Re: [volt-nuts] fluke 731b battery pack

[Christopher Brown]

If even with a fully charged pack the batt charge side gets high enough
to feed into the ref you need to check the current value of the current
limiting resistor in the charge circuit.

Don't have the exact details in my head at the moment (was about 3 years
ago) but in both of my 731Bs that resistor had dropped in value by more
than a little and was floating the batteries at a higher voltage.  I
replaced with a correct value over-rated metal film type and no more
issue, max floating voltage for ~ C/20 maint to the pack is below cutoff.

If it is climbing high enough compared to the other feed, then resistors
have drifted and the batt circuit is running to hot or the filter AC ->
ref supply is running too low.

On 8/3/16 13:30, Orin Eman wrote:
> On Wed, Aug 3, 2016 at 2:08 PM, David  wrote:
> 
>>
>> I looked at the schematic and is seems feasible without excessive
>> effort.  Either the existing simple series preregulator can be
>> modified or replaced allowing it to both charge the battery (through a
>> blocking diode) and power the instrument or a completely separate
>> power charging circuit can be added in parallel.
>>
> 
> 
> The existing charging circuit _is_ in parallel with the pre-regulator; they
> are separated by CR5 and CR6 and the pre-regulator/battery outputs are
> combined by CR8 and CR9.  The only problem with the existing circuit is
> with a fresh, strong, fully charged battery pack, charging pulses will leak
> past CR8 with only R1/C1 to filter them.
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[volt-nuts] fluke 731b battery pack

[Mark Sims]

Most NiMH cells have a capacity of around twice what a NiCad has,  so a NiCad 
charger that works at a C/10 charge rate will be charging NiMH cells at C/20.   
That can be an acceptable trickle rate for NiMH cells, but I prefer something 
in the C/40 neighborhood.  I put some in an electric shaver (really crude 
charger) and they last longer than NiCads.


Proper low self discharge NiMh cells have about 1/10th the self-discharge rate 
of NiCads.   I have some in some test equipment that seldom gets used and after 
over a year of storage were still going strong and provided hours of run time.  
 NiCads would be dead after a couple of months of storage.
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Re: [volt-nuts] fluke 731b battery pack

[Tom Miller]

If they are integrated with the device, the manufacturer must certify they 
have tested the device and proved it can not cause a fire. If you change the 
NiCd battery to a LiFe system, you will fail that requirement. When you 
ship, you must certify there is no hazmat item in your package. There is a 
minimum Wh capacity allowed but I am not sure what it is. Not much from 
memory.







- Original Message - 
From: "David" <davidwh...@gmail.com>

To: "Discussion of precise voltage measurement" <volt-nuts@febo.com>
Sent: Wednesday, August 03, 2016 5:29 PM
Subject: Re: [volt-nuts] fluke 731b battery pack



Does that restriction apply to batteries which are integrated with a
device?  I thought it only applied to separate cells.

On Wed, 03 Aug 2016 17:20:00 -0400, you wrote:

I like the LiFe idea except for the restrictions on shipping by air or 
USPS.


That shouldn't be too much of a problem for most that have access to a 
local

cal lab.

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Re: [volt-nuts] fluke 731b battery pack

[David]

On Wed, 3 Aug 2016 14:30:33 -0700, you wrote:

>On Wed, Aug 3, 2016 at 2:08 PM, David  wrote:
>
>>
>> I looked at the schematic and is seems feasible without excessive
>> effort.  Either the existing simple series preregulator can be
>> modified or replaced allowing it to both charge the battery (through a
>> blocking diode) and power the instrument or a completely separate
>> power charging circuit can be added in parallel.
>
>The existing charging circuit _is_ in parallel with the pre-regulator; they
>are separated by CR5 and CR6 and the pre-regulator/battery outputs are
>combined by CR8 and CR9.  The only problem with the existing circuit is
>with a fresh, strong, fully charged battery pack, charging pulses will leak
>past CR8 with only R1/C1 to filter them.

Ah, I did not see that A1S1A is the same as switch A1S1B; I am used to
seeing a little dashed line connecting all of the elements of a single
switch.  I guess that goes along with the symbol they used for
constant current diode CR10 which I have not seen in a long time.

Anyway, the changes I suggested still apply.  Actually, using a
battery which accepts a constant voltage charge simplifies the
requirements.
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Re: [volt-nuts] fluke 731b battery pack

[Orin Eman]

On Wed, Aug 3, 2016 at 2:08 PM, David  wrote:

>
> I looked at the schematic and is seems feasible without excessive
> effort.  Either the existing simple series preregulator can be
> modified or replaced allowing it to both charge the battery (through a
> blocking diode) and power the instrument or a completely separate
> power charging circuit can be added in parallel.
>


The existing charging circuit _is_ in parallel with the pre-regulator; they
are separated by CR5 and CR6 and the pre-regulator/battery outputs are
combined by CR8 and CR9.  The only problem with the existing circuit is
with a fresh, strong, fully charged battery pack, charging pulses will leak
past CR8 with only R1/C1 to filter them.
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Re: [volt-nuts] fluke 731b battery pack

[David]

Does that restriction apply to batteries which are integrated with a
device?  I thought it only applied to separate cells.

On Wed, 03 Aug 2016 17:20:00 -0400, you wrote:

>I like the LiFe idea except for the restrictions on shipping by air or USPS.
>
>That shouldn't be too much of a problem for most that have access to a local 
>cal lab.
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Re: [volt-nuts] fluke 731b battery pack

[Tom Miller]

I like the LiFe idea except for the restrictions on shipping by air or USPS.

