7.5 digit instrument would instead require 0.1ppm linearity, otherwise the 
 resolution is useless. For that reason also, the featured autocal 

Re: [volt-nuts] Advise to Junior Member Regarding Acquisition of Fluke 5XXX Series Calibrator

[acbern]

A few things to keep in mind:
- the 720A (and the 752A) are self-calibrating, i.e. you can (easily) calibrate 
it yourself before use. The 3458A, using its external artifact self-cal 
procedure based on only 10v and 10k, requires a performance verification 
therafter (at least every second time, see some military docs concluding this, 
I don't recall the link but easy to find; i would actually say, to comply with 
GUM, every time).
-the linearity of the 3458a is excellent and not beatable up to a 1:10 ratio, 
beyond that (e.g. if you want to calibrate an instruments 1000v or 100mV range 
form a 10V reference), it is not usable, again the 720a or 752A are superior.

So to summarize, if you want to be selfstanding, and do your calibrations with 
reference to an externally calibarted 10v and 10k resistor only, you need a 
good voltage source (5440 is hard to beat even by the 5720A, and can replace, 
with some compromises, also a 732a if need be), a 3458A but also some type of 
self-cal 1:10 and 1:100 divider (720A or 752 or similar). You could build a 
hammon divider (1:10 and 1:100) yourself, for much less than a 720A costs, and 
since it is self-cal, if you do it right, you do not need to compromise on 
accuracy. what you really need is just the decade divide ratios to do all the 
3458A validation, and then go from there. all the gazillion other ratios that 
the 720a offers are really not needed then.

Adrian



 Gesendet: Donnerstag, 23. April 2015 um 21:19 Uhr
 Von: Frank Stellmach frank.stellm...@freenet.de
 An: volt-nuts@febo.com
 Betreff: [volt-nuts] Advise to Junior Member Regarding Acquisition of Fluke   
 5XXX Series Calibrator

 Hi Stan,
 
 the 720A can easily be replaced by an HP3458A, which is superior to the 
 KV divider in several aspects.
 
 First, the 3458A has 3-10 times better linearity, 0.02ppm (typ.) of F.S. 
 compared to 0.1ppm of input for the 720A.
 Therefore, a 10:1 transfer is accurate to 1ppm for the 720A only, 
 whereas the 3458A manages 0.1 to 0.3 ppm.
 
 The self calibration is much easier on the 3458A, as are all these 
 calibration measurements, you mentioned.
 (Fluke has published a good application note, how to replace their own 
 old style equipment as KV, Null VM, etc. by their own 8 1/2 digit 8508A).
 
 And you may get a very reasonable and recent instruments for 3000$/€, 
 maybe much less for older ones.
 
 
 A calibrator is limited in use, as it needs a Null VM at least.
 
 Anyhow, I recommend the Fluke 5440A / 5442A DCV calibrators.
 
 They are ultra stable, having 2 stacked SZ263A references inside, good 
 for 732A stability.
 
 Their D/A is also extremely linear, I measured something like 0.2ppm INL 
 against my 3458A, and they are spec'd to 0.5ppm of output, also superior 
 to the 720A in some volt areas.
 
 They also have this handy autocal function (like the 3458A) for the 4 
 higher volt ranges ( 11, 22, 220, 1000V),  once that they are externally 
 calibrated, and because their internal component drift is low, after 
 these years.
 That means, as their internal reference is very stable, you may bring it 
 near 24hr. specification, every time you do the autocal.
 I could not measure any deviation to that, using my 3458A, plus a self 
 built precision Hammon divider for 1kV.
 
 Their autocal feature is not explicitely promoted, but you will find 
 that description between the lines in the addendum of the user manual.
 
 Only the 1V and 100mV range have to be externally calibrated quite often.
 
 These instruments may cost about 2000$/€.
 
 So you better have both, the 5440 and the 3458A.
 
 Frank
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Re: [volt-nuts] AC voltage standards.

[acbern]

these instruments are painfull to use, complex measurement procedures and 
pretty unstable (if you want to use their ppm resolution). I spend hours and 
hours calibrating a set. lots of data available from standards labs.
what I would recommend is a ballantine 1605A. easy to use, very precise, well 
priced, broad frequency range but needs to be calibrated of course as well. you 
could go from one single calibrated thermal converter (e.g. 10V) and with e.g. 
a nanovoltmeter (34420A)  you could do a full 1605 ladder calibration. poor 
man's 792...





 Gesendet: Donnerstag, 09. April 2015 um 21:17 Uhr
 Von: Chuck Harris cfhar...@erols.com
 An: Discussion of precise voltage measurement volt-nuts@febo.com
 Betreff: Re: [volt-nuts] AC voltage standards.

 Those are not references, but rather are AC thermal
 transfer standards.
 
 The way they work is you apply an unknown AC voltage
 to it, and measure the DC voltage generated by
 its thermocouple.  Then you remove the AC voltage,
 and apply a DC voltage that gives the same thermocouple
 voltage.  Usually, you apply the DC voltage with both
 polarities, and average the two readings... which helps
 to null out any thermocouple errors.
 
 To successfully use an AC thermal transfer standard it
 helps to have the controller instrument that goes along
 with it.
 
 Fluke makes as nice setup, as did HP.
 
 At their best, they are twidgety, and quite sensitive to
 ambient temperature variations, physical orientation,
 air currents  Apply too much voltage, and like the
 light bulbs that they resemble, they go poof!
 
 I don't think any metrologist has ever been truly happy
 with the AC thermo transfer standard.
 
 -Chuck Harris
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Re: [volt-nuts] Calibration of voltage standards

[acbern]

the 3458A is very well suited as a nullmeter (there e.g. also is an appnote 
from Fluke on this). I have checked this against other meters such as the e.g. 
the keithley 155 and 34420A, and for my setup (Fluke 732A, Datron 4910 and 
others) I have the least problems with noise, common mode issues and so.
The nullmeter method should only be used when the DUT is adjusted. ie., low 
voltages differnces of a few mV should not be measured, the accuracy is, at 
least formally, not specified there sufficiently precise.
The second method frequently used and that I am using most of the time (since I 
do not adjust references, especially the 732A is known to potentially increase 
its drift thereafter, the 4910 uses digital adjustment, so there it would be 
ok) is to measure the absolute voltage of both standards with a 3458A and 
reference the DUT to the standard. This can be done because of the excellent 
linearity of the 3458A. If I remember correctly the accuracy related to the 
standard is in the 0,1ppm range at 10V.





 Gesendet: Mittwoch, 11. Februar 2015 um 08:36 Uhr
 Von: Chuck Harris cfhar...@erols.com
 An: Discussion of precise voltage measurement volt-nuts@febo.com
 Betreff: Re: [volt-nuts] Calibration of voltage standards

 To do a comparison of the sort you are asking about, the
 sensitivity of the null meter is much more important than
 its ultimate accuracy.
 
 So, neither of your meters is really the right meter to
 use for this task.  What you want is called a null meter,
 and is generally sensitive to the microvolt region.
 
 -Chuck Harris
 
 Ken Peek wrote:
  Hi Group,
 
  I have heard of a few different ways to measure one 10V voltage standard
  against another 10V voltage standard.
 
  Assume we have two 10V voltage standards.  One is calibrated, the other
  not only needs to be calibrated, but probably adjusted.  For the sake of
  simplicity, let's say the two standards are Fluke 732B's.
 
  I *think* the best way is to connect the two units' (-) terminals
  together, then connect a calibrated meter in between the (+) terminals,
  and measure the difference.  I have also heard that to remove thermal
  EMFs, you should use a low-thermal-EMF DPDT switch or a low-thermal-EMF
  relay to reverse the connections on the DMM, so you can take the reading
  forward and reversed, then split the difference.  There is the
  possibility to introduce thermal-EMF errors from the switch/relay as
  well, so I'm wondering if this is a good idea.  This sort of makes sense
  to me, but I'm not a metrologist, so I would like to hear what others in
  this group think about this.
 
  So, just what is the proper way to accomplish this task?
 
  BTW-- I have an Agilent 34420A and an HP 3458A, which would be the
  better instrument for this task?
 
  Best Regards,
  Ken Peek
  =
 
 
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Re: [volt-nuts] Checking an LCR meter

[acbern]

I have a smiliar issue, so interesting to read this. Mine is related to older 
gear like 4192a and 4275A meters which I am using. All these old meters, if 
properly adjusted an calibrated, are very good meters, you can repair them 
yourself, and are very cost efficient (what did you pay for our 4284 if I may 
ask, I find them still pretty expensive). Newer gear, as you stated, did not 
add much higher percision if at all (I was told by professional seller of used 
gear that this is why they are very much demanded, he cennot get enough of 
them).

I too do not want to spend the money for getting these meters calibrated on a 
regular basis, it would cost a fortune over time. The same issue applies to my 
other gear, so I have decided I have a few basic standards calibrated 
externally on a regular basis, and the rest is calibrated from there: 
My standards are voltage (10V 732a/4910), resistance (10k, SR104), rf level 
(nrp z 55, power sensor dc to 40ghz), and lower frequency thermal converter. 
The rest is then calibrated by trsnsfer measurements (in a traceable manner). 
The 3458A e.g. is always good for ratio measurements because of its excellent 
linearity, so with a stable voltage source, one can calibrate resistors from 
1ohm to 1mohm easily and precisely. Just as an example. On a ide not e.g. I 
have my 732a 10V calibrated only (to  0,5ppm acc.), and do the 1V calibration 
with the 3458A. One can do that more often, as this output is less stable, 
using a 3458A, and saves money externally too.

To your question: today the capacitance is derived in national standard labs 
from the quantum ohm by quadrature bridges. There also is a calculable 
capacitor model being used (earlier), but this requires precise machining, and 
I have not further considered this. Quadrature bridges as used in standard labs 
are accurate to 1ppm. These are lab setups with cables flying arround, built 
up by a set of special transformers, dds generators, lock-in amp detector 
amplifiers and so on, so these are no special all-in-one meters. Others have 
shown/reported that pretty basic lab bridges using standard stuff (7 digit 
ratio transformers, standard dds generators, precision ac level meters) are 
still good to 10e-5, which is pretty precise. Dont get me wrong, this still 
requires expensive and precision gear, but nothig very special (e.g. no special 
custom made transformers and stuff).
So I am currently preparing a setup of a coaxial quadrature bridge. A 1000pf 
coaxial capacitor (gr type), these are reasonably cheap and very stable, and as 
standard a 10kohm coaxial resistor will be used. This can be build using rf 
cases and a good, low ppm/k resistor. I am still trying to figure out the math 
re. error propagation (e.g., how does a potential phase error of the dds 
generator needed to generate the quadrature signal translate into a mesurement 
tolerance). There is some data online, some with a download fee, and also books.
So with this setup, one can precisely calibrate a 1000pf capacitor. The gear 
needed may sound a little expensive, but I have it anyway, amongst other 
reasons also to calibrate my other stuff (e.g the ratio transformer is used for 
ac meter and calibrator cal.), so all I needed in addition is the capacitors 
(actually I bought gr types from 1pf to 1000pf) and the coaxial cabling setup 
which is a litte special related to the ratio transformer, rest is just bnc 
cabling. These gr capacitors have very little drift, they are air capacitors 
built from sheet metal with temp elong. coefficient of essentially 0. This 
allows that they are calibrated say every 2 years or more (cal labs do that 
too).
I did also buy some time ago russian hermetic glas mica capacitors, which I had 
calibrated externally, so it will be interesting to see how they aged. (These 
should be fairly stable, if you want one let me know). I installed them into a 
rf box with 4 bnc connectors (similar to the ones used as standard cal devices 
by Agilent). For the gr capacitors, you need an adapter between the gr874 
connectors and the 4 BNCs. You also need to build this. 
Thats all then for the 1000pF. The other capacitors can then be calibrated with 
a similar setup using again the ratio transformer in a capacitor bridge setup. 
And one needs the math behind to derive the accuracies of the measurements. As 
you plan to do an initial cal of your meter externally, you could vaildate the 
bridge tolerance calculations. (Actually we could later also exchange 
capacitors to validate results, I have done that with a voltnut here in Germany 
on some other stuff some time ago.)
Then you also need shorts and opens and resistors in shielded cases, this is 
straigtforward though, I had built them up some time ago already for my meters.

cheers



 Gesendet: Freitag, 06. Februar 2015 um 23:10 Uhr
 Von: Dr. David Kirkby (Kirkby Microwave Ltd) 
 drkir...@kirkbymicrowave.co.uk
 An: Discussion of precise voltage measurement volt-nuts@febo.com
 

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

[acbern]

this would be over-engineered, unless you have a lot of spare time or want to 
do this for fun. If you use plastic supports as they were used when these TO 
packages were common (these supports should still be available, they surround 
all pins and quality plastics were standard) and use any cap in addition on top 
of the case, thats enough blocking of airflow. you would put that into a closed 
box anyhow, with no air flow through fans or so.



