[volt-nuts] 732A and Prologix received

acbern at gmx.de acbern at gmx.de
Tue Aug 26 20:41:53 EDT 2014 

hi randy,

just for curiosity, why doing 100 measurements at nplc 1000. is this to sample a changing value?
when i am doing 10 measurements from a stable signal at nplc 100 (only there many subsequent measuremnts with statistics make sense) I am already getting a stanard deviation below 0.1ppm.
in a 30 minute test cycle, i would also be concerned about drifts (acal) unless the amb. temperature is really very stable (half a degree already adds about 0.25ppm at 10v)

thanks




> Gesendet: Dienstag, 26. August 2014 um 04:23 Uhr
> Von: "Randy Evans" <randyevans2688 at gmail.com>
> An: "Discussion of precise voltage measurement" <volt-nuts at febo.com>
> Betreff: Re: [volt-nuts] 732A and Prologix received
>
> Is there any way to tell when the function key routine is complete?  In the
> case of taking multiple readings using the DEFKEY and MATH function, I
> don't see any indication when the routine is complete.  In one particular
> case, I am taking a 100 readings with NLPC set for 1000 so its a long while
> before it's complete, but i have to guess when it's done.
> 
> Thanks,
> 
> Randy
> 
> 
> On Sun, Aug 24, 2014 at 6:04 PM, Randy Evans <randyevans2688 at gmail.com>
> wrote:
> 
> > Bill,
> >
> > I am trying to figure out the MATH function without much success.  I input
> > the sequence you said (I looked up the instructions to understand what you
> > did - seems logical), BLUE DEFKEY BLUE F1 MATH 14;NRDGS 40;TRIG 4;TRIG; and
> > it shows up on the display when I input BLUE F1.  I hit ENTER and it takes
> > the 40 measurements and the MATH symbol shows on the display during the
> > measurements.  After the SMPL symbol no longer blinks I hit MATH 2 and I
> > get a MATH ERR symbol on the display.  I tried it a couple of times and the
> > same result so I am doing something wrong.  Is there a better source for
> > explaining how to do front panel masurements than the User Guide, which
> > seems oriented at programming automatic rather than manual measurements.
> >
> > Randy
> >
> >
> >
> > On Sun, Aug 24, 2014 at 4:46 PM, Bill Gold <wpgold3637 at att.net> wrote:
> >
> >> Randy:
> >>
> >>     The MATH function is accessible from the keypad.  I don't have an IEEE
> >> interface right now that works.  You can also program the numeric keypad
> >> keys to have preprogrammed functions.  DEFKEY
> >>
> >>     I have made my own "low thermal" measurement leads from Pomona #4892
> >> banana plugs and Belden #9272 wire.  Why 9272, because it was handy at the
> >> time.  It is tin plated copper, shielded twisted pair 20 ga.  I have plans
> >> to do custom cables with 16 ga. bare copper wire that I will twist and
> >> then
> >> put a braided shield over it.  I simply cannot find what I want so I will
> >> build my own cable.  I have done something like this before and it worked
> >> fine.  When I get a "round toit".
> >>
> >>     I have 6 ea. Pomona 1756-48 spade lug low thermal leads that I have
> >> used
> >> in the past to verify my homemade "low thermal" leads as described above.
> >> Frankly I cannot see any difference between using the 1756 cables and my
> >> homemade cables once I give them a few minutes for the thermals to go
> >> away.
> >> As far as I can tell and measure the differences, if any, are below 0.1
> >> ppm
> >> at 10 volts.
> >>
> >>     Since the 10 volt, 1.0 volt and 1.018 volt outputs on the 732A are all
> >> adjustable you may be seeing a misadjusted 1 volt from the 732A.  As far
> >> as
> >> the instability of the readings it is hard to determine which is causing
> >> the
> >> problem.  I have programed (DEFKEY) a numeric keypad key #1 with the
> >> following code.  "MATH 14;NRDGS 40;TRIG 4;TRIG ;"   So what this does is
> >> set
> >> the MATH to "Statistics" (store high reading/low reading/ and mean of the
> >> readings) in the registers, the number of readings to "40", the trigger to
> >> "hold" (which keeps the meter from triggering until I press "ENTER" and
> >> then
> >> trigger the sequence of 40 readings when I push the "ENTER" button.  You
> >> can
> >> do all of this manually from the keypads but since I use this sequence a
> >> lot
> >> I have preprogrammed it.  This is after I set digits to "8" and PLC to
> >> 100.
> >> Once those 40 readings are finished then you can access the various MATH
> >> statistic registers, using the menu, by entering "MATH" and then a 2 for
> >> low, a 4 for mean, and 13 for high.  Of course you could do all of this
> >> through the IEEE also.  The 3458A has a very rich set of measurement
> >> commands.  I am still learning all of them.  It depends upon what I am
> >> trying to accomplish.
> >>
> >>     Since the 1.018 and 1.0 volt outputs are passive and derived from
> >> resistive dividers from the 10 volt, I don't see how they could contribute
> >> to the varying readings you are measuring.  I think I would put a short on
> >> the input of the 3458A and manually set the range to 1 volt and then
> >> observe
> >> the variations that way without the 732A involved.  When I do this I see a
> >> variation from low reading to high reading of 0.125 uVolts and then
> >> another
> >> 40 I get 0.155 uVolts.  This is without the GUARD connected to the low
> >> side
> >> of the measurment terminals, GUARD connected doesn't seem to affect the
> >> readings.  So that is the base noise of the 3458A without the 732A,
> >> somewhere below .2uVolts.  When hooked up to the 732A 1.0 volt output I
> >> got
> >> a variation of 0.159 uVolts using the same 40 reading method above.  I
> >> would
> >> use this to determine where your problem might exist.  Just having the
> >> meter
> >> input shorted will point you in the right direction.  Meter, cables or
> >> 732A.
> >>
> >>     Sorry for the long dissertation.  Friends get mad at me for being so
> >> detailed sometimes.
> >>
> >> Bill
> >>
> >> ----- Original Message -----
> >> From: "Randy Evans" <randyevans2688 at gmail.com>
> >> To: "Discussion of precise voltage measurement" <volt-nuts at febo.com>
> >> Sent: Sunday, August 24, 2014 7:22 AM
> >> 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 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
> >> > > > > > _______________________________________________
> >> > > > > > volt-nuts mailing list -- volt-nuts at febo.com
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> >> > > > > >
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