That shouldn't be too much of a problem for most that have access to a local 
cal lab.





- Original Message - 
From: "David" <davidwh...@gmail.com>

To: "Discussion of precise voltage measurement" <volt-nuts@febo.com>
Sent: Wednesday, August 03, 2016 5:08 PM
Subject: Re: [volt-nuts] fluke 731b battery pack



On Wed, 3 Aug 2016 16:34:31 -0400, you wrote:


Eric wrote:


NiMH cells seem to work in the 731b so I'd prefer to use them over NiCd
because of the higher capacity and lower toxicity of potential leaks. Is
there a downside to doing this?


In my experience, good NiCDs are preferable to NiMHs.  Good NiCds have
substantially lower self-leakage than NiMHs (this is true even of the
"NEW!! Low-discharge!!" NiMHs).  NiCds also don't degrade nearly as fast
if they are left too long on trickle charge.   Both of these features
translate directly into increased life for the NiCds.  NiCds are also
quieter, and capable of larger current drains, due to their lower
internal (series) resistance (high current is not really an issue in
your application).


That is my experience as well however I do like the better low
discharge NiMH cells.  Some are better than other though.


Consumer-type NiCds may suffer from the problem PHK noted (poor quality
due to low production volumes), but there are still many industrial and
military applications that specify NiCDs for some or all of the reasons
given above.  Excellent NiCds are readily available -- just look for
aerospace-grade parts rather than consumer batteries.


Low leakage and high temperature NiCd cells seem to last a lot longer
than other types and you will not find any consumer versions of these
but the price is high.


Many built-in charging circuits are crude and leave the batteries on a
trickle current that is really too high, particularly given the
temperatures inside electronic instruments.  So whichever batteries you
choose, plan on redesigning the charging circuit.

That brings up the possibility of using either LiFePO4 or SLA (sealed
lead-acid) batteries -- if you have to redesign the charging circuit
anyway, you can just as easily design it for LiFePO4 or SLA.

I have not evaluated the 731B power supply in particular, but LiFePO4
would be my presumptive choice unless I encountered an insurmountable
obstacle.

Best regards,

Charles


I looked at the schematic and is seems feasible without excessive
effort.  Either the existing simple series preregulator can be
modified or replaced allowing it to both charge the battery (through a
blocking diode) and power the instrument or a completely separate
power charging circuit can be added in parallel.

The difficulty of maintaining charge in a backup application using
NiMH cells would lead me to consider LiFePO4 cells instead.  The only
serious difficulty would be preventing excessive discharge which will
ruin a lithium (or PbSO4) based rechargeable battery in short order.
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Re: [volt-nuts] fluke 731b battery pack

[Orin Eman]

The battery in the 731B is charged via a diode and 510 ohm resistor from
the rectified DC, before the smoothing capacitor.  The smoothing capacitor
and power supply is fed by another diode, so the battery is charged with a
pulse waveform.

If you have no battery, then this pulse charge waveform will get around the
power supply regulator (since the regulated supply and battery are diode
switched) and increase noise on the output.  I therefore don't recommend
running without a battery installed... (though you could remove CR5 or or
R30).

Even with the battery installed, if it's good, at full charge, you can
still get charging pulses bypassing the regulator.  I built a high-side
switch to switch between the battery and power supply on my 731B.

I got the local Batteries Plus to build a new battery pack.  They usually
have NiCd cells of the right size and will build a battery pack while you
wait.  With an NiCd pack so easily available, I saw no reason to change
battery type.

Orin.

On Wed, Aug 3, 2016 at 1:34 PM, Charles Steinmetz 
wrote:

> Eric wrote:
>
> NiMH cells seem to work in the 731b so I'd prefer to use them over NiCd
>> because of the higher capacity and lower toxicity of potential leaks. Is
>> there a downside to doing this?
>>
>
> In my experience, good NiCDs are preferable to NiMHs.  Good NiCds have
> substantially lower self-leakage than NiMHs (this is true even of the
> "NEW!! Low-discharge!!" NiMHs).  NiCds also don't degrade nearly as fast if
> they are left too long on trickle charge.   Both of these features
> translate directly into increased life for the NiCds.  NiCds are also
> quieter, and capable of larger current drains, due to their lower internal
> (series) resistance (high current is not really an issue in your
> application).
>
> Consumer-type NiCds may suffer from the problem PHK noted (poor quality
> due to low production volumes), but there are still many industrial and
> military applications that specify NiCDs for some or all of the reasons
> given above.  Excellent NiCds are readily available -- just look for
> aerospace-grade parts rather than consumer batteries.
>
> Many built-in charging circuits are crude and leave the batteries on a
> trickle current that is really too high, particularly given the
> temperatures inside electronic instruments.  So whichever batteries you
> choose, plan on redesigning the charging circuit.
>
> That brings up the possibility of using either LiFePO4 or SLA (sealed
> lead-acid) batteries -- if you have to redesign the charging circuit
> anyway, you can just as easily design it for LiFePO4 or SLA.
>
> I have not evaluated the 731B power supply in particular, but LiFePO4
> would be my presumptive choice unless I encountered an insurmountable
> obstacle.
>
> Best regards,
>
> Charles
>
>
>
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Re: [volt-nuts] fluke 731b battery pack