 Gesendet: Mittwoch, 28. Januar 2015 um 15:00 Uhr
 Von: J. L. Trantham jlt...@att.net
 An: 'Discussion of precise voltage measurement' volt-nuts@febo.com
 Betreff: Re: [volt-nuts] plastic caps on 3458A reference board

 Frank,
 
 Thanks for the info.  I've wondered about that.
 
 In the days of 3D printers and CAD/CAM, it might be possible to have a 'run' 
 of these 'made to order', so to speak.
 
 I wonder if Linear Technology would have any information about them?
 
 Thanks again.
 
 Joe
 
 -Original Message-
 From: volt-nuts [mailto:volt-nuts-boun...@febo.com] On Behalf Of Frank 
 Stellmach
 Sent: Wednesday, January 28, 2015 5:28 AM
 To: volt-nuts@febo.com
 Subject: [volt-nuts] plastic caps on 3458A reference board
 
 Hello Joe,
 
 yes the cap consists of two parts.
 The upper one serves for thermal isolation of the LTZ1000A TO99 case against 
 the environment and therefore reduces the power dissipation of the oven.
 
 The part on the solder side is much more important, as it covers the solder 
 joints and avoids air draught over these pins. That avoids these low 
 frequency voltage variations, which are mentioned in the LTZ data sheet.
 
 Anyhow, there are no further shieldings around the PCB, so the solder joints 
 of the OP Amp and the precision resistors are exposed to that air draught, 
 maybe from the fan.
 That's a further engineering fault they made on this reference.
 
 (The other faults are the 95°C oven temperature, the use of the A version 
 instead of the non A, and the use of R417,200k temperature compensation 
 resistor, which is necessary for the non A version only.)
 
 The hat is not included in the BOM inside the CLIP, therefore can not be 
 ordered from HP, obviously.
 
 It is a smooth, shiny plastic, resembles the one used around the LM399H.
 Wasn't latter one something like polysulphone?
 
 Maybe suitable pieces of polystyrol foam will do the job also.
 
 Frank
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Re: [volt-nuts] Old HP3458A - SN: 2823A 03939

[acbern]

hi
the EPROMs are in sockets, no soldering needed.
but again, buying a precision instrument but reprogramming cal data that is 
years old does not make any sense.
unless of course if you are just a collector and do not use its accuracy.
adrian


 Gesendet: Dienstag, 07. Oktober 2014 um 16:35 Uhr
 Von: cfo xne...@luna.dyndns.dk
 An: volt-nuts@febo.com
 Betreff: Re: [volt-nuts] Old HP3458A - SN: 2823A 03939

 I'm now the proud owner of a HP 3458A OPT-002.
 
 I have adapted Mark's 3458A CalRam program to use linux-gpib , and have 
 made backups of the calram , and the dataram.
 
 I will get a new calram : 
 http://tinyurl.com/mggqmos
 
 And 2 x dataram : 
 http://tinyurl.com/otspeek
 
 
 I'll  get 4 x 32k SRAM for opt 001 - hopefully these are correct. 
 http://tinyurl.com/kjbtcla
 
 
 Does anyone know if the Eproms are already in sockets ?
 
 I was planning on installing sockets for the calram , datarams , but have 
 hoped the eeproms was already in sockets.
 
 
 TIA
 CFO - Denmark
 
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Re: [volt-nuts] Old HP3458A - SN: 2823A 03939

[acbern]

well, I do that with my references if they cannot be adjusted reasonably such 
as the 732a. but for meters and calibrators I do not. 
achievieng high precison with such an instrument then means you still need to 
characterize it (i.e. calibrate, and not adjust it, doesnt save money 
essentially)
and secondly you always need to apply a transfer factor, i am too lazy for 
that, i rather get it adjusted when i cal it.
also, the reference is stable, true, but other things do drift, and we talk 10+ 
yeras here (last cal sticker i saw). it would certainly be interesting to know 
where its different ranges went inbetween (if it was known that it was adjusted 
to within spec back then, which probably is not known)


 Gesendet: Mittwoch, 08. Oktober 2014 um 10:32 Uhr
 Von: Mike S mi...@flatsurface.com
 An: volt-nuts@febo.com
 Betreff: Re: [volt-nuts] Old HP3458A - SN: 2823A 03939

 On 10/8/2014 4:23 AM, acb...@gmx.de wrote:
  the EPROMs are in sockets, no soldering needed.
  but again, buying a precision instrument but reprogramming cal data that is 
  years old does not make any sense.
  unless of course if you are just a collector and do not use its accuracy.
 
 It makes perfect sense, for the same reason that HP doesn't touch the 
 cal if it's in spec - for tracking/characterization. By keeping the same 
 cal constants, if and when he does send it in for calibration he'll be 
 able to know how much it drifted since it was last cal'd (25 years ago?).
 
 -- 
 Mike
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Re: [volt-nuts] Datron 4920M, AC Voltmeter, for sale on ebay - 1 day left

[acbern]

folks,

does anybody know the difference in specs between a 4920M and the standard 
4920. No data on the web.

thanks



 Gesendet: Sonntag, 31. August 2014 um 23:41 Uhr
 Von: Charles Black cbl...@centurytel.net
 An: Discussion of precise voltage measurement volt-nuts@febo.com
 Betreff: Re: [volt-nuts] Datron 4920M, AC Voltmeter, for sale on ebay - 1 day 
 left

 Hi Stephen,
 
 Thanks for the info on the 4920M. It might be that I should pass on this 
 but it is nice to know that it is probably working. If I don't have the 
 necessary items needed for calibration it might still be a good source 
 uncalibrated.
 
 I was hoping that the 4920 had better minimum voltage out steps than my 
 present Rigol 4062 for 3458a AC calibration. I have two EL 1400 0.25V 
 voltage thermal converters that I was trying to use in a test setup but 
 they had such a low voltage range that I was forced to use my ATV-60 
 attenuator. It all kind of worked but a 0.1 db minimum step  is a little 
 course for easy use. The Rigol also suffers from this malady.
 
 Charlie
 
 On 8/31/2014 1:06 PM, Stephen Grady wrote:
  Charlie,
 
 
  The Error Ur is an under-range error; you have to apply an input above 
  10% of the range before it will display a reading. The 4920's are a very 
  nice instrument. Their only problem is that they are all so old that they 
  are reaching the stage where some components are drifting excessively or 
  failing. I have come across 4920's that are drifting a little (more than 
  there spec) between cals (and yes they need to be cal'd annually), another 
  4920 I came across had an intermittent failure in one of its power supplies.
 
  Kind Regards,
 
  Stephen Grady
  Sydney Australia
 
  -Original Message-
  From: volt-nuts [mailto:volt-nuts-boun...@febo.com] On Behalf Of Charles 
  Black
  Sent: Monday, 1 September 2014 3:19 AM
  To: b...@veritechmeasurements.com.au; Discussion of precise voltage 
  measurement
  Subject: Re: [volt-nuts] Datron 4920M, AC Voltmeter, for sale on ebay - 1 
  day left
 
  Hi Ben,
 
  I am going to check this out today to find if it might be helpfull around 
  here for my AC calibration. It has an error message: Error Ur
  so some fixing is going to be needed. On the back it says it's got Option 
  80, whatever that is.
 
  Charlie
 
 
  On 8/31/2014 5:37 AM, ben wrote:
  Hello all,
  Just a heads up. I noted there is a lonely Datron / Wavetek 4920M AC
  voltmeter for sale on ebay, starting at US$650 (ending in 1 day !). I
  have little idea of its true working state or not (picture shows it 
  powered on).
  If fully working it would be a good buy for an AC voltmeter that is, I
  reckon, better than an HP 3458A. Only drawback with these models is
  the voltage input shell is always earthed, not floating. I have two of
  these 4920M's already, not really tempted by a third. I have a paper
  copies of operator, calibration, and service manual if anyone interested.
 
  regards,   ben.
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[volt-nuts] Using a DVM to adjust a 752a divider

[acbern]

Resend as it did not go to the group (please also see my question at the end of 
my mail):


mitch,

you bring up a good point. I did not know the document, thanks for sharing. it 
inspired me to do some measurements, thats why it took a while to respond. the 
results were quite surprising to me.

i did test the 752a with the following gear:
-keithely 182-m (this is a 182 nanovoltmeter that has an internal 9v battery in 
its input stage, i compared it with a standard 182 some time ago and it did 
have about half its peak to peak noise. have not found any data on it on the 
web btw.)
-34420a nanovoltmeter
-keithley 2182 nanovoltmeter
-3458a
-keithley 155 (in battery operated mode)

my results in a nutshell:
besides the 40k source test as mentioned in the app-note, i also tested them 
with the 752a in cal mode and the input voltage of the source (5440a) set to 0 
(so besides some small emf-vltages, the result should be 0 after temp 
stabilization). 

only the 2182 had 1+uv input measurement when doing the 40k-test, meaning all 
others, since they passed the test, should be usable. but it also turned out 
that the reading when connected to the 752a with uin = 0v, was not acceptable 
for others. this may also have had to do with some ground loop issues, although 
quick checks did not reveal any obvious issues (and there was no issue with 
loops with those meters that passed).

so at the end of the day, the only usable devices in my test were the 3458a and 
the 155. 


what I found as well, unfortunatelly, was that my 752a had an issue in the 
1:100 range. I had not used it for half a year or so, and when i tried to 
calibrate it, everything was fine at 1:10, but I could not zero at 1:100. 
consistent redings with both 3458a and 155. drift relatively unstable and in 
the -500uv range, so pretty high deviation. also, after I had then set the 
internal tune setting resistors to zero (so I cannot go below), there still 
remains an offset of a few hundred uv. 

anybody had similar experience with the 752a? 


thanks
adrian


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Re: [volt-nuts] Datron 4920M, AC Voltmeter, for sale on ebay - 1 day left

[acbern]

thanks, I would welcome comments on calibration too.



 Gesendet: Dienstag, 02. September 2014 um 12:23 Uhr
 Von: Stephen Grady grady.st...@gmail.com
 An: 'Discussion of precise voltage measurement' volt-nuts@febo.com
 Betreff: Re: [volt-nuts] Datron 4920M, AC Voltmeter, for sale on ebay - 1 day 
 left

 The Datron 4920M was a special version of the 4920 made for the military, the 
 major difference is the M version has a 50 Ohm (N-female) wideband input and 
 only the N-female input for the low frequency input. Whereas the 4920 has a 
 Binding Post Input as well as the N-female input. I am not aware of the specs 
 for the wideband input but the low frequency input will be the same for both 
 models.
 
 I intend to reply in some detail soon on the calibration of these instruments 
 (and this will also apply to the Fluke 5790) and the principals of AC 
 calibration below 100mV as Charles has raised the issue of using attenuators 
 to do lower voltage measurements.
 
 Kind Regards,
 
 Stephen Grady
 Sydney, Australia
 
 -Original Message-
 From: volt-nuts [mailto:volt-nuts-boun...@febo.com] On Behalf Of acb...@gmx.de
 Sent: Tuesday, 2 September 2014 5:54 PM
 To: Discussion of precise voltage measurement
 Subject: Re: [volt-nuts] Datron 4920M, AC Voltmeter, for sale on ebay - 1 day 
 left
 
 folks,
 
 does anybody know the difference in specs between a 4920M and the standard 
 4920. No data on the web.
 
 thanks
 
 
 
  Gesendet: Sonntag, 31. August 2014 um 23:41 Uhr
  Von: Charles Black cbl...@centurytel.net
  An: Discussion of precise voltage measurement volt-nuts@febo.com
  Betreff: Re: [volt-nuts] Datron 4920M, AC Voltmeter, for sale on ebay 
  - 1 day left
 
  Hi Stephen,
  
  Thanks for the info on the 4920M. It might be that I should pass on 
  this but it is nice to know that it is probably working. If I don't 
  have the necessary items needed for calibration it might still be a 
  good source uncalibrated.
  
  I was hoping that the 4920 had better minimum voltage out steps than 
  my present Rigol 4062 for 3458a AC calibration. I have two EL 1400 
  0.25V voltage thermal converters that I was trying to use in a test 
  setup but they had such a low voltage range that I was forced to use 
  my ATV-60 attenuator. It all kind of worked but a 0.1 db minimum step  
  is a little course for easy use. The Rigol also suffers from this malady.
  
