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@gmail.com
wrote:

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@gmail.com wrote:

Randy,

I have replaced batteries in two units so far, which I bought on ebay (6V) and they fitted absolutelly perfect, no need to rework an metal and there was o isue with shortages. So there certainly are standard 6V batteries that fit without mods. I always try to keep things in original config, if possible.
Also, you do not want to adjust the 732a trimmers. It only gets unstable, if you are unlucky. I discussed this with some cal labs, same answer. What you could do is to adjust the jumper settings for coarse adjustment, if need be.
Adrian

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@gmail.com
To: "Discussion of precise voltage measurement" volt-nuts@febo.com
Sent: Friday, August 22, 2014 9:03 PM
Subject: Re: [volt-nuts] 732A and Prologix received

the

wrote:

tool

regardless

typically

use

them

had

on

https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts

Bill,

I have convinced myself that the problem I an seeing is due to thermals.
If I move the cables (with gold-plated banana plugs) using a small towel
rather than letting my hand touch the plugs, it is much more stable.  If I
then hold the banana plug with my hand after the reading has stabilized,
the reading drifts rapidly upward.  I am trying to check the stability of
the reading but I haven't figured out the MATH function yet.  I assume this
is a programmed function using GPIB only?

The stability I am seeing by manually recording readings (using NLPC of 100
and 1000) is much greater than what you are measuring on your system.  Not
sure how to ascertain if it's the 3458A or the 732.  The value of the
readings are very different between the two - the 3458 reads about 50 uV
high on the 10 V output and about 12 uV low on the 1V output.  Rather large
differences (this is after an ACAL).  I need to find some better cables to
make sure the errors are not due to thermals again.

Randy

On Sat, Aug 23, 2014 at 10:21 AM, Bill Gold wpgold3637@att.net wrote:

Bill,

I use a lot of the 12v 7ah batteries for my UPS backups and 732B. But yes,
I was mistaken. The 12V 5ah batteries are the ones that I am using in one
of my 732A. There is more play inside the tray with the 12v batteries by
several mm as compared to the 6v which only has a 2-3mm. The 12v conversion
is not difficult, but it is easier if the battery tray has already been
machined for the 12v batteries. The battery tabs don't line up well with
the existing holes and need to be widened. Two additional holes must also
be added.

Sourcing the batteries locally is more of a convenience than waiting for
the delivery. The el-cheapo 6v batteries are a waste of money and I have 8
batteries so far to prove it. They died the first time I had a 6hr outage
and would not hold a charge after that.

Todd

On Sat, Aug 23, 2014 at 1:21 PM, Bill Gold wpgold3637@att.net wrote:

Bill,

I have never been able to use banana plugs of any kind, with my 3458A,
due to their excessive thermal mass. I use 24 gauge wires to make a
twisted pair by hand with no connectors for precision voltage work. As
brought out in an earlier post by acbern, it doesn't matter about
plating or solder at least as long as your twisted pairs are made from
the same wire so the thermocouples balance out.

I am a big fan of M27500 shielded twisted pair wire for everyday use. It
is durable, heat resistant and capable of very low voltage use. The
insulator is Tefzel and the plating used to be silver but may be
something else now.  It take a few minutes work for proper termination
but it can be done for free. I tend to use a lot of the 24 gauge M27500
STP wire since it is fast to come to temperature, flexible and durable
enough to last quite awhile.
eBay always has quite a few small lengths available and Sierra Nevada
Products has a bunch of it. Sierra Nevada Products says that it is
Teflon but I think it may be Tefzel. I can help with termination
instructions if wanted.

Charlie

On 8/24/2014 7:22 AM, Randy Evans wrote:

Randy & all,

You have correctly concluded that some (maybe not all) of your measurement
problem is thermal EMF being added or subtracted in series within your
measurement interconnect. This thermal EMF is generated at the junction of
dissimilar metals when accompanied with thermal gradients between the test
lead and device terminals. You have to eliminate both the dissimilarity of
the metal junctions as well as minimize the thermal differences. The
terminals of the 3458A as well as the 732A are Beryllium Copper so you want
to use the same test lead terminals. Forget the typical Tin plated lugs or
even Gold plated as both are not Beryllium Copper and constitute dissimilar
metals. The best solution (as usually the most expensive) is to use a set of
Fluke 5440A-7005 (48") cables. I also have just as good results using the
much more flexible Pomona 11174A (lugs end always stay connected to the
732A) or 11058A with more convenient shielded banana plugs. The Fluke cable
has the added Guard built in but be sure to also use a Guard lead with the
Pomona cabled. The Guard lead does not need to be low thermal EMF. DIY
cables is usually not a good idea because the lead wire to terminal also
constitutes just as critical of junction. The above cables use Tellurium
Copper wire which is usually hard to find and hard to crimp properly and
NEVER solder.