[David]

On Wed, 3 Aug 2016 16:34:31 -0400, you wrote:

>Eric wrote:
>
>> NiMH cells seem to work in the 731b so I'd prefer to use them over NiCd
>> because of the higher capacity and lower toxicity of potential leaks. Is
>> there a downside to doing this?
>
>In my experience, good NiCDs are preferable to NiMHs.  Good NiCds have 
>substantially lower self-leakage than NiMHs (this is true even of the 
>"NEW!! Low-discharge!!" NiMHs).  NiCds also don't degrade nearly as fast 
>if they are left too long on trickle charge.   Both of these features 
>translate directly into increased life for the NiCds.  NiCds are also 
>quieter, and capable of larger current drains, due to their lower 
>internal (series) resistance (high current is not really an issue in 
>your application).

That is my experience as well however I do like the better low
discharge NiMH cells.  Some are better than other though.

>Consumer-type NiCds may suffer from the problem PHK noted (poor quality 
>due to low production volumes), but there are still many industrial and 
>military applications that specify NiCDs for some or all of the reasons 
>given above.  Excellent NiCds are readily available -- just look for 
>aerospace-grade parts rather than consumer batteries.

Low leakage and high temperature NiCd cells seem to last a lot longer
than other types and you will not find any consumer versions of these
but the price is high.

>Many built-in charging circuits are crude and leave the batteries on a 
>trickle current that is really too high, particularly given the 
>temperatures inside electronic instruments.  So whichever batteries you 
>choose, plan on redesigning the charging circuit.
>
>That brings up the possibility of using either LiFePO4 or SLA (sealed 
>lead-acid) batteries -- if you have to redesign the charging circuit 
>anyway, you can just as easily design it for LiFePO4 or SLA.
>
>I have not evaluated the 731B power supply in particular, but LiFePO4 
>would be my presumptive choice unless I encountered an insurmountable 
>obstacle.
>
>Best regards,
>
>Charles

I looked at the schematic and is seems feasible without excessive
effort.  Either the existing simple series preregulator can be
modified or replaced allowing it to both charge the battery (through a
blocking diode) and power the instrument or a completely separate
power charging circuit can be added in parallel.

The difficulty of maintaining charge in a backup application using
NiMH cells would lead me to consider LiFePO4 cells instead.  The only
serious difficulty would be preventing excessive discharge which will
ruin a lithium (or PbSO4) based rechargeable battery in short order.
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Re: [volt-nuts] fluke 731b battery pack

[Tom Miller]

NiMH does not do too well in float charge conditions and that is the main 
state a 731B will spend its time.


Regards,
Tom

- Original Message - 
From: "Eric Garner" <garn...@gmail.com>

To: "Discussion of precise voltage measurement" <volt-nuts@febo.com>
Sent: Wednesday, August 03, 2016 1:27 PM
Subject: [volt-nuts] fluke 731b battery pack



So I managed to get one of the Fluke 731b's mentioned on the list a while
back. It was a little more chewed up than the description in the auction
led me to believe:

https://plus.google.com/u/0/112871219575380932919/posts/iDWyzwYYRdj?pid=6314634305601690930=112871219575380932919

but it appears to be functional.

The NiCd pack appears to have leaked some time in the past and was 
removed,

which is fine since I was going to replace the batteries anyway.

Looking through the archives, replacement battery packs for the 731b has
been a popular topic but I have some questions that remain open.

1. NiMH cells seem to work in the 731b so I'd prefer to use them over NiCd
because of the higher capacity and lower toxicity of potential leaks. Is
there a downside to doing this?

2. If I go with NiMH, is there a manufacturer that's prefered? reading
reviews of NiMH cells online leads me to believe that some manufacturers
(Tenergy) have lower quality and are less reliable.

3. If I go with NiCd would you expect problems if I used larger cells 
(4/5A

vs 2/3A)




thanks

--Eric
_
Eric Garner
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Re: [volt-nuts] fluke 731b battery pack

[David]

Are the low discharge NiMH cells available now any more rugged than
regular NiCd cells as far as charging current?

One solution I would consider is using LiFePO4 cells and modifying the
charger for current limited constant voltage.

On Wed, 03 Aug 2016 19:37:12 +, you wrote:

>
>In message 

Re: [volt-nuts] fluke 731b battery pack

[Bill Gold]

Eric:

I have been using NiMH AA batteries in my 731B for at least 15 years
now.  I am sure that the specs say don't use them in a circuit designed for
NiCd but I haven't had any problems with over heating or overcharging.  You
have to do some mods to the battery mounting to get them in there but once
done you are good for a lifetime.  I have never checked to see how long the
NiMH batteries would run for but my guess would be longer than the original
NiCds.