  Charlie
  
  On 8/31/2014 1:06 PM, Stephen Grady wrote:
   Charlie,
  
  
   The Error Ur is an under-range error; you have to apply an input above 
   10% of the range before it will display a reading. The 4920's are a very 
   nice instrument. Their only problem is that they are all so old that they 
   are reaching the stage where some components are drifting excessively or 
   failing. I have come across 4920's that are drifting a little (more than 
   there spec) between cals (and yes they need to be cal'd annually), 
   another 4920 I came across had an intermittent failure in one of its 
   power supplies.
  
   Kind Regards,
  
   Stephen Grady
   Sydney Australia
  
   -Original Message-
   From: volt-nuts [mailto:volt-nuts-boun...@febo.com] On Behalf Of 
   Charles Black
   Sent: Monday, 1 September 2014 3:19 AM
   To: b...@veritechmeasurements.com.au; Discussion of precise voltage 
   measurement
   Subject: Re: [volt-nuts] Datron 4920M, AC Voltmeter, for sale on 
   ebay - 1 day left
  
   Hi Ben,
  
   I am going to check this out today to find if it might be helpfull around 
   here for my AC calibration. It has an error message: Error Ur
   so some fixing is going to be needed. On the back it says it's got Option 
   80, whatever that is.
  
   Charlie
  
  
   On 8/31/2014 5:37 AM, ben wrote:
   Hello all,
   Just a heads up. I noted there is a lonely Datron / Wavetek 4920M 
   AC voltmeter for sale on ebay, starting at US$650 (ending in 1 day 
   !). I have little idea of its true working state or not (picture shows 
   it powered on).
   If fully working it would be a good buy for an AC voltmeter that 
   is, I reckon, better than an HP 3458A. Only drawback with these 
   models is the voltage input shell is always earthed, not floating. 
   I have two of these 4920M's already, not really tempted by a third. 
   I have a paper copies of operator, calibration, and service manual if 
   anyone interested.
  
   regards,   ben.
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Re: [volt-nuts] Datron 4920M, AC Voltmeter, for sale on ebay - 1 day left

[acbern]

charlie,

you can expand these tvcs by range resistors to work as higher voltage tvcs. if 
you do it right (rf-type setup) you can work up to a couple hundred khz with 
just minor additional error beyond its error in its orgininal voltage range. 
need to calibrate them however. using an attenuator is not a good idea, too 
unprecise. still tvcs are the most precise way to measure, if done right. 
pretty tme consuming though. but you need them e.g. to calibrate a 4920. 

adrian

 Gesendet: Sonntag, 31. August 2014 um 21:41 Uhr
 Von: Charles Black cbl...@centurytel.net
 An: Discussion of precise voltage measurement volt-nuts@febo.com
 Betreff: Re: [volt-nuts] Datron 4920M, AC Voltmeter, for sale on ebay - 1 day 
 left

 Hi Stephen,
 
 Thanks for the info on the 4920M. It might be that I should pass on this 
 but it is nice to know that it is probably working. If I don't have the 
 necessary items needed for calibration it might still be a good source 
 uncalibrated.
 
 I was hoping that the 4920 had better minimum voltage out steps than my 
 present Rigol 4062 for 3458a AC calibration. I have two EL 1400 0.25V 
 voltage thermal converters that I was trying to use in a test setup but 
 they had such a low voltage range that I was forced to use my ATV-60 
 attenuator. It all kind of worked but a 0.1 db minimum step  is a little 
 course for easy use. The Rigol also suffers from this malady.
 
 Charlie
 
 On 8/31/2014 1:06 PM, Stephen Grady wrote:
  Charlie,
 
 
  The Error Ur is an under-range error; you have to apply an input above 
  10% of the range before it will display a reading. The 4920's are a very 
  nice instrument. Their only problem is that they are all so old that they 
  are reaching the stage where some components are drifting excessively or 
  failing. I have come across 4920's that are drifting a little (more than 
  there spec) between cals (and yes they need to be cal'd annually), another 
  4920 I came across had an intermittent failure in one of its power supplies.
 
  Kind Regards,
 
  Stephen Grady
  Sydney Australia
 
  -Original Message-
  From: volt-nuts [mailto:volt-nuts-boun...@febo.com] On Behalf Of Charles 
  Black
  Sent: Monday, 1 September 2014 3:19 AM
  To: b...@veritechmeasurements.com.au; Discussion of precise voltage 
  measurement
  Subject: Re: [volt-nuts] Datron 4920M, AC Voltmeter, for sale on ebay - 1 
  day left
 
  Hi Ben,
 
  I am going to check this out today to find if it might be helpfull around 
  here for my AC calibration. It has an error message: Error Ur
  so some fixing is going to be needed. On the back it says it's got Option 
  80, whatever that is.
 
  Charlie
 
 
  On 8/31/2014 5:37 AM, ben wrote:
  Hello all,
  Just a heads up. I noted there is a lonely Datron / Wavetek 4920M AC
  voltmeter for sale on ebay, starting at US$650 (ending in 1 day !). I
  have little idea of its true working state or not (picture shows it 
  powered on).
  If fully working it would be a good buy for an AC voltmeter that is, I
  reckon, better than an HP 3458A. Only drawback with these models is
  the voltage input shell is always earthed, not floating. I have two of
  these 4920M's already, not really tempted by a third. I have a paper
  copies of operator, calibration, and service manual if anyone interested.
 
  regards,   ben.
  ___
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  https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
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Re: [volt-nuts] 732A and Prologix received

[acbern]

I do fully agree with you. this has become, to a big extent, an academic 
debate. it may be relavant if the resolution needs to be in the nv-range, such 
as working with josephson-elements. I guess nobody in this group here is.
to your question, yes, the 34420a and the 2182 nanovolt meters use pure copper 
contacts, and from time to time they should be cleaned with deoxit. I have not 
seen any issue with these connectors. would I use unplated (non-gold-surface) 
copper connectors if I had a choice. never. did i ever have an emf problem with 
my gold plated copper spades in use together with the 34420a and 3458a. no. so 
for me at least the answer is simple.
 

 Gesendet: Mittwoch, 27. August 2014 um 23:50 Uhr
 Von: Stan Katz stan.katz...@gmail.com
 An: Discussion of precise voltage measurement volt-nuts@febo.com
 Betreff: Re: [volt-nuts] 732A and Prologix received

 As a non-scholar in metrology, I tend to want to simplify the results of an
 academic debate to make the results of the debate useful to me. One thing
 is clear from my web search, copper alloyed with Tellurium, or Beryllium,
 still oxidizes, only at a slower rate. It appears that a big disadvantage
 of Beryllium oxide is its very hard, a useful industrial characteristic.
 Not a nice property in the metrology lab.
 
  Here goes:
 
 For the purists with lab grade metallurgical abrasives, polishing
 equipment, and oxide removal chemistry, only, copper, whether alloyed with
 Beryllium or Tellurium is all they want to see in their lead terminations,
 and they will try to procure only instruments with copper/copper alloy
 terminals. These purists will clean/deoxidize  all connections in a
 controlled atmosphere, and dry them in completely dry nitrogen, or other
 inert gas. The connections will then be used immediately during the
 measurement and the purists will have assured themselves that all
 instrument to lead connections are tight enough to be oxygen free.
 
 Can anyone mention any precision metrology instrumentation in current
 production with pure copper, or copper alloy connectors? I have a 38 year
 old Hp 740b, and yep, it's got Gold flashed connectors. This Gold flashing
 seems to be a tradition.
 
 The practical metrologist, will accept the fact that precision metrology
 instruments are meant to last many years, and the terminals supplied with
 these instruments must provide a stable thermal emf profile over time.
 Thus, they accept instruments that come with gold plated terminals. The
 Gold may need to be cleansed of debris, and degreased from time-to-time,
 but the procedure is much simpler, and not as time consuming as oxide
 removal.  The leads to these instruments are meant to be used day in, and
 day out, as well. Therefore, the leads also terminate in some form of gold
 plated connector. The practical metrologist is fastidious in controlling
 temperature, and air movement in the lab, to minimize thermal unbalance in
 his/her lash up.
 
 Is this a foolish simplification of the thermals debate, or can I feel
 vindicated using my homemade, gold plated lead terminations with my old
 740b, and 731b?
 
 
 On Wed, Aug 27, 2014 at 3:45 PM, M K m1k...@hotmail.com wrote:
 
  On 26/08/2014 16:05, Mike S wrote:
 
  After some more research, I think I've answered some of my own questions -
 
  Tellurium copper is used for binding posts, not because it has any
  special thermal or EMF mojo, but because it machines much better than pure
  copper. And, I suppose, because it sounds like it's extra special.
 
  The Seebeck coefficients (uV/C, relative to Cu) of some relevant
  materials:
  Cu 0.0
  Ag .2
  Au .5
  Yellow brass 1.5
  Phosphor bronze 2.0
  63/37 solder 3.0
  Sn 3.1
  Stainless steel 3.1
  Beryllium copper 5.0
  Fe -12.3
  Ni  22.3
  Te -49.25
 
  Based on the extreme Seebeck coefficient of pure tellurium vs. copper,
  I'd expect that there might be some coefficient between Cu and CuTe (0.5%
  Te), but I could find no reference. The relatively large number for CuBe is
  interesting, since that's a common material for banana plug springs, where
  one might expect the greatest temperature differential to occur in such a
  connection (between the thermal masses of the binding post/jack and the
  bulk of the banana plug). Heat has to flow a considerable distance through
  the springs, very much more than when it flows through a surface plating.
 
  The Pomona (Fluke) EM5295-48-0# uses CuBe (gold plated) for the spring
  contacts. It seems there might be an improvement to be had by using the
  older style pin plugs, where a solid pin was partially sliced into 4
  sections which were then spread apart a bit to create tension. That could
  eliminate relatively large thermocouples at a thermal gradient, and might
  also be expected to have less thermal resistance, allowing the connection
  to settle quicker.
 
  But maybe not - I'm still not clear on how plated conductors behave in
  this situation. For a high impedance voltage measurement 

Re: [volt-nuts] AC calibration

[acbern]

what nist means is that a precision meter is not considered a standard. you 
always measure against a true standard (732a, esi sr104...). nist does not mean 
that as part of doing equipment calibration a 3458a cannot be used as aid. also 
keep in mind nist has a different approach than a cal lab, for obvious reasons. 
a cal lab would do a transfer measurement using a 3458a and a voltage/current 
source, sure.

there are precision ratio transformers available from various vendors, they can 
be used for low frequency precision calibrations, up to 20khz only (if anybodys 
knows one specified above 20khz I am interested to hear). so they will help you 
only partially in calibrating even a low precision 5101.


 Gesendet: Mittwoch, 27. August 2014 um 07:08 Uhr
 Von: pa4...@gmail.com
 An: volt-nuts volt-nuts@febo.com
 Betreff: Re: [volt-nuts] AC calibration

 Thanks, I did not new NIST has so much interesting information on their site. 
 
 
 
 
 I read the following on their site :
 
 multirange instruments with up to eight decimal digits of adjustability, are 
 not considered by NIST to be standards 
 
 
 
 
 Does that mean a HP3458 ? Fluke in the Netherlands used a HP-3458 and a 732 
 to calibrate the Fluke 5101 that  I'm working on at this moment (it failed 
 calibration due to some hardware faults) 
 
 
 
 
 Everybody thanks for the information. Turns out, a friend has a GR 1455AH for 
 me, that is some kind a AC KV divider. 
 
 I will test if the output of my HP 3400 is usable to connect a DMM. I have 
 one I restored a few years ago. Besides that someone mentioned to look at the 
 LT-1088.  
 
 
 But that has to wait until I have some more time. I only repaired 
 calibration, percission gear and RF stuff  for my hobby, but, not planned, I 
 started to do this on a commercial base too. See my (non commercial) site 
 about my collection calibration and other gear and projects  www.pa4tim.nl .
 
 Today the 5101 goes back to the custommer but he brings 2 other instruments 
 in need of some TLC and a precheck before they are shipped to Fluke for 
 calibration.  And yesterday an other company asked if I want/can repair a GM 
 safety tester (a sort of megger on steroids) that died during calibration.  
 
 
 Fred
 

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Re: [volt-nuts] 732A and Prologix received

[acbern]

well, what you do is to measure the stability of the 3458a. 1ppm drift though 
sounds much as overall short term average variation if your temperature is 
stable and your 3458a is always on. probably the temp is not stable, and that 
is what you see, amongst potentially some other smaller drifts like emf. before 
every cycle you should do an acal dcv, if you still see 10uv +/- drifts that 
then seems too much. (one thing I need to add is that one of my 3458a, not yet 
modified to have lower reference temperature, has drifts when switched on and 
off. that is not so much the case with modified reference. but my assumption re 
the above is that your meter is always on, as I said) 
732a references et al do have small short term drifts, you can determine them 
with a josephson element (these guys told me), but the 732a is certainly very 
stable short term compared to a 3458a. my 732a e.g. has a drift of 0.2ppm per 
year.


