Joe, Bill and Charlie
Thank you all for your advice, and for the short term I will leave the 732A
as is. Like you Joe, my 732A arrived with a set of 'dead' SLA batteries -
these were replaced, and its been powered 24/7 since last October, again it
came with no history. I bought mine from a dealer on the West Coast who had
a batch of 14, so I guess that they came from a lab. Its stability is
impressive, and the Thermistor reading is currently 4.5194 K ohms, with only
small variations over time.
My 3458A had a new processor/RAM/ROM board fitted by Agilent - so it has the
latest 'plug-in/power-up' devices which I understand are a great
improvement, and was calibrated just about six weeks ago. I take your point
that the 3458A should be power continuously, but of course the display is of
the fluorescent type which deteriorate over time. This is now less
important, as I have had a new display installed, and the improvement is
great. I certainly agree that the 3458A is very sensitive to temperature
changes and as you advise, I frequently run 'Auto Cal' . I consider the
cost of its refurbishment/calibration to be well worth while, considering
the cost of a new instrument.
Best regards.
Roy
-Original Message-
From: J. L. Trantham
Sent: Saturday, June 14, 2014 1:48 AM
To: 'Discussion of precise voltage measurement'
Subject: Re: [volt-nuts] A Fluke 732A: Return it or keep it?
Roy,
The tool needed to adjust the 732A is both a tool with a recessed metal
blade and a tool with an exposed metal blade. The 10 V adjustment is
certainly the one with the recessed metal blade. The other two use one of
each. I just can't remember which is which. However, if you look at the
service manual (downloadable from Fluke or other sites) you can tell which
is which. All are a 'good ways' in the unit. If you get 'eye to eye' with
the adjustment holes, with a flash light, you can tell what the position of
the 'blade' should be to make the adjustments. Once properly 'in place',
leave the adjustment tool in position and wait a day or so to make sure all
remains stable. Don't forget to 'AutoCal All' the 3458A at least every 24
hours (leaving the 732A and the 3458A on 24/7) while doing this.
My experience with these standards is from a 732A and a 735C. They share a
lot in common. The 735C is 10.0 V only.
Both my units arrived with dead battery packs (NiCd for the 735C and SLA for
the 732A) and no history of performance. When I 'resurrected' them they
were both way off scale. Since I had no history of their prior performance,
I decided I would allow them to 'settle' then adjust them to be 10.000
VDC as best I could do with my Agilent Calibrated 3458A. Both required
making adjustments to their internal 'connections' in order for them to be
'on scale' with the external adjustments. Once adjustments were made, I
have covered the access holes for the adjustments and the 'reset' hole with
tape to minimize ambient air currents.
Both are now very stable. With the 735C, for instance, when I 'AutoCal' the
3458A and read the voltage, it is +/- 1 uV from 10.00 VDC repeatedly.
Tonight, for instance, it reads 10.001 then settles on 9.998. Both
the 735C and the 3458A are on 24/7/365.
I take that as evidence that they have 'stabilized'. My plan is to send my
Opt 002 3458A to Agilent for their 90 day specification Cal then use it to
do a 'final adjustment' to both the 732A and 735C. Once I'm confident that
both have 'stabilized' (which I hope will happen within the 90 day Cal
period), then I hope to send both to Fluke for their 'calibration'.
Once done, my plan is to never adjust them again but, rather, keep track of
their readings with a 3458A.
I agree with others that it is best to track the values rather than to try
to 'adjust' the references. However, if you have no 'history', you get to
start from scratch, or at least that's my opinion.
The 3458A should be about 4 PPM. Hopefully, the Opt 002 with a '90 day
Cal', it will be more like 2 PPM or better. We'll see what Fluke does with
the 735C and 732A, once they have a chance to take a look. Once
'calibrated', I agree it is more important to make sure they are 'in range'
and stable rather than trying to 'adjust' them each time they might go in
for 'cal'.
Hope this helps.
Good luck.
Joe
-Original Message-
From: volt-nuts-boun...@febo.com [mailto:volt-nuts-boun...@febo.com] On
Behalf Of Charles Black
Sent: Thursday, June 12, 2014 11:18 AM
To: Discussion of precise voltage measurement
Subject: Re: [volt-nuts] A Fluke 732A: Return it or keep it?
Hi Roy,
I would like to second Todd's advice about leaving the Fluke 732A's output
voltage adjustment alone. You already have stable outputs and 24 microvolts
high is very acceptable. My Datron 4910 (four output supply) has predictable
digital output level settings that doesn't have any luck involved so it is a
better candidate for resetting the standards than the Fluke 732A. I
