[volt-nuts] Fluke 732A Questions

[Bill Gold]

Joe:

    A correction on the dropout voltage when the "In Cal" light goes out, I
found my notes and it is 21 volts instead of 22 volts.  The way I did this
was to remove the battery pack, AC voltage and then just feed in a power
supply where the battery pack would have delivered it's voltage to the
back-plane mother board.  Then I just reduced the voltage until the light
turned off.  So that means that Fluke was following the battery
manufacturers specs of 5.25 volts at the end of the discharge curve.

    The banana jacks on the battery pack have two jobs.  One is to provide a
very good chassis ground to the battery pack and the other is probably to
guide the pack accurately into the mother board.  One other thing I have
found out the hard way is that the holes in the top plate of the battery
pack where the battery terminals come through are very close to the battery
terminals and can short out to the chassis.  I have made the holes a LOT
bigger to avoid this problem.  This really depends upon the brand of
batteries you are using but after having to repair the regulator board I
would rather be safe than sorry.

    I have 6 Pomona 1756-48 low thermal leads for when I need to be careful
with thermals.  I also have made my own "low thermal"    (I think) using
Pomona 4892 gold plated double banana plugs and Belden 9272 twisted pair
twinax, using a Pomona 1825 for the ground lead.  If I need single banana
plugs to connect to the 732A I use Pomona 4897 gold plated.  I know that
this isn't the best possible low thermal because the wire is tin plated but
I have looked and I can't find a good source of bare copper twisted pair
shielded wire.  When I am making measurements with the home made cables I
just wait a few minutes for the thermals to settle down.  Why Belden 9272?
It was the best choice from what was available at work.  From what I have
seen Pomona was acquired by Fluke and makes special low thermal cables for
Fluke that are not available through the Pomona catalog.

    When you find out from Fluke what services they offer and prices please
let all of us know.

Bill

----- Original Message ----- 
From: "J. L. Trantham" <jltran at att.net>
To: "'Discussion of precise voltage measurement'" <volt-nuts at febo.com>
Sent: Tuesday, December 31, 2013 5:13 PM
Subject: Re: [volt-nuts] Fluke 732A Questions


> Bill,
>
> I have yet to put my 732A though it's paces but I could connect an
external
> power supply, disconnect the AC supply and the battery module and slowly
> decrease the supplied voltage and see what happens when.
>
> I'll try your measurement algorithm for the battery to see when the 'IN
CAL'
> LED goes out and what the current draws are.  If the measured voltage at
J10
> is 27 V, then the actual battery voltage should be about 27.6 V,
accounting
> for the diode in the circuit (unless the current draw during measurement
is
> so low that no voltage drop occurs across the diode).
>
> I found the NIST/NBS Tech Note easily.
>
> I think if I decide to send it out for calibration, I'll use Fluke, if
they
> still calibrate the unit.  I'll call them later this week of next week to
> see what services/accessories they might still have available.
>
> Yes, I wound up with the 735C.  It was easy to replace the NiCd battery
pack
> and bring it 'on scale' by adjusting the 'jumpers' and the front panel
> adjustment.  I now only have to deal with the periodic 'NO CAL' LED
> indication.  I need to study the 732A manual then take a close look at the
> 735C to see how it works on it.
>
> This also brings up the question of 'low EMF cables' for accurate
> measurement.  I have a Fluke 720A K/V Divider on the shelf that I have yet
> to bring out to check to see if it is operational.  Another one of those
> 'projects' for a later time.
>
> Where would one look for 'low EMF cables' to be used in precise
measurement
> experiments and what errors might one expect to find using Pomona gold
> plated Banana Plug cables (which is as good as I have at this time)?
>
> Thanks for the info.
>
> Happy New Year to all.
>
> Joe
>