 Gesendet: Mittwoch, 27. August 2014 um 14:36 Uhr
 Von: Randy Evans randyevans2...@gmail.com
 An: Discussion of precise voltage measurement volt-nuts@febo.com
 Betreff: Re: [volt-nuts] 732A and Prologix received

 I forgot to mention that I reduced the number of measurements to 100 per
 set since I wasn't seeing much difference in the variance between 100 and
 1000 measurements and the 1000 measurement per set takes too long.
 
 Randy
 
 
 On Wed, Aug 27, 2014 at 5:13 AM, Randy Evans randyevans2...@gmail.com
 wrote:
 
  I am doing multiple 100 measurements simply to characterize the stability
  of the 3458A and 732A units I just bought.  After about 10 measurement sets
  over 2 days I am seeing a variance of about .5 uV for the 10V output, or
  0.05 ppm.  However, the mean varies over a range of 10 uV, or 1 ppm.  Does
  that sound reasonable/
 
  Randy
 
 
  On Tue, Aug 26, 2014 at 5:41 PM, acb...@gmx.de wrote:
 
  hi randy,
 
  just for curiosity, why doing 100 measurements at nplc 1000. is this to
  sample a changing value?
  when i am doing 10 measurements from a stable signal at nplc 100 (only
  there many subsequent measuremnts with statistics make sense) I am already
  getting a stanard deviation below 0.1ppm.
  in a 30 minute test cycle, i would also be concerned about drifts (acal)
  unless the amb. temperature is really very stable (half a degree already
  adds about 0.25ppm at 10v)
 
  thanks
 
 
 
 
   Gesendet: Dienstag, 26. August 2014 um 04:23 Uhr
   Von: Randy Evans randyevans2...@gmail.com
   An: Discussion of precise voltage measurement volt-nuts@febo.com
   Betreff: Re: [volt-nuts] 732A and Prologix received
  
   Is there any way to tell when the function key routine is complete?  In
  the
   case of taking multiple readings using the DEFKEY and MATH function, I
   don't see any indication when the routine is complete.  In one
  particular
   case, I am taking a 100 readings with NLPC set for 1000 so its a long
  while
   before it's complete, but i have to guess when it's done.
  
   Thanks,
  
   Randy
  
  
   On Sun, Aug 24, 2014 at 6:04 PM, Randy Evans randyevans2...@gmail.com
   wrote:
  
Bill,
   
I am trying to figure out the MATH function without much success.  I
  input
the sequence you said (I looked up the instructions to understand
  what you
did - seems logical), BLUE DEFKEY BLUE F1 MATH 14;NRDGS 40;TRIG
  4;TRIG; and
it shows up on the display when I input BLUE F1.  I hit ENTER and it
  takes
the 40 measurements and the MATH symbol shows on the display during
  the
measurements.  After the SMPL symbol no longer blinks I hit MATH 2
  and I
get a MATH ERR symbol on the display.  I tried it a couple of times
  and the
same result so I am doing something wrong.  Is there a better source
  for
explaining how to do front panel masurements than the User Guide,
  which
seems oriented at programming automatic rather than manual
  measurements.
   
Randy
   
   
   
On Sun, Aug 24, 2014 at 4:46 PM, Bill Gold wpgold3...@att.net
  wrote:
   
Randy:
   
The MATH function is accessible from the keypad.  I don't have
  an IEEE
interface right now that works.  You can also program the numeric
  keypad
keys to have preprogrammed functions.  DEFKEY
   
I have made my own low thermal measurement leads from Pomona
  #4892
banana plugs and Belden #9272 wire.  Why 9272, because it was handy
  at the
time.  It is tin plated copper, shielded twisted pair 20 ga.  I have
  plans
to do custom cables with 16 ga. bare copper wire that I will twist
  and
then
put a braided shield over it.  I simply cannot find what I want so I
  will
build my own cable.  I have done something like this before and it
  worked
fine.  When I get a round toit.
   
I have 6 ea. Pomona 1756-48 spade lug low thermal leads that I
  have
used
in the past to verify my homemade low thermal leads as described
  above.
Frankly I cannot see any difference between using the 1756 cables
  and 

Re: [volt-nuts] 732A and Prologix received

[acbern]

hi randy,
the specified drift of the 3458a over your 38.1 to 40.3 (about 1k) is 1ppm +/- 
allone in the 10v range. thats 10uv. in other ranges its worse.
unless your 732a is very bad (very unlikely), you measure mostly the 3458a 
temp. drift. 1000nplc and 100 readings average do not make sense in that 
context. if your goal is to be at 0.01ppm additional gain error by using the 
nplc1000, you need to be sure your temp related drift is even below that. 
0.01ppm of temp drift equates 20mk temp stability! you see that all this does 
not make much sense.


adrian


 Gesendet: Mittwoch, 27. August 2014 um 15:37 Uhr
 Von: Randy Evans randyevans2...@gmail.com
 An: Discussion of precise voltage measurement volt-nuts@febo.com
 Betreff: Re: [volt-nuts] 732A and Prologix received

 The HP3458A and the Fluke 732A are on continuously and I do an ACAL at
 least every few hours, or when the room temperature changes by more than 1
 degree C. The total range of measurements is 10uV so the drift is +/-5uV,
 or 0.5 ppm.  The room temperature is not particularly stable and varies
 over a 3C range.  The internal temp of the 3458 varies from 38.1 to 40.3
 degrees C over the set of measurements.  The 732A thermistor resistance
 measures from 3.6677 Kohms to  3.6686 Kohms.  I am using copper wires
 between the 3458A and the 752A to minimize thermals.  At the moment I have
 no way to tell which unit is drifting the most.
 
 Randy
 
 
 On Wed, Aug 27, 2014 at 6:41 AM, acb...@gmx.de wrote:
 
  well, what you do is to measure the stability of the 3458a. 1ppm drift
  though sounds much as overall short term average variation if your
  temperature is stable and your 3458a is always on. probably the temp is not
  stable, and that is what you see, amongst potentially some other smaller
  drifts like emf. before every cycle you should do an acal dcv, if you still
  see 10uv +/- drifts that then seems too much. (one thing I need to add is
  that one of my 3458a, not yet modified to have lower reference temperature,
  has drifts when switched on and off. that is not so much the case with
  modified reference. but my assumption re the above is that your meter is
  always on, as I said)
  732a references et al do have small short term drifts, you can determine
  them with a josephson element (these guys told me), but the 732a is
  certainly very stable short term compared to a 3458a. my 732a e.g. has a
  drift of 0.2ppm per year.
 
 
   Gesendet: Mittwoch, 27. August 2014 um 14:36 Uhr
   Von: Randy Evans randyevans2...@gmail.com
   An: Discussion of precise voltage measurement volt-nuts@febo.com
   Betreff: Re: [volt-nuts] 732A and Prologix received
  
   I forgot to mention that I reduced the number of measurements to 100 per
   set since I wasn't seeing much difference in the variance between 100 and
   1000 measurements and the 1000 measurement per set takes too long.
  
   Randy
  
  
   On Wed, Aug 27, 2014 at 5:13 AM, Randy Evans randyevans2...@gmail.com
   wrote:
  
I am doing multiple 100 measurements simply to characterize the
  stability
of the 3458A and 732A units I just bought.  After about 10 measurement
  sets
over 2 days I am seeing a variance of about .5 uV for the 10V output,
  or
0.05 ppm.  However, the mean varies over a range of 10 uV, or 1 ppm.
  Does
that sound reasonable/
   
Randy
   
   
On Tue, Aug 26, 2014 at 5:41 PM, acb...@gmx.de wrote:
   
hi randy,
   
just for curiosity, why doing 100 measurements at nplc 1000. is this
  to
sample a changing value?
when i am doing 10 measurements from a stable signal at nplc 100 (only
there many subsequent measuremnts with statistics make sense) I am
  already
getting a stanard deviation below 0.1ppm.
in a 30 minute test cycle, i would also be concerned about drifts
  (acal)
unless the amb. temperature is really very stable (half a degree
  already
adds about 0.25ppm at 10v)
   
thanks
   
   
   
   
 Gesendet: Dienstag, 26. August 2014 um 04:23 Uhr
 Von: Randy Evans randyevans2...@gmail.com
 An: Discussion of precise voltage measurement volt-nuts@febo.com
  
 Betreff: Re: [volt-nuts] 732A and Prologix received

 Is there any way to tell when the function key routine is
  complete?  In
the
 case of taking multiple readings using the DEFKEY and MATH
  function, I
 don't see any indication when the routine is complete.  In one
particular
 case, I am taking a 100 readings with NLPC set for 1000 so its a
  long
while
 before it's complete, but i have to guess when it's done.

 Thanks,

 Randy


 On Sun, Aug 24, 2014 at 6:04 PM, Randy Evans 
  randyevans2...@gmail.com
 wrote:

  Bill,
 
  I am trying to figure out the MATH function without much
  success.  I
input
  the sequence you said (I looked up the instructions to understand
what you
  did - seems logical), BLUE DEFKEY BLUE F1 MATH 14;NRDGS 

Re: [volt-nuts] AC calibration

[acbern]

Dave,

the title is: 
Thermal Voltage Converters and Comparator for Very Accurate AC Voltage 
Measurements
by E.S.Williams.

Adrian


 Gesendet: Montag, 25. August 2014 um 19:32 Uhr
 Von: Dave M dgmin...@mediacombb.net
 An: Discussion of precise voltage measurement volt-nuts@febo.com
 Betreff: Re: [volt-nuts] AC calibration

 Adrian,
 Do you have a link or title for the NIST paper that you mentioned?
 
 Dave M
 
 
 acb...@gmx.de wrote:
  fred,
  generally you raise a good point, I had the same issue of calibrating
  an ac voltage to a high level of accuracy. you need this e.g. to
  validate the self.cal of a 3458a or other precison stuff like the
  8506a0.   
  
  what i would recommend to do if you want to keep costs down is:
  in a nutshell, get a thermal converter in the lowest range you need
  and a second one on range above. build a set of resistor range
  extenders (rf type with appropriate connectors and housings) to
  expand the range to where you need to be max. get one of the thermal
  converter calibrated (the higher one usually, and you need to havr 
  good cal lab, should be 10ppm accuracy) and use it to calibrate the
  rest. generally, up to 20khz, the accuracy is some 20 ppm anyway for
  thermal converters! at higher frequencies, due to reflections and
  stray capacitance/inductance influences, the accuracy decreases. the
  resistor range extenders though, if build up correctly, only have a
  few ppm impact (there is a paper from nist on that, but this is only
  typical). you can calibrate all converters to the one you got
  externally calibrated. do some research in the web, when you do the
  calibration, you need to determine the so-called constant N. then do
  an ac, dc+, ac, dc-, ac measurement between the the two and establish
  the deviation, also establish the error propagation. the end result
  will be a set of highly precise (low inaccuracies9 thermal converters
  good enough to calibrate a 3458a an better devices. if you want to
  spend the money, you could also buy a set of converters/range
  resistors (with/without a 540), that typically is a few k altogether,
  while a single device sometimes is available for below 100 bucks. you
  need to have a stable 7.5 digit nanovoltmeter though for the
  measurements of the tvcs (34420a or 2182 typically ) and precision
  (stable) dc and ac sources. but in the end, all you need is a single
  calibrated thermal converter.
  
  adrian
  
  
  
  Gesendet: Montag, 25. August 2014 um 18:38 Uhr
  Von: Dave M dgmin...@mediacombb.net
  An: Discussion of precise voltage measurement volt-nuts@febo.com
  Betreff: Re: [volt-nuts] AC calibration
  
  Well, you sort of answered your own question.  The equipment is
  called a Thermal Transfer Standard, but instead of thermistors, it
  uses a thermocouple.  Look at the manual for the Fluke 540B
  (http://bama.edebris.com/manuals/fluke/540b/) and you'll see how
  it's done. Basically, the AC source is input into the transfer
  standard, and the standard's internal reference voltage is adjusted
  for a null on the galvanometer.  Leaving the reference voltage
  setting alone, a DC voltage is input into the unit, and the DC
  source is adjusted for a null on the galvanometer.  At that point,
  the AC voltage source is equal to that of the DC voltage source.
  
