[volt-nuts] 732A and Prologix received

[Bill Gold]

Randy:

    I get 6 volt 4 amp/hr (or 4.5 amp/hr) batteries and they will fit
perfect.  Power Sonic PS-640, Genesis NP4-6, Panasonic LC-R064R5C and others
that are in this size and package.  Order from one of the usual electronics
distributors like Allied, Mouser, Digikey.  This is a very common battery as
it is used in a lot of "EXIT" signs so they are lighted when the power goes
out.  I don't see how the 12V 7AH will fit as they are too large.  I guess
you could use a 12V 5AH (PS1250) as it is the same size as 2 x 6 volt 4 AH
but the terminals are in the wrong place so you will have to "nibble" out
the aluminum plate that holds them in the 732A battery pack.  You have to be
careful if you use the 12v 5AH as you will have 4 extra battery connection
leads to deal with and connect correctly.  I would stick with the 6V 4AH.
New batteries will last around 12 to 14 hours before the "CAL" light goes
out when AC power is not applied.  So shipping to Cal Lab can be a problem
if it is a distance away, or you have to use a shipper like UPS or FEDEX and
you ship the night before and then use their "Morning delivery" and the Cal
Lab is expecting your 732A.  Same on the way back to you.  Of course you
could always strap another battery on the 732A and hook it up to the "ext
power" plug to last longer.  I have seen it done.  The issue is to get the
Cal Lab to charge the extra battery before they ship the 732A back to you.

    When you remove and work on the battery pack always have the AC power
plugged in.  The "CAL" led will stay on because the 18.6 v regulated supply
is working.

    The "CAL" light is to indicate that power has not been lost to the
Reference Amp or other associated circuits.  When the raw supply (battery)
voltage drops below about 21 volts the "CAL" light will go out.  Below that
voltage the heater circuits will not work correctly and the 18.6 volt
regulated supply will not regulate.  The requirement is that the Reference
Amp be kept "alive" at all times to maintain the output voltage that was
measured at the time of the most recent Calibration or Certification.  When
the semiconductor junctions are unbiased and cool off when power is lost,
and then power is restored the result will be a different 10 volts than
before the power failure.  My experience is that after all of the years that
these units have been powered up, this won't happen and when power is lost
and then restored, even months later, the 732A will come back to almost
exactly the same 10 volts as when they lost power, usually with in 0.2 PPM
after 24 hours of "warm up".

    What type of hookup leads are you using when measuring the 1 volt
output?  What is the PLC set to?  I always use 100 PLC to measure this.  If
you don't have "low thermal" connection leads you can experience uV changes
for a minute or more after plugging in the leads due to the "thermals"
generated because of the difference in temperature between the banana jacks
on the 732A and the banana plugs of the leads.  I have found that even just
plugging in the lead will generate a thermal difference because of
difference of temps and some heating due to the physical act of just
inserting the plug because of friction between the jack and plug (my theory
at any rate).  You have to allow at least a minute or more before being able
to make a measurement after plugging in the leads.  I just measured the
variation of the 1 volt output of my 732A and using my 3458A and I got a
total difference of  0.159 uV over 40 measurements using 100 PLC on the 1
volt range of the 3458A.  Using the MATH function and all of the data you
can collect.  That was after waiting for several minutes after plugging in
the leads.

    I hope all of this helps.

Bill



----- Original Message ----- 
From: "Randy Evans" <randyevans2688 at gmail.com>
To: "Discussion of precise voltage measurement" <volt-nuts at febo.com>
Sent: Friday, August 22, 2014 9:03 PM
Subject: 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 <tmicallef at 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 <randyevans2688 at 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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