Bill

- Original Message - 
From: "Eric Garner" <garn...@gmail.com>
To: "Discussion of precise voltage measurement" <volt-nuts@febo.com>
Sent: Wednesday, August 03, 2016 10:27 AM
Subject: [volt-nuts] fluke 731b battery pack


> So I managed to get one of the Fluke 731b's mentioned on the list a while
> back. It was a little more chewed up than the description in the auction
> led me to believe:
>
>
https://plus.google.com/u/0/112871219575380932919/posts/iDWyzwYYRdj?pid=6314634305601690930=112871219575380932919
>
> but it appears to be functional.
>
> The NiCd pack appears to have leaked some time in the past and was
removed,
> which is fine since I was going to replace the batteries anyway.
>
> Looking through the archives, replacement battery packs for the 731b has
> been a popular topic but I have some questions that remain open.
>
> 1. NiMH cells seem to work in the 731b so I'd prefer to use them over NiCd
> because of the higher capacity and lower toxicity of potential leaks. Is
> there a downside to doing this?
>
> 2. If I go with NiMH, is there a manufacturer that's prefered? reading
> reviews of NiMH cells online leads me to believe that some manufacturers
> (Tenergy) have lower quality and are less reliable.
>
> 3. If I go with NiCd would you expect problems if I used larger cells
(4/5A
> vs 2/3A)
>
>
>
>
> thanks
>
> --Eric
> _
> Eric Garner
> ___
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[volt-nuts] fluke 731b battery pack

[Eric Garner]

So I managed to get one of the Fluke 731b's mentioned on the list a while
back. It was a little more chewed up than the description in the auction
led me to believe:

https://plus.google.com/u/0/112871219575380932919/posts/iDWyzwYYRdj?pid=6314634305601690930=112871219575380932919

but it appears to be functional.

The NiCd pack appears to have leaked some time in the past and was removed,
which is fine since I was going to replace the batteries anyway.

Looking through the archives, replacement battery packs for the 731b has
been a popular topic but I have some questions that remain open.

1. NiMH cells seem to work in the 731b so I'd prefer to use them over NiCd
because of the higher capacity and lower toxicity of potential leaks. Is
there a downside to doing this?

2. If I go with NiMH, is there a manufacturer that's prefered? reading
reviews of NiMH cells online leads me to believe that some manufacturers
(Tenergy) have lower quality and are less reliable.

3. If I go with NiCd would you expect problems if I used larger cells (4/5A
vs 2/3A)




thanks

--Eric
_
Eric Garner
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[volt-nuts] Fluke 731b Rack Mounting

[David Garrido]

Hello All,

I just picked up a 731b that I would like to mount in a rack with a back up 
UPS.  I know that Fluke made the "Rack Mounting Kit M03-205-605"

These were used to house up to four of these standards in the space of 3U, I 
think.

The present day version of this is the Fluke 734a-7001.

Does anyone know where to find one of these older rack options or know if the 
present day 734a would fit the older 731b standards?

Cheers,

David
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Re: [volt-nuts] Fluke 731B

[John Phillips]

I would never adjust any pots on a working fluke voltage standard. When the
pot moves you introduce more drift.
Just keep track of differences.
By the same token I do not turn off my 3458As as long as the line power is
up.
There was a time I had a rack of 15 3458As running waiting to be sold.
We have a power outage about 1 time per year long enough to trip our julian
date and time clock. We use it to track power up time.

I do not see anyone posting 3458A in stat mode data: mean, SDEV, High, and
Low, Range, and Number of samples over extended time.
then reverse polarity and do it again.
Also DC cal values before and after Auto cal and Keysight cal would be nice
to know.
Also using Before and after cal data from Keysight to correct values.
Do not adjust the Flukes  but keep a spreadsheet of best guess of its value.
Something like  mean of present guess + before cal data correction + after
cal data correction.
Example:
Say you present guess (guess1) is 9.468 cal the meter using 9.468
and then read the cal var 1 (I think that is the one for the reference
board)
Your as found data should indicate how far off your reference is.  correct
and call that guess2
After you get the meter back read cal var 1 and then use successive
approximation to when caling to get the same value in var 1. That should be
guess3
So new guess is mean (guess1, guess2, guess3).
If you have better confidence in one guess or less confidence in an other
the values could be weighted.
You never really know what the actual value is  a given time but do know it
is changing.  You can guess at it's value like 9.468 is just a guess
even if the real value is 9.4681 or even 9.468 with what we have
you just cannot know for sure. There can alway be another digit.

Anyone want to poke some holes in what I wrote?
Does anyone have a better way to come up with a Cal value for a fluke 10
volt reference without sending it out for calibration?
Where could send it to get a better calibration and what would it cost?


On Thu, Mar 26, 2015 at 8:03 PM, J. L. Trantham jlt...@att.net wrote:

 A couple of years ago, I sat my 735C, a (at that time) recently Agilent
 calibrated 3458A, and two 731B's on a bench and have left the references
 on, with battery back-up for any power failure.  I have turned the 3458A
 off and on a number of times in the interim.

 When I set all this up, I adjusted the 735C to 10.00 VDC as best I
 could using the then recently calibrated 3458A and adjusted the 731B's to
 match the 735C using the 3458A as a 'null' meter.

 Tonight, after the 3458A had been on for several weeks, I did the 'AutoCal
 All' on the 3458A and read each of the references.

 The 735C measures about 10.16 VDC, and the 731B's measure about
 10.05 VDC each, within about 2 uV of each other.

 In the next couple of months, I plan to send the 3458A back to
 Agilent/Keysight for recalibration and see what the meter measures 'as
 received' and 'as left'.

 We'll see how close it is to being 'in tolerance' 'as received'.

 Hope this helps.

 Joe

 -Original Message-
 From: volt-nuts [mailto:volt-nuts-boun...@febo.com] On Behalf Of Orin Eman
 Sent: Monday, March 23, 2015 12:36 AM
 To: Discussion of precise voltage measurement
 Cc: richiem5...@gmail.com
 Subject: Re: [volt-nuts] Fluke 731B

 Richard,

 Some really good information has already been posted.  Here is what I have
 found.