  Ther are thermocouple-type thermal converters used for RF voltage
  measurements with the transfer standard.  They aren't cheap, and you
  have to have a converter for each range of voltages that you need to
  measure.  The thermal converters used with this type of transfer
  standard isn't great (50 MHz or so typical), but their accuracy far
  surpasses that of the thermistor type sensors.
  
  There are other brands and models of thermal transfer standards, but
  I have a Fluke model 540 and a few thermal converters.  That's why I
  referred you to the manual for it.
  
  Cheers,
  Dave M
  
  
  pa4...@gmail.com wrote:
  Is there a way to link an AC voltage to a DC source for compare. I
  can check my calibrators (like a Fluke 332, 760 , 731 and a Philips)
  against standardcells. But for AC I can not do that. I have two
  AC+DC TRMS 7,5 digit meters but the last calibration was 2 years
  ago. 
  
  My idea is in theory simple. It is based on the thermal converters
  used in RF powermeters. Two resistors, two high resolution
  temperature meters. AC on the first en DC on the second. If both are
  the same temperature the AC voltage is the same as the DC voltage.
  But I'm sure some people here have done this in the past. I would
  like to use it for 50 to 100 kHz (or less) and something like for
  1V, 10V and 100V (and use several resistors/heaters.)
  
  Or mabey there is an other way to convert AC (for RF it can be done
  with lightbubs but I never tryed that)  I do not mind if it is slow
  etc, I like this sort of experiments. You can learn a lot from it.
  
  Fred, pa4tim
  
  
  

Re: [volt-nuts] 732A and Prologix received

[acbern]

hi randy,

just for curiosity, why doing 100 measurements at nplc 1000. is this to sample 
a changing value?
when i am doing 10 measurements from a stable signal at nplc 100 (only there 
many subsequent measuremnts with statistics make sense) I am already getting a 
stanard deviation below 0.1ppm.
in a 30 minute test cycle, i would also be concerned about drifts (acal) unless 
the amb. temperature is really very stable (half a degree already adds about 
0.25ppm at 10v)

thanks




 Gesendet: Dienstag, 26. August 2014 um 04:23 Uhr
 Von: Randy Evans randyevans2...@gmail.com
 An: Discussion of precise voltage measurement volt-nuts@febo.com
 Betreff: Re: [volt-nuts] 732A and Prologix received

 Is there any way to tell when the function key routine is complete?  In the
 case of taking multiple readings using the DEFKEY and MATH function, I
 don't see any indication when the routine is complete.  In one particular
 case, I am taking a 100 readings with NLPC set for 1000 so its a long while
 before it's complete, but i have to guess when it's done.
 
 Thanks,
 
 Randy
 
 
 On Sun, Aug 24, 2014 at 6:04 PM, Randy Evans randyevans2...@gmail.com
 wrote:
 
  Bill,
 
  I am trying to figure out the MATH function without much success.  I input
  the sequence you said (I looked up the instructions to understand what you
  did - seems logical), BLUE DEFKEY BLUE F1 MATH 14;NRDGS 40;TRIG 4;TRIG; and
  it shows up on the display when I input BLUE F1.  I hit ENTER and it takes
  the 40 measurements and the MATH symbol shows on the display during the
  measurements.  After the SMPL symbol no longer blinks I hit MATH 2 and I
  get a MATH ERR symbol on the display.  I tried it a couple of times and the
  same result so I am doing something wrong.  Is there a better source for
  explaining how to do front panel masurements than the User Guide, which
  seems oriented at programming automatic rather than manual measurements.
 
  Randy
 
 
 
  On Sun, Aug 24, 2014 at 4:46 PM, Bill Gold wpgold3...@att.net wrote:
 
  Randy:
 
  The MATH function is accessible from the keypad.  I don't have an IEEE
  interface right now that works.  You can also program the numeric keypad
  keys to have preprogrammed functions.  DEFKEY
 
  I have made my own low thermal measurement leads from Pomona #4892
  banana plugs and Belden #9272 wire.  Why 9272, because it was handy at the
  time.  It is tin plated copper, shielded twisted pair 20 ga.  I have plans
  to do custom cables with 16 ga. bare copper wire that I will twist and
  then
  put a braided shield over it.  I simply cannot find what I want so I will
  build my own cable.  I have done something like this before and it worked
  fine.  When I get a round toit.
 
  I have 6 ea. Pomona 1756-48 spade lug low thermal leads that I have
  used
  in the past to verify my homemade low thermal leads as described above.
  Frankly I cannot see any difference between using the 1756 cables and my
  homemade cables once I give them a few minutes for the thermals to go
  away.
  As far as I can tell and measure the differences, if any, are below 0.1
  ppm
  at 10 volts.
 
  Since the 10 volt, 1.0 volt and 1.018 volt outputs on the 732A are all
  adjustable you may be seeing a misadjusted 1 volt from the 732A.  As far
  as
  the instability of the readings it is hard to determine which is causing
  the
  problem.  I have programed (DEFKEY) a numeric keypad key #1 with the
  following code.  MATH 14;NRDGS 40;TRIG 4;TRIG ;   So what this does is
  set
  the MATH to Statistics (store high reading/low reading/ and mean of the
  readings) in the registers, the number of readings to 40, the trigger to
  hold (which keeps the meter from triggering until I press ENTER and
  then
  trigger the sequence of 40 readings when I push the ENTER button.  You
  can
  do all of this manually from the keypads but since I use this sequence a
  lot
  I have preprogrammed it.  This is after I set digits to 8 and PLC to
  100.
  Once those 40 readings are finished then you can access the various MATH
  statistic registers, using the menu, by entering MATH and then a 2 for
  low, a 4 for mean, and 13 for high.  Of course you could do all of this
  through the IEEE also.  The 3458A has a very rich set of measurement
  commands.  I am still learning all of them.  It depends upon what I am
  trying to accomplish.
 
  Since the 1.018 and 1.0 volt outputs are passive and derived from
  resistive dividers from the 10 volt, I don't see how they could contribute
  to the varying readings you are measuring.  I think I would put a short on
  the input of the 3458A and manually set the range to 1 volt and then
  observe
  the variations that way without the 732A involved.  When I do this I see a
  variation from low reading to high reading of 0.125 uVolts and then
  another
  40 I get 0.155 uVolts.  This is without the GUARD connected to the low
  side
  of the measurment terminals, GUARD connected doesn't seem to affect 

Re: [volt-nuts] 732A and Prologix received

[acbern]

I have used the pomona spades, mainly to interface the low emf pomona banana 
cables to binding posts. I have stopped this, reasons being, they are large and 
worse, that the pomona spring loaded insulation tube that covers the banana 
plug conductor uses such a strong spring that slowly the plug works its way out 
of the spade. this btw also happend to me when I used the pomona low emf 
binding posts together with the pomona low emf banana cables. overall I m not 
happy with these. 
so, due to lack of options, I changed to self-made twisted shielded pair of 
high grade teflon/kapton silver plated copper cable with gold plated copper 
spades (crimped). I use them not only with the 3458a but also with nanovolt 
meters. these have higher resolution and accuracy in low level measurements 
than the 3458a. emf voltages were never an issue with these cables if properly 
used. I have posted some results doing 34420a stabilty measurements on the pmel 
forum, and the results are convincing (purpose was actually not to test the 
cables but the stability of the 34420a, but the emf issue is a part of this of 
course. we use the 34420a to do low voltage precision measurements on thermal 
converters where the full scale signal sometimes is 1mV). 
that btw also relates to don's statements below, I do not concurr with his 
comments about copper telurium as cable and spade material and so on. this 
material, as stated here many times, is used because it is machinable, for 
copper spades one would not use it. the 34420a factory cable uses copper cable 
and copper spades, not telurium-copper. if there was a problem, it would be 
worse with the 34420a than with the 3458a because of its low level ranges. and 
again, I have not seen any problems in a chain of (output to input):
1.copper-tellurium post from e.g. 8 digit calibrator
2.crimped copper spade, gold plated
3.silver plated tsp copper cable
4a.crimped copper spade to copper-tellurium post or 
4b.soldered copper connector(34420)
my consistent results over more than a year using them.



 Gesendet: Montag, 25. August 2014 um 06:33 Uhr
 Von: Orin Eman orin.e...@gmail.com
 An: Discussion of precise voltage measurement volt-nuts@febo.com
 Betreff: Re: [volt-nuts] 732A and Prologix received

 On Sun, Aug 24, 2014 at 1:46 PM, Don@True-Cal truecalservi...@gmail.com
 wrote:
 
  Randy  all,
 
  You have correctly concluded that some (maybe not all) of your measurement
  problem is thermal EMF being added or subtracted in series within your
  measurement interconnect. This thermal EMF is generated at the junction of
  dissimilar metals when accompanied with thermal gradients between the test
  lead and device terminals. You have to eliminate both the dissimilarity of
  the metal junctions as well as minimize the thermal differences. The
  terminals of the 3458A as well as the 732A are Beryllium Copper so you want
  to use the same test lead terminals. Forget the typical Tin plated lugs or
  even Gold plated as both are not Beryllium Copper and constitute dissimilar
  metals. The best solution (as usually the most expensive) is to use a set
  of
  Fluke 5440A-7005 (48) cables. I also have just as good results using the
  much more flexible Pomona 11174A (lugs end always stay connected to the
  732A) or 11058A with more convenient shielded banana plugs. The Fluke cable
  has the added Guard built in but be sure to also use a Guard lead with the
  Pomona cabled. The Guard lead does not need to be low thermal EMF. DIY
  cables is usually not a good idea because the lead wire to terminal also
  constitutes just as critical of junction. The above cables use Tellurium
  Copper wire which is usually hard to find and hard to crimp properly and
  NEVER solder.
 
 
 
 11058A and 11174A are discontinued at Keysight.  However, Pomona 5295 spade
 to banana cables are available (5295-36 at Mouser et al) and claim that
 they are designed to minimize thermal EMFs.  Datasheet is here:
 http://www.mouser.com/ds/2/159/d5295_1_01-51722.pdf  Any comments on these
 as an alternative?
 
 Orin.
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Re: [volt-nuts] 732A and Prologix received

[acbern]

well, your last point is the issue, how can you have a temperature difference 
within a few microns of material in said connections. theory is one thing, but 
in reality it does not happen due to the givens of the setup.
therefore in practice it is irrelevant if the wire is silver or gold plated or 
pure copper. otherwise the gold plated spades and tellurium copper posts from 
pomona and others would be nonsense. and other than the mysterious fluke wire I 
have never seen a tellurium-copper wire from any wire manufacturer.


 Gesendet: Montag, 25. August 2014 um 17:02 Uhr
 Von: Don@True-Cal truecalservi...@gmail.com
 An: 'Discussion of precise voltage measurement' volt-nuts@febo.com
 Betreff: Re: [volt-nuts] 732A and Prologix received

 Tellurium Copper is usually not used for a device's terminal posts but used 
 as the lead wire due, as you say, for the malleability to crimp well and 
 flexibility. The point I was making is to use the same interconnect test lead 
 material throughout as the DUT terminal posts. The 3458A and the 732A both 
 use Beryllium Copper alloy making that type interconnect lug or plug the best 
 choice to minimize the dissimilar metal EMF or Seebeck voltage. The 34420A 
 uses pure copper rather than an alloy terminal and for the same reason, 
 minimal Seebeck voltage is realized with a pure copper interconnect. Any type 
 of Silver or Gold plating on the terminal or wire will introduce the 
 undesirable  dissimilar metal properties, both at the plating junction and at 
 the plating metal to DUT terminal.
 
 The NI website had this chart that quantifies the Seebeck voltage best:
 When two, dissimilar metals are joined a voltage is created. This voltage is 
 known as the thermal electromotive force (EMF) or the Seebeck voltage. The 
 Seebeck voltage is dependent on the temperature of the junction and the 
 composition of the metals joined. The specific metal-to-metal junctions 
 result in specific temperature coefficients (µV/°C), also known as Seebeck 
 coefficients. The following table lists the most common metals and their 
 respective Seebeck coefficients.
 
 Junction  µV/°C
 Copper-Copper 0.3
 Copper-Gold   0.5
 Copper-Silver 0.5
 Copper-Brass  3
 Copper-Nickel 10
 Copper-Lead-Tin Solder 1-3
 Copper-Aluminum   5
 Copper-Kovar  40
 Copper-Copper Oxide   500
 
 Granted, Gold and Silver are the next best choice, and is certainly why they 
 are satisfactory, but using either warrants a more critical temperature 
 gradient issue. If your measurements were satisfactorily convincing, than you 
 probably had no appreciable junction temperature differences. 
 
