Re: [volt-nuts] Datron 4600 Transconductance Amplifier

[Todd Micallef]

Dave,

I have the same problem. I ordered some connectors from an auction and they
are due to arrive this week. They were ordered as a set since the female
connector was hard to find.

I was going to ask the group if both cables were straight through and if
any of the wires were of any special type like STP.

Todd

On Monday, July 10, 2017, David C. Partridge 
wrote:

> I'm looking for the cables to connect this to a 4808 and for the Service
> Manual.
>
> It's also known as Option 60 if that helps any.
>
> Dave
>
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Re: [volt-nuts] Problems with 720A

[David C. Partridge]

Further study of the schematics leads me to think that one should check the oil 
bath resistors by setting decade A to CAL and the main function switch to CK B 
(to isolate R313 and R314).

If I do this most of them read as expected around 9.89k but R302 reads 9.711k 
and R311 reads 9.793k.

Dave

-Original Message-
From: volt-nuts [mailto:volt-nuts-boun...@febo.com] On Behalf Of David C. 
Partridge
Sent: 10 July 2017 14:28
To: 'Discussion of precise voltage measurement'
Subject: Re: [volt-nuts] Problems with 720A

I just realised that with the dials set for zero that R311 will be shunted by 
the following decades.  I think that with the A dial set for 0.8 that a 
measurement of R311 should be valid.

If that's right, then I get 9K79 which still seems low.

Dave

-Original Message-
From: volt-nuts [mailto:volt-nuts-boun...@febo.com] On Behalf Of David C. 
Partridge
Sent: 10 July 2017 13:13
To: 'Discussion of precise voltage measurement'
Subject: Re: [volt-nuts] Problems with 720A

If I have read that right I'm getting what I think are "odd" readings across 
R302 (9K710) (pins 21-22)  and R311 (7K395) (pins 3-4) when the dials are set 
to all zero.  I think both should read about 9K9.

Could someone who has a 720A check the resistance across pins 21-22 and 3-4 on 
the oil bath and let me know the numbers?

Thanks
Dave

-Original Message-
From: volt-nuts [mailto:volt-nuts-boun...@febo.com] On Behalf Of David C. 
Partridge
Sent: 10 July 2017 12:20
To: 'Discussion of precise voltage measurement'
Subject: [volt-nuts] Problems with 720A

You knew this was coming I'm sure:  It was almost inevitable that there would 
be problems with the 720A!

While trying to self-calibrate the 720A, (CAL A) the at the 0.1 and 0.10 
settings the null meter was way out with around 100mV out of balance, and the 
A.1 and A.10 pots seemed not to do anything.

I'm trying to work out from the schematic what's likely to be wrong, but so far 
am not clear where the fault lies.

I *think* that when I have the main switch set to CAL A and the A decade set to 
0.1 that I'm balancing R311, R1044, R1042 and R1041  against the leg of the 
bridge comprising R1, R206, R207, R208 and R209

Similarly for the 1.0 setting of the A decade, I think the resistors are R302, 
R1008, R1006, and R1005.

Have I read this correctly?

Thanks
Dave

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Re: [volt-nuts] Problems with 720A

[David C. Partridge]

I just realised that with the dials set for zero that R311 will be shunted by 
the following decades.  I think that with the A dial set for 0.8 that a 
measurement of R311 should be valid.

If that's right, then I get 9K79 which still seems low.

Dave

-Original Message-
From: volt-nuts [mailto:volt-nuts-boun...@febo.com] On Behalf Of David C. 
Partridge
Sent: 10 July 2017 13:13
To: 'Discussion of precise voltage measurement'
Subject: Re: [volt-nuts] Problems with 720A

If I have read that right I'm getting what I think are "odd" readings across 
R302 (9K710) (pins 21-22)  and R311 (7K395) (pins 3-4) when the dials are set 
to all zero.  I think both should read about 9K9.

Could someone who has a 720A check the resistance across pins 21-22 and 3-4 on 
the oil bath and let me know the numbers?

Thanks
Dave

-Original Message-
From: volt-nuts [mailto:volt-nuts-boun...@febo.com] On Behalf Of David C. 
Partridge
Sent: 10 July 2017 12:20
To: 'Discussion of precise voltage measurement'
Subject: [volt-nuts] Problems with 720A

You knew this was coming I'm sure:  It was almost inevitable that there would 
be problems with the 720A!

While trying to self-calibrate the 720A, (CAL A) the at the 0.1 and 0.10 
settings the null meter was way out with around 100mV out of balance, and the 
A.1 and A.10 pots seemed not to do anything.

