[volt-nuts] Fluke 732A Questions

J. L. Trantham jltran at att.net
Mon Dec 30 21:28:32 EST 2013


Sounds like you are further along in the 'volt-nut' process than I am.  I'll
have to chase down the NIST paper.  I have been very impressed by the
stability of the 732A and the 735C.

Unfortunately, I don't have any documentation on the 735C and only the early
manual for the 732A.

I would be interested in the specifics of the battery check procedure in
your manual.  Unfortunately, my manual does not have a page 2-9.

I note that there are two banana jacks on the front of the battery module,
both black, one connected to ground and the other not connected to anything.
Any idea of what they are for?

I always like to keep equipment as 'original' as possible.  If I can't find
the correct connector, I'll find something similar that will fit in the same
hole and use it instead.  We'll see what I hear from Fluke and Hypertronics.

Also, how do you get your 732A calibrated?  Do the batteries last long
enough to ship overnight to a facility?

Thanks for the info.


-----Original Message-----
From: volt-nuts-bounces at febo.com [mailto:volt-nuts-bounces at febo.com] On
Behalf Of Bill Gold
Sent: Monday, December 30, 2013 7:03 PM
To: Discussion of precise voltage measurement
Subject: Re: [volt-nuts] Fluke 732A Questions


    My 732A units vary in thermistor resistance from 3.408K ohms to 4.514K
ohms and have been extremely stable to with in +/- 5 ohms for years now.  I
did measure the oven temperature of the one with the 3.408K ohms just to see
what was causing the thermistor resistance to be a little low and came up
with about 47 degrees centigrade, as best as my equipment would allow me to
measure it.  Equipment was a Fluke 80TK thermocouple module, a Fluke 80 PK-1
thermocouple bead and a HP 3456A DVM.  I put shrink wrap around the bead and
then threaded the bead into the temperature oven through one of the
adjustment holes in the front panel and made sure that it was far into the
oven, probably around the middle.  Then I checked another unit that read
4.5K ohms and it read around 43 degrees C so all of that made sense.  I
believe I saw somewhere that the spec was 45 degrees C +/- 2 C.

    I did have to change the jumpers on the "Calibration PCB Assembly" on
one of my units so that it would match other 732A units that were "In Cal"
and had certified values.  But that unit has since drifted down at a rate of
around 1.2 ppm per year which is with in specs but a little more than I have
seen from other units.  Recently this unit has suddenly quit drifting down
and seems a lot more stable now.  That was S/N 459xxxx.  I have a S/N
343xxxx which has been proven rock solid for years now at around +/- .3 ppm
and just seems to have "DC noise" stability as it just goes up a little and
then down a little and never needed any adjustment.  I also have a S/N
460xxxx which is extremely stable also.  So I guess that age does seem to
factor into stability as well as how long they have been powered up.  But
the only way to insure that you have a good "volt" is to have at least 4
units and then inter-compare them periodically following NIST (NBS)
Technical Note #430.  While 430 was written for Saturated Standard Cells,
the technique seems to work just fine at 10 volts also.  You can also find
this measurement technique in the 1st Fluke "Calibration - Philosophy in
Practice" book published around 1974.

    I gave up on the "unobtainium" connector on the back of the battery pack
very quickly.  I drilled a 1/4 " holes on either side of the "unobtainium"
connector, after removing it, and used two single miniature banana jacks to
allow me to connect to the batteries for the purpose of checking their
performance as described in the 732A manual page 2-9 in manual P/N 788414
May 1986.  I should probably turn in my resignation as a "volt nut" for this
action but it works.  KISS.


----- Original Message -----
From: "J. L. Trantham" <jltran at att.net>
To: <volt-nuts at febo.com>
Sent: Saturday, December 28, 2013 2:51 PM
Subject: [volt-nuts] Fluke 732A Questions

> I have reviewed the prior postings on Volt-nuts (a very rewarding review,
> BTW)) regarding the 732A and have two questions:
> 1.        Has anyone determined the part number, or a source, for the
> plug to J10, the external power connector for the 732A-7005 battery pack?
> noted some postings recently about this but did not find a definitive
> response regarding the identity of this plug.  The alternative would
> to be a complete replacement of J10 and its plug, as long is it all fits
> the opening in the panel.  I hate to 'bore holes' in vintage equipment.
> 2.       The oven thermistor in my 'new to me' unit measures 4229 ohms
> an ohm or two) after the unit has warmed up for a week or so.  I note the
> manual refers to 3K to 4K for the value of this thermistor when the unit
> 'stable' as well as other's posting values in the mid 3500's ohms for
> units.  Should I be concerned?  The unit seems to be stable to within
> 2 uV over about a week (as measured by my 3458A - see below).  Should I
> the unit and try to measure the oven temperature or just be satisfied that
> the unit seems to be working?
> I had to replace the four 6V 4AH SLA batteries and they charged up
> appropriately as judged by the front panel LED's.  I had to remove the
> 'jumper' for the '40' option on the A7 board and connect the jumper to the
> '20' and '10' options (total of '30') in order to get the unit to adjust
> 10.0000000 VDC on my 'Agilent In Cal'd' 3458A.
> The need to change the jumpers, perhaps, could be just an ageing issue or,
> on the other hand, a 'temperature' issue with the oven.
> Should I open the unit and directly measure the temperature (supposedly
> about 48 degrees C) or just be satisfied with what I have?
> My recently added 735C also needed moving some 'jumpers' in order to get
> 'on scale', as determined by my 3458A, although it's thermistor measures
> about 3330 ohms (after being on for several weeks).
> Thanks for everyone's help.
> Joe
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