 Don Johnson
 
 -Original Message-
 From: volt-nuts [mailto:volt-nuts-boun...@febo.com] On Behalf Of acb...@gmx.de
 Sent: Monday, August 25, 2014 5:37 AM
 To: Discussion of precise voltage measurement
 Subject: Re: [volt-nuts] 732A and Prologix received
 
 I have used the pomona spades, mainly to interface the low emf pomona banana 
 cables to binding posts. I have stopped this, reasons being, they are large 
 and worse, that the pomona spring loaded insulation tube that covers the 
 banana plug conductor uses such a strong spring that slowly the plug works 
 its way out of the spade. this btw also happend to me when I used the pomona 
 low emf binding posts together with the pomona low emf banana cables. overall 
 I m not happy with these. 
 so, due to lack of options, I changed to self-made twisted shielded pair of 
 high grade teflon/kapton silver plated copper cable with gold plated copper 
 spades (crimped). I use them not only with the 3458a but also with nanovolt 
 meters. these have higher resolution and accuracy in low level measurements 
 than the 3458a. emf voltages were never an issue with these cables if 
 properly used. I have posted some results doing 34420a stabilty measurements 
 on the pmel forum, and the results are convincing (purpose was actually not 
 to test the cables but the stability of the 34420a, but the emf issue is a 
 part of this of course. we use the 34420a to do low voltage precision 
 measurements on thermal converters where the full scale signal sometimes is 
 1mV). 
 that btw also relates to don's statements below, I do not concurr with his 
 comments about copper telurium as cable and spade material and so on. this 
 material, as stated here many times, is used because it is machinable, for 
 copper spades one would not use it. the 34420a factory cable uses copper 
 cable and copper spades, not telurium-copper. if there was a problem, it 
 would be worse with the 34420a than with the 3458a because of its low level 
 ranges. and again, I have not seen any problems in a chain of (output to 
 input):
 1.copper-tellurium post from e.g. 8 digit calibrator 2.crimped copper spade, 
 gold plated 3.silver plated tsp copper cable 4a.crimped copper spade to 
 copper-tellurium post or 4b.soldered copper connector(34420) my consistent 
 

Re: [volt-nuts] AC calibration

[acbern]

fred,
generally you raise a good point, I had the same issue of calibrating an ac 
voltage to a high level of accuracy. you need this e.g. to validate the 
self.cal of a 3458a or other precison stuff like the 8506a0.

what i would recommend to do if you want to keep costs down is: 
in a nutshell, get a thermal converter in the lowest range you need and a 
second one on range above. build a set of resistor range extenders (rf type 
with appropriate connectors and housings) to expand the range to where you need 
to be max. get one of the thermal converter calibrated (the higher one usually, 
and you need to havr  good cal lab, should be 10ppm accuracy) and use it to 
calibrate the rest. generally, up to 20khz, the accuracy is some 20 ppm anyway 
for thermal converters! at higher frequencies, due to reflections and stray 
capacitance/inductance influences, the accuracy decreases. the resistor range 
extenders though, if build up correctly, only have a few ppm impact (there is a 
paper from nist on that, but this is only typical). you can calibrate all 
converters to the one you got externally calibrated. do some research in the 
web, when you do the calibration, you need to determine the so-called constant 
N. then do an ac, dc+, ac, dc-, ac measurement between the the two and 
establish the deviation, also establish the error propagation. the end result 
will be a set of highly precise (low inaccuracies9 thermal converters good 
enough to calibrate a 3458a an better devices. if you want to spend the money, 
you could also buy a set of converters/range resistors (with/without a 540), 
that typically is a few k altogether, while a single device sometimes is 
available for below 100 bucks. you need to have a stable 7.5 digit 
nanovoltmeter though for the measurements of the tvcs (34420a or 2182 typically 
) and precision (stable) dc and ac sources. but in the end, all you need is a 
single calibrated thermal converter.

adrian



 Gesendet: Montag, 25. August 2014 um 18:38 Uhr
 Von: Dave M dgmin...@mediacombb.net
 An: Discussion of precise voltage measurement volt-nuts@febo.com
 Betreff: Re: [volt-nuts] AC calibration

 Well, you sort of answered your own question.  The equipment is called a 
 Thermal Transfer Standard, but instead of thermistors, it uses a 
 thermocouple.  Look at the manual for the Fluke 540B 
 (http://bama.edebris.com/manuals/fluke/540b/) and you'll see how it's done.
 Basically, the AC source is input into the transfer standard, and the 
 standard's internal reference voltage is adjusted for a null on the 
 galvanometer.  Leaving the reference voltage setting alone, a DC voltage is 
 input into the unit, and the DC source is adjusted for a null on the 
 galvanometer.  At that point, the AC voltage source is equal to that of the 
 DC voltage source.
 
 Ther are thermocouple-type thermal converters used for RF voltage 
 measurements with the transfer standard.  They aren't cheap, and you have to 
 have a converter for each range of voltages that you need to measure.  The 
 thermal converters used with this type of transfer standard isn't great (50 
 MHz or so typical), but their accuracy far surpasses that of the thermistor 
 type sensors.
 
 There are other brands and models of thermal transfer standards, but I have 
 a Fluke model 540 and a few thermal converters.  That's why I referred you 
 to the manual for it.
 
 Cheers,
 Dave M
 
 
 pa4...@gmail.com wrote:
  Is there a way to link an AC voltage to a DC source for compare. I
  can check my calibrators (like a Fluke 332, 760 , 731 and a Philips)
  against standardcells. But for AC I can not do that. I have two AC+DC
  TRMS 7,5 digit meters but the last calibration was 2 years ago.
 
  My idea is in theory simple. It is based on the thermal converters
  used in RF powermeters. Two resistors, two high resolution
  temperature meters. AC on the first en DC on the second. If both are
  the same temperature the AC voltage is the same as the DC voltage.
  But I'm sure some people here have done this in the past. I would
  like to use it for 50 to 100 kHz (or less) and something like for 1V,
  10V and 100V (and use several resistors/heaters.)
 
  Or mabey there is an other way to convert AC (for RF it can be done
  with lightbubs but I never tryed that)  I do not mind if it is slow
  etc, I like this sort of experiments. You can learn a lot from it.
 
  Fred, pa4tim 
 
 
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Re: [volt-nuts] 732A and Prologix received

[acbern]

Randy,

I have replaced batteries in two units so far, which I bought on ebay (6V) and 
they fitted absolutelly perfect, no need to rework an metal and there was o 
isue with shortages. So there certainly are standard 6V batteries that fit 
without mods. I always try to keep things in original config, if possible.
Also, you do not want to adjust the 732a trimmers. It only gets unstable, if 
you are unlucky. I discussed this with some cal labs, same answer. What you 
could do is to adjust the jumper settings for coarse adjustment, if need be.
Adrian



 Gesendet: Samstag, 23. August 2014 um 04:03 Uhr
 Von: Randy Evans randyevans2...@gmail.com
 An: Discussion of precise voltage measurement volt-nuts@febo.com
 Betreff: Re: [volt-nuts] 732A and Prologix received

 Todd,
 
 Thanks for the info.  I have several Panasonic 12V 7 AH batteries that I
 keep topped off and they have very low current draw (~2 to 3 mA at 13.5
 VDC) when charged and at their float voltage, so I am pretty sure they are
 in good condition.  I will look at getting those in the units after I
 ascertain the condition of the 732.
 
 So now I have a what appears to be a functioning 3458A and a 732A but they
 slightly disagree.  I am like the man with two watches that disagree on the
 time  - which is correct?  For the moment, i am only concerned with
 stability.  The need for absolute accuracy will come later.
 
 Randy
 
 
 On Fri, Aug 22, 2014 at 8:06 PM, Todd Micallef tmical...@gmail.com wrote:
 
  Randy,
 
  You have two possible choices. It can be configured with 4 x 6v 4Ah
  batteries or 2 x 12v 7Ah batteries. Hopefully the previous owner has
  modified the battery pack already. A couple of mine needed a nibbler tool
  to remove enough of the aluminum cover that fits over the tops of the
  batteries. The original cover will short out to the battery tabs regardless
  of the battery configuration if this is not done.
 
  You can find larger capacity batteries that will give you slightly more
  battery life. I lost a couple sets of mail-order batteries after a few
  extended outages. I would recommend going with locally bought batteries
  instead of the cheaper mail order. My local Batteries Plus will typically
  have some warranty if I remember correctly. Moving forward I will only use
  2 12v batteries and pre-charge them on a battery charger to equalize them
  before putting them in the 732A. I think the cheap batteries did not
  discharge equally, and would not recover when power was applied.
 
  Inspect the back plane for damaged traces and look at the capacitors. I had
  a few that looked questionable. So far, I have replaced all the big caps on
  the pre-regulator and regulator boards. My feeling is that once these go
  online, they should run as long as possible between repairs.
 
  The battery charger circuit may need adjusting. I tweaked mine and it
  seemed to work fine.
 
  Todd
 
 
  On Fri, Aug 22, 2014 at 10:42 PM, Randy Evans randyevans2...@gmail.com
  wrote:
 
   I received my Fluke 732A today.  Just powered it up but it needs new
   batteries.  Any suggestions for sources (I haven't opened up the unit
  yet -
   I want to make sure it works before doing that).  Also received the
   ProLogix USB-GPIB adapter.  I plan on using Mark Sims' CAL ran data
  dumper
   program to get the CAL data from my 3458A.  Should be a busy weekend.
  
   Randy
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Re: [volt-nuts] 732A drift

[acbern]

Randy,

that is strange. two things come in mind that might be worth checking. first, 
is the mains frequency setting of the 3458a set to 60Hz (I assume you are in 
the US)? this is important to suppress mains ac disturbing the measurement.
secondly, have you connected guard? tsp cables would be best to use.

a general statment re. the 1V and 1.18V. they are much less stable than the 
10V. My 732A e.g. has a drift of 0.2ppm/a. So I use a kelvin-varley divider if 
I need 1V. this is self calibrating, so you have maybe 0.1ppm worse accuracy. 
you could also use the 3458a linearity to re-characterize the 1v with reference 
to the 10V. That also gives you good accuracy. Also, I only have the 10V cal'ed 
on a regular basis to below 0.5ppm accuracy, that costs much less than haveing 
all three voltages cal'ed, which would not add any benefit anyway.

Adrian

 Gesendet: Samstag, 23. August 2014 um 05:16 Uhr
 Von: Randy Evans randyevans2...@gmail.com
 An: volt-nuts@febo.com volt-nuts@febo.com
 Betreff: [volt-nuts] 732A drift

 I hope someone can help with a strange anomaly on either my 3458A or the
 732A.  The 732A 10V output as measured on my 3458A seems relatively stable
 over time (it bounces around about +/-1 uV but is it the 732 or the 3458?).
  However, the 1.000 VDC output drifts downward at a rate around 1-2 uV per
 second as soon as I plug the 3458A into the 732 output. If I remove the
 3458A and connect it back up after a few 10s of seconds, the reading goes
 back to what it started at and then drifts downward again.  The 1.018V
 output also drifts downward but at a much slower rate and not as much.  Now
 the question is: is it the 732 or the 3458A?  I tried to see it on my
 Agilent 34401A DMM but it really doesn't have the resolution, but I do seem
 to see it on the 1.000VDC output.  If it is the 732A, what would cause it
 to drift downward like that?  Since the 3458A has an input impedance of
 10Gohm on the 1 and 10 V ranges, I wouldn't think the 732 would even see
 the difference of whether the 3458A is connected of not, but it clearly
 makes a difference as to how long its connected and how long it's been
 disconnected.
 
 Any one have any conjectures?
 
 Also, what will turn on the In Cal light?  What does it mean if it
 doesn't come on?
 
 Thanks,
 
 Randy
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Re: [volt-nuts] What's All This Low Thermal EMF Test Lead Stuff?

[acbern]

if you buy a voltage source that is cal'ed to 6ppm you do not end uop with a 
factor of 10 (60ppm). the fatcor of 10 is often used to be on the safe side, 
but in high percision cals 10 is not achievable anyways. some mil standards 
call for 4, but what you should do is to analyze the error propagation and then 
determine the likely final uncertainty (you would do this with a certain 
confidence level, say 95% which is usual). so you would look at the different 
contributors (temo variation, aging since call'ed, error due to emf voltage and 
so on). you would add these up by the rss (root sum square) method.
there is a lot of literature out there for this, also free on the net, and it 
would not be possible to describe the details here, but I would suggest to do 
this, as the real error will be much better I am sure.



 Gesendet: Mittwoch, 20. August 2014 um 03:03 Uhr
 Von: Stan Katz stan.katz...@gmail.com
 An: Discussion of precise voltage measurement volt-nuts@febo.com
 Betreff: Re: [volt-nuts] What's All This Low Thermal EMF Test Lead Stuff?