I'm trying to work out from the schematic what's likely to be wrong, but so far 
am not clear where the fault lies.

I *think* that when I have the main switch set to CAL A and the A decade set to 
0.1 that I'm balancing R311, R1044, R1042 and R1041  against the leg of the 
bridge comprising R1, R206, R207, R208 and R209

Similarly for the 1.0 setting of the A decade, I think the resistors are R302, 
R1008, R1006, and R1005.

Have I read this correctly?

Thanks
Dave

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Re: [volt-nuts] Guidance requested.

[Charles Steinmetz]

David wrote:


So please how best to proceed from here?


The Fluke 732A is by far the most accurate and most stable voltage 
reference you have.  There are only a few cal labs worldwide that can 
calibrate it to an uncertainty that does it justice (1/10 ppm).  Most 
good to excellent cal labs have 10v DC uncertainties from 1-10 ppm.


SO:  First, have the 732A calibrated by one of those few labs.  I 
strongly favor the Fluke US cal facility (Fluke Park Laboratory, 
Everett, WA, USA, NVLAP Lab Code 105016-0), with an accredited DC 
calibration uncertainty of 100nV at 10v.  However, it may be an issue 
getting it back to you still under power from there (IIRC, you are in 
the UK).  I maintain three 732As and calibrate each one annually on a 
rotating schedule, one every 4 months.  I built a shipping container 
with internal batteries that will keep the 732A powered for three days, 
if necessary, and an internal charger so all Fluke has to do is plug the 
shipping container in to recharge them.


If the choice comes down to a lab that can calibrate the 732A with full 
accuracy (1/10 ppm), but it will arrive back to you "cold," and a lab 
that cannot calibrate it to that standard in the first place, I'd choose 
the former.  In my experience, 732As generally retrace within 0.25 ppm 
if re-powered within a few days.  IOW, I recommend the Fluke US cal lab 
unless you have a trustworthy cal lab with 1/10 ppm uncertainty local to 
you.  (But although experience suggests that you can rely on the 
re-powered standard to be within 0.25 ppm of the calibrated value, you 
will have lost NIST traceability.)


So whatever you do, have the 732A calibrated *properly* before you do 
anything else.


Also, put the 732A on its own dedicated 2-3 kW "online"-type UPS.  If 
the UPS runs nothing but the 732A, it should carry you through all but 
the longest power outages.  Adding external batteries is a good plan 
(industrial "online" UPSs support this).  I have a backup generator, but 
even so my UPS system will run the 732As, my primary frequency 
references, and transfer DMM for more than a week if necessary.


Note that "calibrating" the 10v output of a 732A generally does not 
involve adjusting it.  Rather, the cal lab will tell you its actual 
voltage to 1/10 ppm, and you will calculate from that value when you use 
it.  I usually have a new-to-me standard adjusted the first time I have 
it calibrated, unless I obtained it with its full calibration history 
from an unimpeachable source.  I obtained two of my 732As this way, one 
I repaired.  I had that one adjusted at its first two calibrations.


Finally, note that proper calibration of a 732A is not cheap.  Mine are 
on a calibration contract, and I still pay over $1000 (plus overnight 
shipping two ways on 40+ pounds).  That said, the real value of a 732A 
is its calibration history.  Without a proper calibration and the 
calibration history, it is just another voltage reference that needs 
characterization before it can be relied on.


Best regards,

Charles


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[volt-nuts] Problems with 720A

[David C. Partridge]

You knew this was coming I'm sure:  It was almost inevitable that there
would be problems with the 720A!

While trying to self-calibrate the 720A, (CAL A) the at the 0.1 and 0.10
settings the null meter was way out with around 100mV out of balance, and
the A.1 and A.10 pots seemed not to do anything.

I'm trying to work out from the schematic what's likely to be wrong, but so
far am not clear where the fault lies.

I *think* that when I have the main switch set to CAL A and the A decade set
to 0.1 that I'm balancing R311, R1044, R1042 and R1041  against the leg of
the bridge comprising R1, R206, R207, R208 and R209

Similarly for the 1.0 setting of the A decade, I think the resistors are
R302, R1008, R1006, and R1005.

Have I read this correctly?

Thanks
Dave

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Re: [volt-nuts] 3458A question

[Domenico Crupi]

I noticed this behaviour after autocal also in my unit.
I think it may be caused by autocal procedure that exercise some relay
switch and this is resulting some uV offset due to EMF.
After waiting some time temperature will equalise again and accuracy will
be slight better.
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Re: [volt-nuts] Guidance requested

[David C. Partridge]

Frank and others,

>1kV depends on the 100:1 divider of your special 3458A instrument, it can be 
>precise as a few ppm only, but unprecise as 12ppm,
>as described in the specification. 