 I posted a comparison of the 731B against the Geller Labs SVR-T here:


 http://www.eevblog.com/forum/testgear/geller-labs-svr-and-svr-t/msg282582/#msg282582

 There were within 1ppm of each other over 48 hours and 3.8 deg K.

 I'm currently running a comparison against the reference from an HP 3458A,
 using an Agilent 34461A in _ratio_ mode.  A screen capture follows if the
 list lets it through.  There is only 5 hours here as I just updated the
 34461A firmware (it adds another digit to the scaling limits on the trend
 chart and is definitely worthwhile).

 One thing about the 731B is that it if the NiCd pack is dead or fully
 charged(!), there will be much more noise on the output.  I designed a
 'high-side' switch to switch between AC and battery power and it improves
 noise when the NiCd is fully charged.  (The original design is a diode
 switch and if you have a NiCd pack which has a high voltage when fully
 charged, the half-wave rectified AC that is used to charge the NiCd pack
 leaks through to the voltage reference power supply.)

 A big WARNING.  If a 731B still has its NiCd pack installed, replace it.
 I had Batteries Plus make me a replacement pack.  About $30 as I recall.
 If the NiCd pack isn't installed, you need to remove the diode that goes
 from the battery pack to the voltage reference supply, or you'll get
 unfiltered half-wave rectified AC on your voltage reference power supply
 and it does get into the output!

 My 731B seems to be doing quite well IMO, being within 1ppm of the new at
 the time Geller SVR-T.  It has also been

Re: [volt-nuts] Fluke 731B

[J. L. Trantham]

John,

Thanks for the thoughts.  I basically agree with the idea of not 'adjusting' 
the standards but when I got them, they all had 'problems', including leaking 
NiCd batteries that required clean up.  Not knowing how long they had been off 
and having only calibrated DMM's (3458A and 7081) I chose to get the standards 
up and running then 'adjust' them to begin a 'new era' of standards, at least 
in my set-up.

I also have two 732A's that have been brought back to life and they are sitting 
on now for about 12 to 18 months.  I have not tried to read them in a while.

I have been collecting other gear including Fluke 720A, 721A, 750A, and 752A 
and a Fluke 845AB.  I also have a Fluke 887AB that I need to get working.  My 
problem is that work is about 80 to 100 hours per week and I have little time 
to spend on this.  But, once retired.

I have left my 3458A's on for extended periods of time (weeks) and have been 
very pleased that when I turn them back on after weeks off, they come back 
within a couple of uV to the last readings of the 735C suggesting everything is 
fairly stable or at least drifting at the same rate and in the same direction.

I'm a bit nervous about leaving the 3458A's on all the time due to the 
potential for the displays to fade or fail.  So far, that's not been a problem.

As far as calibration of the Fluke references, I would think Fluke would be the 
best bet but there is the problem of getting them there and back while still 
powered.  I've been working on a method to do that using SLA batteries or using 
the Fluke 732A-7003 battery charger/pack.  I think Fluke made a case that would 
house the 732A and the 732A-7003, both filled with batteries and completely 
charged, to ship the units in for calibration.  My plan is to construct a 
'case' to house two 12V 18AH SLA's and a charger that can be plugged in once 
the unit arrives at the calibration facility.

I have acquired a couple of dead, industrial strength, UPS's that, once I get 
some time, I would like to rebuild and power my 'metrology section' with to 
deal with any power interruptions.  I have a stand-by generator system as well. 
 However, it all takes time to get up and running and I don't have much of that 
right now.

Joe

-Original Message-
From: volt-nuts [mailto:volt-nuts-boun...@febo.com] On Behalf Of John Phillips
Sent: Friday, March 27, 2015 1:41 AM
To: Discussion of precise voltage measurement
Subject: Re: [volt-nuts] Fluke 731B

I would never adjust any pots on a working fluke voltage standard. When the pot 
moves you introduce more drift.
Just keep track of differences.
By the same token I do not turn off my 3458As as long as the line power is up.
There was a time I had a rack of 15 3458As running waiting to be sold.
We have a power outage about 1 time per year long enough to trip our julian 
date and time clock. We use it to track power up time.

I do not see anyone posting 3458A in stat mode data: mean, SDEV, High, and Low, 
Range, and Number of samples over extended time.
then reverse polarity and do it again.
Also DC cal values before and after Auto cal and Keysight cal would be nice to 
know.
Also using Before and after cal data from Keysight to correct values.
Do not adjust the Flukes  but keep a spreadsheet of best guess of its value.
Something like  mean of present guess + before cal data correction + after cal 
data correction.
Example:
Say you present guess (guess1) is 9.468 cal the meter using 9.468 and 
then read the cal var 1 (I think that is the one for the reference
board)
Your as found data should indicate how far off your reference is.  correct and 
call that guess2 After you get the meter back read cal var 1 and then use 
successive approximation to when caling to get the same value in var 1. That 
should be
guess3
So new guess is mean (guess1, guess2, guess3).
If you have better confidence in one guess or less confidence in an other the 
values could be weighted.
You never really know what the actual value is  a given time but do know it is 
changing.  You can guess at it's value like 9.468 is just a guess even if 
the real value is 9.4681 or even 9.468 with what we have you just 
cannot know for sure. There can alway be another digit.