As you observed, merely the friction of plugging in the spring banana plug
and heat transfer from your fingers will require ~3-5 minutes to stabilize.
Low mass terminals help with the time to initially stabilize but is not best
if dealing with local air current drafts that upset the instantaneous
thermal gradients between the higher mass device terminal and the lower mass
lead terminal. This issue is a trade-off and is specifically considered in
the Fluke cables but being careful with localized drafts around the
terminals during critical measurements can virtually eliminate this error
source.

I have attached an ~30-hour measurement run that I consistently do that
should give you some idea of expected measurement drift over time. Virtually
all of the measurement drift is due to the 3458A internal temperature
differences around the 7V reference caused by ambient temperature change.
The drift associated with the 732A is probably about 2-magnitudes less at
this ambient temp drift. In my situation, the inferred ambient temperature
is cycling with the home air-conditioning. Note the initial calibration
temperatures as well as the ACal temperatures and where the 3458A is
measuring exactly 10V. My primary 732A has been powered without loss for 4
years and >5 years before that. The 3458A is Agilent (Loveland) Cal'ed
yearly and is powered 24-7-365 except for the occasional mains power loss.
The graphical measurements is using a homegrown Agilent VEE program.

Don Johnson

-----Original Message-----
From: volt-nuts-bounces@febo.com [mailto:volt-nuts-bounces@febo.com] On
Behalf Of Randy Evans
Sent: Sunday, August 24, 2014 9:22 AM
To: Discussion of precise voltage measurement
Subject: Re: [volt-nuts] 732A and Prologix received

Bill,

I have convinced myself that the problem I an seeing is due to thermals.
If I move the cables (with gold-plated banana plugs) using a small towel
rather than letting my hand touch the plugs, it is much more stable.  If I
then hold the banana plug with my hand after the reading has stabilized, the
reading drifts rapidly upward.  I am trying to check the stability of the
reading but I haven't figured out the MATH function yet.  I assume this is a
programmed function using GPIB only?

The stability I am seeing by manually recording readings (using NLPC of 100
and 1000) is much greater than what you are measuring on your system.  Not
sure how to ascertain if it's the 3458A or the 732.  The value of the
readings are very different between the two - the 3458 reads about 50 uV
high on the 10 V output and about 12 uV low on the 1V output.  Rather large
differences (this is after an ACAL).  I need to find some better cables to
make sure the errors are not due to thermals again.

Randy

On Sat, Aug 23, 2014 at 10:21 AM, Bill Gold wpgold3637@att.net wrote:

to the "thermals"

weekend.

volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to
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and follow the instructions there.

Todd:

I check the batteries every month per the 732A manual.  Usually I keep a

few used cells from previous packs around that seem to be ok after checking
them for capacity just like checking the battery pack.  I can usually spot
cells going bad with that method.  If I don't have a spare set then I just
substitute a used cell until I receive a new set.

I agree with you that the cheap ones are crap.  I have used Power Sonic

a lot with some a few EaglePicher and one set of Enersys.  The EaglePicher
are crap so I will never use them.  EaglePicher have had a couple out of 8
that have failed very early.  I have never tried Panasonic.  So I stick with
the Power Sonic's.  I am not sure why the 12 volt ones would be better than
the 6 volts because 12 volt is just 6 lead acid cells while the 6volt are 3
lead acid cells.  If one of the 6 cells in the 12 volt battery go bad then
the whole battery has to be changed.  So you better buy good quality 12 volt
batteries.

I just can't seem to source batteries locally easily at a reasonable

price.  So I order them from Allied usually.

Bill

----- Original Message -----
From: "Todd Micallef" tmicallef@gmail.com
To: "Discussion of precise voltage measurement" volt-nuts@febo.com
Sent: Sunday, August 24, 2014 8:13 AM
Subject: Re: [volt-nuts] 732A and Prologix received

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https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts