[volt-nuts] 732A and Prologix received

Sun Aug 24 10:22:06 EDT 2014

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 at att.net> wrote:

> 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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