Anyone want to poke some holes in what I wrote?
Does anyone have a better way to come up with a Cal value for a fluke 10 volt 
reference without sending it out for calibration?
Where could send it to get a better calibration and what would it cost?


On Thu, Mar 26, 2015 at 8:03 PM, J. L. Trantham jlt...@att.net wrote:

 A couple of years ago, I sat my 735C, a (at that time) recently 
 Agilent calibrated 3458A, and two 731B's on a bench and have left the 
 references on, with battery back-up for any power failure.  I have 
 turned the 3458A off and on a number of times in the interim.

 When I set all this up, I adjusted the 735C to 10.00 VDC as best I 
 could using the then recently calibrated 3458A and adjusted

Re: [volt-nuts] Fluke 731B

[J. L. Trantham]

A couple of years ago, I sat my 735C, a (at that time) recently Agilent 
calibrated 3458A, and two 731B's on a bench and have left the references on, 
with battery back-up for any power failure.  I have turned the 3458A off and on 
a number of times in the interim.

When I set all this up, I adjusted the 735C to 10.00 VDC as best I could 
using the then recently calibrated 3458A and adjusted the 731B's to match the 
735C using the 3458A as a 'null' meter.

Tonight, after the 3458A had been on for several weeks, I did the 'AutoCal All' 
on the 3458A and read each of the references.

The 735C measures about 10.16 VDC, and the 731B's measure about 10.05 
VDC each, within about 2 uV of each other.

In the next couple of months, I plan to send the 3458A back to Agilent/Keysight 
for recalibration and see what the meter measures 'as received' and 'as left'.

We'll see how close it is to being 'in tolerance' 'as received'.

Hope this helps.

Joe

-Original Message-
From: volt-nuts [mailto:volt-nuts-boun...@febo.com] On Behalf Of Orin Eman
Sent: Monday, March 23, 2015 12:36 AM
To: Discussion of precise voltage measurement
Cc: richiem5...@gmail.com
Subject: Re: [volt-nuts] Fluke 731B

Richard,

Some really good information has already been posted.  Here is what I have 
found.

I posted a comparison of the 731B against the Geller Labs SVR-T here:

http://www.eevblog.com/forum/testgear/geller-labs-svr-and-svr-t/msg282582/#msg282582

There were within 1ppm of each other over 48 hours and 3.8 deg K.

I'm currently running a comparison against the reference from an HP 3458A, 
using an Agilent 34461A in _ratio_ mode.  A screen capture follows if the list 
lets it through.  There is only 5 hours here as I just updated the 34461A 
firmware (it adds another digit to the scaling limits on the trend chart and is 
definitely worthwhile).

One thing about the 731B is that it if the NiCd pack is dead or fully 
charged(!), there will be much more noise on the output.  I designed a 
'high-side' switch to switch between AC and battery power and it improves noise 
when the NiCd is fully charged.  (The original design is a diode switch and if 
you have a NiCd pack which has a high voltage when fully charged, the half-wave 
rectified AC that is used to charge the NiCd pack leaks through to the voltage 
reference power supply.)

A big WARNING.  If a 731B still has its NiCd pack installed, replace it.  I had 
Batteries Plus make me a replacement pack.  About $30 as I recall.  If the NiCd 
pack isn't installed, you need to remove the diode that goes from the battery 
pack to the voltage reference supply, or you'll get unfiltered half-wave 
rectified AC on your voltage reference power supply and it does get into the 
output!

My 731B seems to be doing quite well IMO, being within 1ppm of the new at the 
time Geller SVR-T.  It has also been reading 9.6 to 9.7 on the 34461A 
for the last year (as long as I don't turn on the 8568A that is next to the 
34461A... the 8568A blows warm air into the 34461A and then all bets are off).

Orin.

[image: Inline image 1]

On Sat, Mar 21, 2015 at 1:02 PM, Richard Moore richiem5...@gmail.com
wrote:

 Hi all — realisitcally, what sort of stability can be expected from a 
 fully functional 731B regarding variation in ambient temp a few 
 degrees C around 23, and for long-term drift?

 Fluke’s specs are very conservative, and I think the 731 is far better 
 than the specs would lead you to believe, but I have no practical 
 experience with these units.
 ___
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Re: [volt-nuts] Fluke 731B

[Orin Eman]

Richard,

Some really good information has already been posted.  Here is what I have
found.

I posted a comparison of the 731B against the Geller Labs SVR-T here:

http://www.eevblog.com/forum/testgear/geller-labs-svr-and-svr-t/msg282582/#msg282582

There were within 1ppm of each other over 48 hours and 3.8 deg K.

I'm currently running a comparison against the reference from an HP 3458A,
using an Agilent 34461A in _ratio_ mode.  A screen capture follows if the
list lets it through.  There is only 5 hours here as I just updated the
34461A firmware (it adds another digit to the scaling limits on the trend
chart and is definitely worthwhile).

One thing about the 731B is that it if the NiCd pack is dead or fully
charged(!), there will be much more noise on the output.  I designed a
'high-side' switch to switch between AC and battery power and it improves
noise when the NiCd is fully charged.  (The original design is a diode
switch and if you have a NiCd pack which has a high voltage when fully
charged, the half-wave rectified AC that is used to charge the NiCd pack
leaks through to the voltage reference power supply.)

A big WARNING.  If a 731B still has its NiCd pack installed, replace it.  I
had Batteries Plus make me a replacement pack.  About $30 as I recall.  If
the NiCd pack isn't installed, you need to remove the diode that goes from
the battery pack to the voltage reference supply, or you'll get unfiltered
half-wave rectified AC on your voltage reference power supply and it does
get into the output!

My 731B seems to be doing quite well IMO, being within 1ppm of the new at
the time Geller SVR-T.  It has also been reading 9.6 to 9.7 on the
34461A for the last year (as long as I don't turn on the 8568A that is next
to the 34461A... the 8568A blows warm air into the 34461A and then all bets
are off).

Orin.

[image: Inline image 1]

On Sat, Mar 21, 2015 at 1:02 PM, Richard Moore richiem5...@gmail.com
wrote:

 Hi all — realisitcally, what sort of stability can be expected from a
 fully functional 731B regarding variation in ambient temp a few degrees C
 around 23, and for long-term drift?

 Fluke’s specs are very conservative, and I think the 731 is far better
 than the specs would lead you to believe, but I have no practical
 experience with these units.
 ___
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 To unsubscribe, go to
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[volt-nuts] Fluke 731B power switch replacement: TE Connectivity / Alcoswitch MTL206N

[Christopher Brown]

Original was MSTL206N, count not cross-ref the maker.

TE MTL206N is an exact match drop-in, same locking toggle with same
shape/size everything.

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Re: [volt-nuts] Fluke 731B parts xref

[WB6BNQ]

Hi Fred,

Well, it seems to me that the only time the relay is an issue is if the coarse 
adjust pot is not fully clockwise.  If you look at the schematic, the relay is 
bypassed with R101 (coarse) is in the full CW position (a detented switch 
position) actuating S101.  Near as I can tell, the coarse CW position 
completely bypasses the protection circuit.  So, you should not
need batteries.

The coarse/fine controls are used when you have a fixed voltage source.  As you 
indicate you have 332 then you can adjust it and do not need the coarse/fine 
function.  Of course you would be responsible for making sure of INPUT / OUTPUT 
switches are set to the right scales for the voltages being used.

But let me make the standard disclaimer - - -  It has been a long time since I 
used my 750A - - - so I could be wrong !

Please let me know if I am all wet.

BillWB6BNQ



Fred Schneider wrote:

 I have a 750 too but it needs some rare 6 V batterys to make -6-0-+6V. The 
 adaption to 10V sounds interesting but i do have standard cells and like to 
 use it for that. I do not use the 750 at the moment because without the 
 batterys it won't work. You have an alernative solution for that too ?
 I measure the cells with a 10 GOhm 7,5 digit meter, write down the reading, 
 then zero the meter in the 1V range with that, set my 720 to that value and 
 connect the meter, then connect my 332 and set the 10V or 100V so the meter 
 reads zero again. And finaly undo the zero and measure the output of the 720 
 again to heck if the reading is the same as I wrote down.

 Fred PA4TIM

 Op 22 nov. 2012 om 07:43 heeft WB6BNQ wb6...@cox.net het volgende 
 geschreven:

  Hi Chris,
 
  If you study the schematic you will see that S3, the front panel 
  lock-open-momentary switch, is
  in series between the standard cell (J10) and the null meter (J8).  So what 
  is happening is the
  voltage from the 750A goes to one side of the null meter and the reference 
  (Standard Cell) goes
  to the other side of the null meter.
 
  Remove the wire from S1201 going to J7 and cover it with heat shrink.  Then 
  connect a wire
  between J7 and the 10 volt TAP (top of R12).  From this point on, the 
  Standard Cell banana
  jacks is where you connect the 731B 10 volt source, the null meter goes to 
  its jacks and the S3
  switch is still normal.  The kelvin decades for the 1.xx voltage are no 
  longer in the circuit and
  have no effect.
 
  Should you ever want to sell the 750A (you shouldn't) it is easy to reverse 
  back to the factory
  arrangement.  If you don't have a manual for the 750A, let me know and I 
  will forward it to you.
 
  BillWB6BNQ
 
 
 
  Christopher Brown wrote:
 
  On 11/21/12 6:44 PM, WB6BNQ wrote:
  Hi Chris,
 
  Do you mean the Fluke 750A ?  It has connections for standard cells.  The 
  752 is a ratio
  device designed to be used with a 10 volt reference standard.  No need 
  for the 1.xx outputs
  from the 731B or the use of standard cells..
 
  Your are correct, not the 752 (would like a 752 and a 720) but do have 2
  750A.
 
 
  The 750A standard cell arrangement can be bypassed and set up for use 
  with just a 10 volt
  reference using the original banana jacks for the reference and null 
  meter as normal.  All
  that is needed is to (non destructively) remove one connection and add 
  one wire.
 
  BillWB6BNQ
 
  That sounds like a very worthwhile mod.  How is it done and how does it
  change operation?
 
  As far as the 731B(s), I have 2.
 
  One is in good working order and overall great shape.  Came out of a
  standards lab in the czech republic that recently switched to a 732A.
 
  Have a replacement NiCd pack currently cycling.  Other than cleaning,
  and replacing the dead pack the only changes planned are replacing the
  IEC socket with a small filtered socket (have a box of them) and
  replacing R30 (if needed) to adjust the float current for the new pack
  (old is 450mah, new is 2100mah.
 
  For the second (received this morning), intend to do the same, and
  repair.  I may just hard-wire around the failed switch, but beyond that,
  not fixing it would just bug me.
 