 If you reserve those pure copper bananas strictly for infrequent cal. of
 something like an HP3458, or other transfer standards in your lab,  they
 may be good for some years.
 
 I envision the beer nuts  to be a rather relaxed group of individuals,
 who are perfectly satisfied to know the alcohol content of their favorite
 brew to no better than +/- 60ppm ;-)
 
 Why +/- 60ppm?  A selfish reason. I plan on bringing home a beer-nut-NIST
 volt for my Fluke 731B using one of these standards
 http://www.ebay.com/itm/10-VOLT-DC-Precision-Voltage-Reference-Standard-Nulled-to-Fluke-732A-732B-/261499015291?pt=LH_DefaultDomain_0hash=item3ce28e507b
 
 They're only good to 6ppm according to the seller. Rule of thumb is primary
 must be ten times the accuracy of secondary, that leaves me with an
 uncertainty of +/-60ppmdoes seem a bit muchoh well, if necessary,
 I'm willing to be the only beer-nuts member.
 
 
 
 
 On Tue, Aug 19, 2014 at 4:12 PM, Todd Micallef tmical...@gmail.com wrote:
 
  Stan,
 
  I recently picked up some of these ...
 
  http://www.douglasconnection.com/Furez-TSTWP30NP-Bare-Copper-Banana-Plug-Connectors-Pair-FZTSTWP30NP.htm
 
  They are a little pricey and are made for 12ga wire. I think they are OK
  for semi-permanent use. A lot of use will probably scratch the soft metal.
  I plan on trying them with my Keithley 181 plugged into a low thermal
  scanner.
  The original Keithley cable will be difficult to terminate. I may have to
  go with crimped spade lugs.
 
  Also, I am all for joining a beer nuts group.
 
  Todd
 
 
  On Tue, Aug 19, 2014 at 2:07 AM, Stan Katz stan.katz...@gmail.com wrote:
 
   I'm a self described volt-nut-near-beer. I don't own a 732A/B, or an
   HP3458. I do own HP3456 DMMs that are at the top of my instrumentation
   pecking order.  I have all the necessary gear to calibrate these DMMs
   according to ancient HP documentation. At the top of my cal. chain is the
   731B, called out in HP3456 original documentation.  This hierarchy places
   me in the near-beer, or junior member status of the group. I look forward
   to being educated, and/or corrected on my understanding of the use of
  test
   leads with precision instrumentation.
  
I don't find much ancient HP documentation on test leads. The only
   recommendations in the era of the 3456 back to the 1960's is to use as
   thick a solid lead of pure copper wire as you can find, and insert the
  wire
   into the drill hole on the banana terminal. If the copper is pure, and
  has
   been properly cleaned, the thermal emf's on both identical length leads
   should all be balanced, and cancel out. In any case, pure copper-copper
   connections generate the lowest thermal emf. I  will agree that
  manhandling
   16 gauge solid wire can be very inconvenient.
  
The path I have taken recently is to order Nakamichi gold over copper
   stereo banana plugs for my connections ( I deal in low voltage work
   exclusively), as well as gold plated spade lugs to go under the banana
   screw-downs. ( My budget ruled out gold over beryllium copper Pomona
  brand
   spades. )  I will then experiment between the two connector types. As for
   connections, it seems to me the best course is just to screw down the
   banana plugs, or in the case of the spades, just crimp. I'll wing it on
  the
   crimping, and see if simple tools can perform adequately. I would avoid
   solder, since how can one form identical topological spots of solder on
   every connection, deposited at the exact same place on each connection,
  and
   ensure the exact same weight of solder, to the microgram, on each
   connection. Since my modus operandi is to aim for balanced emfs, I think
   solder is out. Of course, if one wishes to risk one's health, and that of
   the family, one can track down a source of cadmium, and mix up a lot of
  low
   thermal emf solder (cadmium solder is banned in the US, and 

Re: [volt-nuts] Fluke 732A themistor reading

[acbern]

well, re. the resistor, question is how stable it is, not so much absolute 
value. if not very good, your 3458a may be more stable that your reference. vpg 
hermetic foil 4 wire resistors are very stable (1ppm pa) and are cheap (50usd).

re the wire, you should use twisted shielded pair. there are good teflon tsp 
wires with kapton isolation (as used in satellites) on sale on ebay. use copper 
gold plated terminals, around one usd and crimp them. pure copper wire is not 
needed.

cheers

adrian


 Gesendet: Montag, 18. August 2014 um 01:03 Uhr
 Von: Randy Evans randyevans2...@gmail.com
 An: Discussion of precise voltage measurement volt-nuts@febo.com
 Betreff: Re: [volt-nuts] Fluke 732A themistor reading

 I do have an ESI SR1 10Kohm standard, but I'm not sure its accurate
 enough...time to look around I suppose.
 
 BTW, I understand that TV twin lead, the copper wire type, makes a good
 test lead for the 3458 measurements.  It seems reasonable, although the
 leakage resistance might be questionable.
 
 Randy
 
 
 On Sun, Aug 17, 2014 at 1:36 PM, Todd Micallef tmical...@gmail.com wrote:
 
  Randy,
 
  Next thing you know, you will be looking at a 10K standard resistor to go
  with that 3458A and possible 732A.
 
  Todd
 
 
  On Sun, Aug 17, 2014 at 3:51 PM, Randy Evans randyevans2...@gmail.com
  wrote:
 
   Todd and Bill,
  
   Thanks for the input.  The 3.6 K thermistor reading seems viable and i
  will
   pursue it further.
  
   I may have over committed myself to modifying the HP-419A, the Fluke
  845A,
   buying the 3458A and looking at buying a Fluke 732A.
  
   So much to do and so little time.
  
   Thanks again,
  
   Randy
  
  
   On Sun, Aug 17, 2014 at 11:48 AM, Bill Gold wpgold3...@att.net wrote:
  
Randy:
   
I have 6 ea Fluke 732A instruments.  The results of being an over
  the
edge and deeply obsessed Volt Nut, they just kept adding
  (reproducing?)
over the years.  My readings for the themistors range from 3.407K OHMS
  to
4.514K OHMS and all work just fine.  3.6K OHMS would seem just fine to
   me.
It really depends upon the final inside temp of the oven assembly.  The
   one
with 3.407K OHMS measures around 47.5 degrees C while the others are
   around
45 C.  It is the stability of this reading over time that is very
important.
Fluke says that it could change as much as 10 ohms per month but mine
  are
rock solid for years and years.
   
Bill
   
- Original Message -
From: Randy Evans randyevans2...@gmail.com
To: volt-nuts@febo.com
Sent: Sunday, August 17, 2014 11:08 AM
Subject: [volt-nuts] Fluke 732A themistor reading
   
   
 Can anyone tell me what value to expect for a Fluke 732A thermistor
 reading?  I am looking to get a used 732A and one of the things I was
told
 to look for is to measure the thermistor reading after the unit has
heated
 up for at least an hour.  I saw in one of the posts that a typical
 reading was 4950 ohms.  One vendor I asked said he measured about
  3600
ohms
 after a two hour warmup. I was concerned that this is too low.  What
  do
you
 guys think?

 Thanks,

 Randy
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Re: [volt-nuts] HP-419 and Fluke 845 Modifications

[acbern]

I have no personal experience with the 845, however am using the keithley 155 
as nullmeter fo precision calibration. I had used the 182-M (a low noise 
version of the 182) and other digital gear before such as the 2182, and the 155 
performs very well, is easy to use with not much noise and very stable. I have 
seen no reason to buy a 845 or modify the 155, it is very nice as it is.



 Gesendet: Mittwoch, 06. August 2014 um 04:30 Uhr
 Von: R.Phillips phill...@btinternet.com
 An: Discussion of precise voltage measurement volt-nuts@febo.com
 Betreff: Re: [volt-nuts] HP-419 and Fluke 845 Modifications

 Hi Frank
 I have read your comments on the make-up and performance of the 845, so how 
 do you compare the Keithley 155 which I think was a later design ?
 Roy
 
 
 -Original Message- 
 From: Frank Stellmach
 Sent: Tuesday, August 05, 2014 10:33 PM
 To: volt-nuts@febo.com
 Subject: [volt-nuts] HP-419 and Fluke 845 Modifications
 
 Hi Randy,
 to modify the 845 with a modern chopper OpAmp is a great idea, and will
 for sure improve its performance, rather than degrade it.
 
 Fluke never specified the leakage currents of its chopAmps, neither in
 the 845, nor in the 332 / 335 or 334 MOSFET Chopamps..
 
 The real replacement input resistance was never specified, only the
 isolation resistance, but not described, against which potential, or in
 which arrangement. Compare that to FET and Chopper OpAmp specifications!
 
 And the optical chopper of the 845 goes into bipolar transistors, not
 even FETs were used!
 Therefore, the resulting input currents, caused by imperfections of the
 optical chopper, may also be in the high pAs, or nA, nobody ever has
 measured that, but will also give arithmetical 10E13 Ohm at voltage
 differences below µV level...
 
 The great thing about the 845 is its 1kV isolation of input to monitor
 output, but this will not be changed, if you replace the bipolar /
 optical chopper amplifier stuff..
 
 I think, nobody dared to modify the 845, or questioned it, because this
 instrument is a myth, indicated by the price, you still encounter on
 ebay...
 
 
 For the Hp419, everything i described is  the same here, the difference
 of this circuitry is the lack of the isolation transformers only.
 
 Therefore, go ahead, and maybe - please specify the bias currents before
 / after modification.
 
 Frank
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Re: [volt-nuts] Matched resistors

[acbern]

yes, charge injection is an issue with all these switches and these also vary, 
in other words are somewhat unpredictable. now some of this may be compensated 
by a bigger c, but there are natural limits too. so for a production unit to 
sell, this would probably be a killer, but also for home-use, how do you 
predict the behavior over time?

another option to use if you want to stay away from resistors is the 
pwm-solution as implemented by datron in e.g. their 4910. the pwm signal can 
today of course be done by uCs.


 Gesendet: Montag, 21. Juli 2014 um 22:28 Uhr
 Von: Bob Smither smit...@c-c-i.com
 An: Discussion of precise voltage measurement volt-nuts@febo.com
 Betreff: Re: [volt-nuts] Matched resistors

 On 07/17/2014 10:26 AM, Randy Evans wrote:
  Frank,
 
  The high cost is my concern, although high performance demands high price
  typically.  I am trying to double the voltage reference from either an
  LM399 or LTZ1000, hence the need for precision matched resistors for a x2
  non-inverting amplifier (using a LT1151 precision op amp).  An alternative
  I am investigating is using the LTC1043 in a voltage doubling circuit as
  shown in Linear Technology app note AN 42, page 6, Figure 16.  It states
  that Vout = 2xVin +/- 5 ppm.  I am less concerned about the absolute
  accuracy than I am about the long term stability.  I assume that a high
  quality capacitor is required (low leakage, low ESR, low dielectric
  absorbtion, etc.) but the circuit does not appear to be dependent on the
  absolute value of the capacitors.  I'm not sure if the two 1uF caps  need
  to be matched.  If they do then that would be a show stopper.
 
  Does anyone have any experience using the LTC1043 in such a circuit?
 
 Hi Randy,
 
 There are some other error sources that might need to be considered when using
 the LTC1043.
 
 I have not used the LTC1043, but note that on the data sheet there is a small
 charge injection at each of the switch pins. In the multiply by 2 circuit 
 shown
 on the data sheet they are using 1 ufd caps.  Typical charge injection 
 (depends
 on voltage level) is 8 pC. With the 1 ufd caps this is 8 uV.  I assume there 
 is
 some offsetting effect - but this might be a significant contributor to the 5
 ppm error that is mentioned.
 
 There is also a 6 nA (typical) leakage mentioned.  During the hold time (
 about 1 msec) of the output 1 ufd cap this comes to 6 uV.
 
 Regards,
 Bob Smither
 
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Re: [volt-nuts] Matched resistors

[acbern]

and yes, I forgot: only down-dividing of course, so to reach 10V, two LTZ1000 
would be needed in series. advantage is that noise statistically is reduced by 
factor of about 1.4. formally also applies to drift.


 Gesendet: Montag, 21. Juli 2014 um 20:28 Uhr
 Von: Bob Smither smit...@c-c-i.com
 An: Discussion of precise voltage measurement volt-nuts@febo.com
 Betreff: Re: [volt-nuts] Matched resistors

 On 07/17/2014 10:26 AM, Randy Evans wrote:
  Frank,
 
  The high cost is my concern, although high performance demands high price
  typically.  I am trying to double the voltage reference from either an
  LM399 or LTZ1000, hence the need for precision matched resistors for a x2
  non-inverting amplifier (using a LT1151 precision op amp).  An alternative
  I am investigating is using the LTC1043 in a voltage doubling circuit as
  shown in Linear Technology app note AN 42, page 6, Figure 16.  It states
  that Vout = 2xVin +/- 5 ppm.  I am less concerned about the absolute
  accuracy than I am about the long term stability.  I assume that a high
  quality capacitor is required (low leakage, low ESR, low dielectric
  absorbtion, etc.) but the circuit does not appear to be dependent on the
  absolute value of the capacitors.  I'm not sure if the two 1uF caps  need
  to be matched.  If they do then that would be a show stopper.
 
  Does anyone have any experience using the LTC1043 in such a circuit?
 
 Hi Randy,
 
 There are some other error sources that might need to be considered when using
 the LTC1043.
 
 I have not used the LTC1043, but note that on the data sheet there is a small
 charge injection at each of the switch pins. In the multiply by 2 circuit 
 shown
 on the data sheet they are using 1 ufd caps.  Typical charge injection 
 (depends
 on voltage level) is 8 pC. With the 1 ufd caps this is 8 uV.  I assume there 
 is
 some offsetting effect - but this might be a significant contributor to the 5
 ppm error that is mentioned.
 
 There is also a 6 nA (typical) leakage mentioned.  During the hold time (
 about 1 msec) of the output 1 ufd cap this comes to 6 uV.
 
 Regards,
 Bob Smither
 
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Re: [volt-nuts] AC Voltage Measurement Standards

[acbern]

I have a set of 7 TVCs, from 1 to 100V. having them all calibrated externally 
is just too expensive. There is no doubt that having all 7 TVCs calibrated at 
NIST or PTB, wherever you are, is much more precise, I will just not spend it 
and live with the accuracy I get. 
As source I am using a Datron 4808, as nanovolt meter an Agilent 34420. Problem 
with this is, you pointed it out, Agilent does not specify transfer accuracy, I 
am in contact with them, so far no outcome though, not sure there will be any. 
So I have not yet completed my error calculation for the TVC cal. I will 
probably end up doing some calculations based on data sheet an then vaildate by 
measurement. Need that on the 10mv range only, so effort is limited. 
additionally I also have a ratio transformer, which is good to about 10kHz, 
that also allows for validating the TVC results by comparison in lower 
frequency ranges and narrow down the tolerances.
I do have a 182-M, but do not trust it, I saw a lot of drift doing some other 
measurements although it passes performance verification, and I just got a 
2182, which has an issue that needs to be fixed first. I need to say the 34420a 
is very stable with the digital filter switched on and you can see the 
nanovolts walk until the TVC stabilizes. vice versa, if you have an issue in 
the setup (thermal drifts...), you also seethat very well, so the filter is not 
hiding this.
as far as your comment re. calibrating a set of resistor cal from one 
calibrated one, whats wrong with it? if you do that with a stable voltage and 
by voltage divider measurement using the linearity of the 3458A, you end up 
with pretty decent accuracies. I cannot comment on the 242, just did some quick 
checks some time ago and my quick assessment then was it is worse/not better 
than the 3458a method.
 

 Gesendet: Mittwoch, 09. Juli 2014 um 16:35 Uhr
 Von: Todd Micallef tmical...@gmail.com
 An: Discussion of precise voltage measurement volt-nuts@febo.com
 Betreff: Re: [volt-nuts] AC Voltage Measurement Standards

 I would like to know more about your setup. Which source(s) are you using
 for the input and which nanovoltmeter(s) are you using to transfer the 10V
 TVC to your other converters? I remember you asking on PMEL forum about the
 accuracy of using a 34420A nanovoltmeter. I did not see a response as to
 whether you opted for an alternative like Keithley 2182(A) or a low noise
 preamplifier connected to a 3458A.
 
 I have done some reading about how NIST transfers their calibrations using
 two TVC's in parallel and I am guessing that is what you are doing.
 
 http://www.nist.gov/pml/div684/acdc/tcs.cfm
 
 To transfer the accuracy up/down to other TVC's at different rated voltages
 appears to be a difficult task since they typically need at least half the
 rated max voltage to be within spec. It would be similar to starting with a
 SR104 standard and transferring its value through a set of SR1010 and
 SR1050 resistors using an ESI 242.
 
 I have a few AC sources, and I would like to be able to verify my TVC's
 without sending all of them out for cal. Ballantine quoted $600+ per TVC
 and I haven't checked what Fluke would charge for each A55.
 
 Todd
 
 
 I personally did the following: I got a Ballantine 1605A transfer
  voltmeter. This is comparable to the 792A in a way, except it was much
  cheaper. It is automatic, much easier to use than the Fluke 540 and goes up
  to I think 100MHz. This can be used for percision calibrations as a working
  standard. The calibration of this meter as well as others (e.g. the 3458A
  in its AC mode) I am doing with a set of thermal converters (0.5V to 100V).
  One of which (10V) has been externally calibrated up to 30MHz, cal of the
  others are derived from it. That way I am deriving everything from a very
  precisely (few ppm) calibrated 10V TVC. Overall, this saves cost on the
  calibration side, allows for high accuracy and measurement speed is good.
 
 
 
 
 
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Re: [volt-nuts] AC Voltage Measurement Standards

[acbern]

in a nutshell, what i am doing is that I first establish the dc (+/-) output of 
the ref. TVC at nominal and then determine the ac voltage from a precision, 
highly linear (datron 4808) ac source that generates that default output 
voltage at the key frequencies. that establishes a set of ac voltage settings. 
for these the deviations of the TVC are known from the calibration. then I do 
the same with the TVC to be calibrated. (factor of 2 nom. voltage is important 
to stay within allowable range). that way you can link both.
sure, sending all to cal is more precise, if you get the right lab at least, 
but also very expensive.

would sure be interested in your tech paper



 Gesendet: Donnerstag, 10. Juli 2014 um 13:27 Uhr
 Von: Stephen Grady grady.st...@gmail.com
 An: 'Discussion of precise voltage measurement' volt-nuts@febo.com
 Betreff: Re: [volt-nuts] AC Voltage Measurement Standards

 Todd and anyone else would is interested,
 
 Measuring a Thermal Converter against another Thermal Converter is a bit of
 a black art. The main problem is thermal converters are a square law device
 that is if you change the input voltage by a factor of 2 the output voltage
 will change by a factor of approximately 4. Now I say approximately because
 for most thermal converters like the Fluke 540B, A55, Ballantine and Holts
 the actual factor can be anywhere from 1.4 to 1.8 due to losses in the
 thermal converter. In the literature you often see this factor refer to as
 the N factors. Each thermal converter will have its own N factor which must
 be measured to make sense of the measurements.
 
 It even becomes more difficult in that the AC-DC difference of a thermal
 converter is defined as (Vac-Vdc)/Vdc where Vac and Vdc are the inputs to a
 thermal converter which give an equal output from the converter. Also Vdc is
 the mean of the forward and reverse DC voltages. The problem is that when
 you have two converters connected in parallel you cannot balance both
 converters AC and DC inputs to produce equal voltage out of the converters
 at the same time because each converter has its own AC-DC difference and its
 own N factor.
 
 It anyone is interested I can send them a technical paper that describes
 this process and the appropriate math to use but I cannot send it to the
 list due to copyright issues.
 
 Kind Regards,
 
 Stephen Grady
 Sydney Australia
 
 
 -Original Message-
 From: volt-nuts-boun...@febo.com [mailto:volt-nuts-boun...@febo.com] On
 Behalf Of Todd Micallef
 Sent: Thursday, 10 July 2014 2:36 AM
 To: Discussion of precise voltage measurement
 Subject: Re: [volt-nuts] AC Voltage Measurement Standards
 
 I would like to know more about your setup. Which source(s) are you using
 for the input and which nanovoltmeter(s) are you using to transfer the 10V
 TVC to your other converters? I remember you asking on PMEL forum about the
 accuracy of using a 34420A nanovoltmeter. I did not see a response as to
 whether you opted for an alternative like Keithley 2182(A) or a low noise
 preamplifier connected to a 3458A.
 
 I have done some reading about how NIST transfers their calibrations using
 two TVC's in parallel and I am guessing that is what you are doing.
 
 http://www.nist.gov/pml/div684/acdc/tcs.cfm
 
 To transfer the accuracy up/down to other TVC's at different rated voltages
 appears to be a difficult task since they typically need at least half the
 rated max voltage to be within spec. It would be similar to starting with a
 SR104 standard and transferring its value through a set of SR1010 and
 SR1050 resistors using an ESI 242.
 
 I have a few AC sources, and I would like to be able to verify my TVC's
 without sending all of them out for cal. Ballantine quoted $600+ per TVC and
 I haven't checked what Fluke would charge for each A55.
 
 Todd
 
 
 I personally did the following: I got a Ballantine 1605A transfer
  voltmeter. This is comparable to the 792A in a way, except it was much 
  cheaper. It is automatic, much easier to use than the Fluke 540 and 
  goes up to I think 100MHz. This can be used for percision calibrations 
  as a working standard. The calibration of this meter as well as others 
  (e.g. the 3458A in its AC mode) I am doing with a set of thermal
 converters (0.5V to 100V).
  One of which (10V) has been externally calibrated up to 30MHz, cal of 
  the others are derived from it. That way I am deriving everything from 
  a very precisely (few ppm) calibrated 10V TVC. Overall, this saves 
  cost on the calibration side, allows for high accuracy and measurement
 speed is good.
 
 
 
 
 
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Re: [volt-nuts] Buying HP-3458A

[acbern]

well, some time ago, when I bought my first 3458A, I looked into the data sheet 
of the 3458a and I figured that the basic accuracy of their standards is not 
terribly good. 2ppm each, you need to add this to all their specs. dont get me 
wrong, for most it is really sufficient, but as we are all a little nuts, I 
felt I would rather spend the money needed to calibrate the 3458a on a yearly 
basis for something else.
so I use a 732a and a 4910 as voltage references, and a very stable resistor. 
the 732a can be calibrated to appr. 1ppm at relatively little cost here, the 
10k resistor is in the 2ppm range, but simply because I did not want to spend 
the money for sub 1 ppm. calibrating both on a yearly basis is much cheaper 
than sending the 3458a for cal. I still need to establish the stability of the 
references, but the voltage references should be below 1ppm drift pa, the 10k 
below 0.5ppm (fluke also has a good appnote on establishing sub ppm stability 
with te 732A). so eventually I can move to a cal once every 2 years or so. and 
of course now, I can do the cal every 90 days to maintain 90 day accuracy. do 
that through an eternal lab, costs you a fortune.

now with these, you have only adjusted the meter, you still need to do 
performance verification. to do this, you need to have more precision gear, 
which i already had to some extent. the good thing is, some of it does not need 
cal., or is self-cailbrating.
all dcv is valiated with a 752a divider (self-calibrating) and a 
nanovolt-nullmeter. current validation is with a set of precision resistors, 
these are derived from the calibrated 10k with proper error propagation calc. 
it turns out that using the voltage divider method with the high linearity of 
the 3458a meter (in conjunction with a very stable voltage source) achieves 
precise enough resistor accuracies to do current verification. for ac you need 
a set of thermal converters or an ac transfer standard (ballantine 1605 e.g.) 
and a ratio transformer. question of course is, do you really need the ac 
function verified, most applications really focus on the dcv and ohms 
measurement. so here some money can be saved on gear.
again, this allows to keep the 3458a at a much higher acc. level than using an 
external cal lab, especially if you do it on a 90 day basis. or you could opt 
to just verify selected functions, even on a more regular basis. all depends on 
your needs.
performance verification is time consuming though, if you do it well. 



 Gesendet: Sonntag, 06. Juli 2014 um 19:18 Uhr
 Von: Attila Kinali att...@kinali.ch
 An: Discussion of precise voltage measurement volt-nuts@febo.com
 Betreff: Re: [volt-nuts] Buying HP-3458A

 Moin moin,
 
 On Sun, 6 Jul 2014 10:45:51 +0200
 acb...@gmx.de wrote:
 
   so for me, since I am also calibrating the unit myself,
 
 I would be very much interested in how you calibrate the 3458 and
 what you use as calibration standard.
 
   Attila Kinali
 
 -- 
 I pity people who can't find laughter or at least some bit of amusement in
 the little doings of the day. I believe I could find something ridiculous
 even in the saddest moment, if necessary. It has nothing to do with being
 superficial. It's a matter of joy in life.
   -- Sophie Scholl
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[volt-nuts] transfer accuracy

[acbern]

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