The 3458A readings for all ranges except 1000V are now within the spec of the 
Datron 4808 (between 2.8ppm and 5.6ppm depending on range)

On the 1000V range for voltages up to and including 700V the 3458A reading are 
consistently low low but within the Datron spec of +/-5.6ppm
For voltages of 800V and above the 3458A reading starts off just within or 
close to spec of the Datron of 5.6ppm, but then falls away as the divider warms 
up (I think).

Here are the settling levels:

800V is 799.9946V 7.3 to 7.4ppm low
900V is 899.9901V 9.9ppm low
1000V is 999.9886V 11.2ppm low

Whether it is the Datron or the 3458A I'm not yet sure. That's why I'm doing 
the 720A alignment so I can cross check.

Dave

-Original Message-
From: volt-nuts [mailto:volt-nuts-boun...@febo.com] On Behalf Of Frank Stellmach
Sent: 10 July 2017 07:25
To: volt-nuts@febo.com
Subject: [volt-nuts] Guidance requested

So I have:

1) A Datron 4808 (not calibrated recently AFAIK, and no way to check),
2) A 3458A which is about 6 months out of calibration (sadly not by Keysight),
3) Three 7081s two of which are also 6 months out of calibration against the 
3458A,
4) A 720A.
The readings of the output of the Datron for the 1V, and 10V, 100V and 100V 
ranges on the 3458A (NPLC100) are:
1.0177V (high limit 1.0480V),
9.964V (low limit 9.720V, 99.999380V and climbing slowly (low limit 
99.999550V) In spec some five or so minutes later.
999.98xxxV (and falling) (low limit 99.99450V) So definitely out of spec To be 
fair both the 4808 and 3458A have only been on for about 8 hours - things may 
improve :).

So please how best to proceed from here?
Thanks Dave



Dave,
at first, all instruments need a stable temperature environment, otherwise ppm 
measurements are meaningless, I recommend setting up the lab in the basement, 
if available.

The 3458A is stable after about 2h, or 4h at most.
Check its inernal temperature, and use ACAL DCV frequently.

As the 3458A and the 4808 agree to <1ppm on the 10V range, there's good reason 
that the basic DCV calibration of the 3458A is still fine. Both these 
instruments do not drift that much if they are old vintage, and if they are not 
powered on 24/7/365.
If the 3458A was unpowered most of the time, its reference very probabaly did 
not drift at all.

If your 732A agrees also on 10V within a few ppm, you would have another fix 
point.
Maybe you can send in the 732A for comparison to another volt-nut, or build a 
transportable 7,15xxxV reference with an LTZ1000, as described in the eevblog 
thread.

Because the 3458A is an AUTOCAL instrument, the 1V, 100V readings are precise 
to about the same level, as the 10V range.
The 3458A makes better ratio transfers than the 720A, butter latter is good for 
linearity check, anyhow.
1kV depends on the 100:1 divider of your special 3458A instrument, it can be 
precise as a few ppm only, but unprecise as 12ppm, as described in the 
specification. For 1kV measurements, all instruments need at least 1min 
stabilization before making measurements, due to power induced temperature 
drift.

To use the 720A on 1kV, may not give better accuracy, either, again due to the 
high power drift.
A 752A would be required, or another ACAL instrument, like the 5440A, or the 
5720A.

The references inside the 7081A may drift the most, so I would trust them less.

For Ohm, you may want to follow TiNs proposals.

Frank


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Re: [volt-nuts] Guidance requested

[John Phillips]

I believe that 3458A will be more stable if it is never turned off.
The references are cooked in. There was a problem when production was moved
offshore, the references were stored cold after they had been cooked into
spec. When these units were shipped they did not meat spec. There was a
memo stating that if left on for 6 months the references should return to
spec.
We stored all our 3458As powered up even if we did not anticipate using
them for months.


On Sun, Jul 9, 2017 at 11:24 PM, Frank Stellmach  wrote:

> So I have:
>
> 1) A Datron 4808 (not calibrated recently AFAIK, and no way to check),
> 2) A 3458A which is about 6 months out of calibration (sadly not by
> Keysight),
> 3) Three 7081s two of which are also 6 months out of calibration against
> the 3458A,
> 4) A 720A.
> The readings of the output of the Datron for the 1V, and 10V, 100V and
> 100V ranges on the 3458A (NPLC100) are:
> 1.0177V (high limit 1.0480V),
> 9.964V (low limit 9.720V, 99.999380V and climbing slowly (low
> limit 99.999550V)
> In spec some five or so minutes later.
> 999.98xxxV (and falling) (low limit 99.99450V) So definitely out of spec
> To be fair both the 4808 and 3458A have only been on for about 8 hours -
> things may improve :).
>
> So please how best to proceed from here?
> Thanks Dave
>
>
>
> Dave,
> at first, all instruments need a stable temperature environment, otherwise
> ppm measurements are meaningless,
> I recommend setting up the lab in the basement, if available.
>
> The 3458A is stable after about 2h, or 4h at most.
> Check its inernal temperature, and use ACAL DCV frequently.
>
> As the 3458A and the 4808 agree to <1ppm on the 10V range, there's good
> reason that the basic DCV calibration of the 3458A is still fine. Both
> these instruments do not drift that much if they are old vintage, and if
> they are not powered on 24/7/365.
> If the 3458A was unpowered most of the time, its reference very probabaly
> did not drift at all.
>
> If your 732A agrees also on 10V within a few ppm, you would have another
> fix point.
> Maybe you can send in the 732A for comparison to another volt-nut, or
> build a transportable 7,15xxxV reference with an LTZ1000, as described in
> the eevblog thread.
>
> Because the 3458A is an AUTOCAL instrument, the 1V, 100V readings are
> precise to about the same level, as the 10V range.
> The 3458A makes better ratio transfers than the 720A, butter latter is
> good for linearity check, anyhow.
> 1kV depends on the 100:1 divider of your special 3458A instrument, it can
> be precise as a few ppm only, but unprecise as 12ppm, as described in the
> specification. For 1kV measurements, all instruments need at least 1min
> stabilization before making measurements, due to power induced temperature
> drift.
>
> To use the 720A on 1kV, may not give better accuracy, either, again due to
> the high power drift.
> A 752A would be required, or another ACAL instrument, like the 5440A, or
> the 5720A.
>
> The references inside the 7081A may drift the most, so I would trust them
> less.
>
> For Ohm, you may want to follow TiNs proposals.
>
> Frank
>
>
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> ailman/listinfo/volt-nuts
> and follow the instructions there.
>



-- 

*John Phillips*
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[volt-nuts] Guidance requested

[Frank Stellmach]

So I have:

1) A Datron 4808 (not calibrated recently AFAIK, and no way to check),
2) A 3458A which is about 6 months out of calibration (sadly not by 
Keysight),
3) Three 7081s two of which are also 6 months out of calibration against 
the 3458A,

4) A 720A.
The readings of the output of the Datron for the 1V, and 10V, 100V and 
100V ranges on the 3458A (NPLC100) are:

1.0177V (high limit 1.0480V),
9.964V (low limit 9.720V, 99.999380V and climbing slowly (low 
limit 99.999550V)

In spec some five or so minutes later.
999.98xxxV (and falling) (low limit 99.99450V) So definitely out of spec
To be fair both the 4808 and 3458A have only been on for about 8 hours - 
things may improve :).


So please how best to proceed from here?
Thanks Dave



Dave,
at first, all instruments need a stable temperature environment, 
otherwise ppm measurements are meaningless,

I recommend setting up the lab in the basement, if available.

The 3458A is stable after about 2h, or 4h at most.
Check its inernal temperature, and use ACAL DCV frequently.

As the 3458A and the 4808 agree to <1ppm on the 10V range, there's good 
reason that the basic DCV calibration of the 3458A is still fine. Both 
these instruments do not drift that much if they are old vintage, and if 
they are not powered on 24/7/365.
If the 3458A was unpowered most of the time, its reference very 
probabaly did not drift at all.


If your 732A agrees also on 10V within a few ppm, you would have another 
fix point.
Maybe you can send in the 732A for comparison to another volt-nut, or 
build a transportable 7,15xxxV reference with an LTZ1000, as described 
in the eevblog thread.


Because the 3458A is an AUTOCAL instrument, the 1V, 100V readings are 
precise to about the same level, as the 10V range.
The 3458A makes better ratio transfers than the 720A, butter latter is 
good for linearity check, anyhow.
1kV depends on the 100:1 divider of your special 3458A instrument, it 
can be precise as a few ppm only, but unprecise as 12ppm, as described 
in the specification. For 1kV measurements, all instruments need at 
least 1min stabilization before making measurements, due to power 
induced temperature drift.


To use the 720A on 1kV, may not give better accuracy, either, again due 
to the high power drift.
A 752A would be required, or another ACAL instrument, like the 5440A, or 
the 5720A.


The references inside the 7081A may drift the most, so I would trust 
them less.


For Ohm, you may want to follow TiNs proposals.

Frank


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