  The ref board is in good shape and does not appear to have been messed
  with.  The main issues being the pot and the P/S section.
 
  Near as I can tell the Fairchild 1N5248B is a good match for CR1, and
  for 2 cents each I can just grab a batch and select.
 
  I have a bunch of 4148 and 1n914 fairchild parts around here somewhere,
  curious as to suggestion of 4448 over 4148?  Looks like 2pf v.s. 4pf and
  the 4148 may start conducting a few hundred mv earlier from the datasheet.
 
  Thanks
  Chris - WL7CLA
 
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Re: [volt-nuts] Fluke 731B parts xref

[Christopher Brown]

On 11/21/12 6:44 PM, WB6BNQ wrote:
 Hi Chris,
 
 Do you mean the Fluke 750A ?  It has connections for standard cells.  The 752 
 is a ratio
 device designed to be used with a 10 volt reference standard.  No need for 
 the 1.xx outputs
 from the 731B or the use of standard cells..

Your are correct, not the 752 (would like a 752 and a 720) but do have 2
750A.

 
 The 750A standard cell arrangement can be bypassed and set up for use with 
 just a 10 volt
 reference using the original banana jacks for the reference and null meter as 
 normal.  All
 that is needed is to (non destructively) remove one connection and add one 
 wire.
 
 BillWB6BNQ

That sounds like a very worthwhile mod.  How is it done and how does it
change operation?


As far as the 731B(s), I have 2.

One is in good working order and overall great shape.  Came out of a
standards lab in the czech republic that recently switched to a 732A.

Have a replacement NiCd pack currently cycling.  Other than cleaning,
and replacing the dead pack the only changes planned are replacing the
IEC socket with a small filtered socket (have a box of them) and
replacing R30 (if needed) to adjust the float current for the new pack
(old is 450mah, new is 2100mah.


For the second (received this morning), intend to do the same, and
repair.  I may just hard-wire around the failed switch, but beyond that,
not fixing it would just bug me.

The ref board is in good shape and does not appear to have been messed
with.  The main issues being the pot and the P/S section.


Near as I can tell the Fairchild 1N5248B is a good match for CR1, and
for 2 cents each I can just grab a batch and select.


I have a bunch of 4148 and 1n914 fairchild parts around here somewhere,
curious as to suggestion of 4448 over 4148?  Looks like 2pf v.s. 4pf and
the 4148 may start conducting a few hundred mv earlier from the datasheet.

Thanks
Chris - WL7CLA

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Re: [volt-nuts] Fluke 731B parts xref

[WB6BNQ]

Hi Chris,

If you study the schematic you will see that S3, the front panel 
lock-open-momentary switch, is
in series between the standard cell (J10) and the null meter (J8).  So what is 
happening is the
voltage from the 750A goes to one side of the null meter and the reference 
(Standard Cell) goes
to the other side of the null meter.

Remove the wire from S1201 going to J7 and cover it with heat shrink.  Then 
connect a wire
between J7 and the 10 volt TAP (top of R12).  From this point on, the Standard 
Cell banana
jacks is where you connect the 731B 10 volt source, the null meter goes to its 
jacks and the S3
switch is still normal.  The kelvin decades for the 1.xx voltage are no longer 
in the circuit and
have no effect.

Should you ever want to sell the 750A (you shouldn't) it is easy to reverse 
back to the factory
arrangement.  If you don't have a manual for the 750A, let me know and I will 
forward it to you.

BillWB6BNQ



Christopher Brown wrote:

 On 11/21/12 6:44 PM, WB6BNQ wrote:
  Hi Chris,
 
  Do you mean the Fluke 750A ?  It has connections for standard cells.  The 
  752 is a ratio
  device designed to be used with a 10 volt reference standard.  No need for 
  the 1.xx outputs
  from the 731B or the use of standard cells..

 Your are correct, not the 752 (would like a 752 and a 720) but do have 2
 750A.

 
  The 750A standard cell arrangement can be bypassed and set up for use with 
  just a 10 volt
  reference using the original banana jacks for the reference and null meter 
  as normal.  All
  that is needed is to (non destructively) remove one connection and add one 
  wire.
 
  BillWB6BNQ

 That sounds like a very worthwhile mod.  How is it done and how does it
 change operation?

 As far as the 731B(s), I have 2.

 One is in good working order and overall great shape.  Came out of a
 standards lab in the czech republic that recently switched to a 732A.

 Have a replacement NiCd pack currently cycling.  Other than cleaning,
 and replacing the dead pack the only changes planned are replacing the
 IEC socket with a small filtered socket (have a box of them) and
 replacing R30 (if needed) to adjust the float current for the new pack
 (old is 450mah, new is 2100mah.

 For the second (received this morning), intend to do the same, and
 repair.  I may just hard-wire around the failed switch, but beyond that,
 not fixing it would just bug me.

 The ref board is in good shape and does not appear to have been messed
 with.  The main issues being the pot and the P/S section.

 Near as I can tell the Fairchild 1N5248B is a good match for CR1, and
 for 2 cents each I can just grab a batch and select.

 I have a bunch of 4148 and 1n914 fairchild parts around here somewhere,
 curious as to suggestion of 4448 over 4148?  Looks like 2pf v.s. 4pf and
 the 4148 may start conducting a few hundred mv earlier from the datasheet.

 Thanks
 Chris - WL7CLA

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