Fluke 732A Questions
Joe,
I live in Florida and searched for cal labs here that could do the job of
calibrating references. Lockheed Martin in Orlando is certified, but may not
have the best uncertainties. Fluke shows 0.3uV/V where LM shows 0.35uV/V.
Tektronix in Orlando also offers calibration, but they ship it out and it
turns out to be 0.38uV/V at the Keithley Primary Standards lab in Ohio. You
would be better shipping it yourself to Fluke.
I think Fluke is the best choice, but at least there are other options.
Todd
Joe wrote:
Where did you find the resistance of the thermistor 'as shipped'? I saw
mention of being supplied to the original owner when shipped as well
It was recorded on the original factory cal certificate. I have the
original certificates for two of mine. The others had rear panel
stickers applied by their original owner (a cal lab).
A properly working, good example should hold 0.1 ppm or better year
in, year out. I've seen some that do not meet that, but lots of them
do. I'm not aware of any other non-JJ standard that can match it,
including most 732Bs. (Some folks think 732As are generally better
than 732Bs because they are older and, thus, more stable because
better aged. I think there is more to it -- many 732Bs are plenty
old enough to have settled down to that level if they are ever going
to, but even the older 732Bs don't, in general, seem to exhibit quite
the stability of the 732As.)
Best regards,
Charles
Hi,
Are you guys adjusting your 732As?
I have a friend that works in a large CAL lab and he told me to never adjust my 732As, just compare them.
They send out their 732 Bs to Fluke but are never adjusted, just compared and sent back with current voltage reading ??
Thanks - Jeff
----- Original Message -----
From: "Charles Steinmetz" csteinmetz@yandex.com
To: "Discussion of precise voltage measurement" volt-nuts@febo.com
Sent: Tuesday, December 31, 2013 9:56:37 AM
Subject: Re: [volt-nuts] Fluke 732A Questions
Joe wrote:
Where did you find the resistance of the thermistor 'as shipped'? I saw
mention of being supplied to the original owner when shipped as well
It was recorded on the original factory cal certificate. I have the
original certificates for two of mine. The others had rear panel
stickers applied by their original owner (a cal lab).
A properly working, good example should hold 0.1 ppm or better year
in, year out. I've seen some that do not meet that, but lots of them
do. I'm not aware of any other non-JJ standard that can match it,
including most 732Bs. (Some folks think 732As are generally better
than 732Bs because they are older and, thus, more stable because
better aged. I think there is more to it -- many 732Bs are plenty
old enough to have settled down to that level if they are ever going
to, but even the older 732Bs don't, in general, seem to exhibit quite
the stability of the 732As.)
Best regards,
Charles
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and follow the instructions there.
The obvious reason for that suggestion is the adjustment
pot is likely to be noisy and is likely to introduce
uncertainty.
The big question that comes to my mind is if you care about
that level of uncertainty, why not replace the pot with a
voltage divider made of some low thermal coefficient fixed
value resistors?
-Chuck Harris
jeffhook@comcast.net wrote:
Hi,
Are you guys adjusting your 732As?
I have a friend that works in a large CAL lab and he told me to never adjust my
732As, just compare them.
They send out their 732 Bs to Fluke but are never adjusted, just compared and sent
back with current voltage reading ??
Thanks - Jeff
Any thing you do other than record the current voltage reading will
introduce more uncertainty and increase drift unless you have a defect.
Replacing a defective part will start the aging process over again for that
part. Do not change anything if you can help it.
Agilent is a good cal lab to use as well. They will run it for a few days
and take readings a few different times and give you a report.
Most of the time the battery is not enough to keep the box hot until they
plug it in so they count on warming up a few days.
Hope that helps.
John
On Tue, Dec 31, 2013 at 3:31 PM, Chuck Harris cfharris@erols.com wrote:
The obvious reason for that suggestion is the adjustment
pot is likely to be noisy and is likely to introduce
uncertainty.
The big question that comes to my mind is if you care about
that level of uncertainty, why not replace the pot with a
voltage divider made of some low thermal coefficient fixed
value resistors?
-Chuck Harris
jeffhook@comcast.net wrote:
Hi,
Are you guys adjusting your 732As?
I have a friend that works in a large CAL lab and he told me to never
adjust my
732As, just compare them.
They send out their 732 Bs to Fluke but are never adjusted, just compared
and sent
back with current voltage reading ??
Thanks - Jeff
volt-nuts mailing list -- volt-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/
mailman/listinfo/volt-nuts
and follow the instructions there.
--
John Phillips
Joe:
The NIST notes can be downloaded from this site.
https://archive.org/details/NISTTechNotes
Here is the battery check paragraph. I check mine once and month and plot performance using Excel.
2-47. OPERATION ON BATTERY
2-48. Prior to operating the 732A on battery power, the following procedure should be followed.
1. Connect a voltmeter at the rear terminal POWER INPUT jack to monitor the battery voltage.
2. Note the voltage while the battery is on trickle charge (the AC PWR LED is on, but BTRY CHG off).
The voltage should be around 27V.
3. Disconnect the line cord, wait 10 minutes, and then monitor the battery voltage for one-half hour.
The battery package may have to be replaced if the voltage decrease by more than 0.2V during
this period and the load represented by the 732A is correct ( see Section 4, Battery Discharge).
2-49. It may be advisable to perform the above procedure periodically to ensure battery backup capability is maintained.
While the Fluke manual maintains that the battery life is 24 hours, the reality is that you can get maybe 12 to 15 hours on a fresh set of cells. I think that the engineers didn't figure on the total heater current being around 240 ma in the final design. The batteries are rated at 4 AH and some simple math says that 4/.24 = 16.67 hours to a battery voltage of 5.25 V. But the "In Cal" LED will turn off around 22 volts so maybe 15 hours at best. The batteries will continue to supply heater current so it might keep the +18.6 volt regulator working for a few more hours, but when the batteries are down that far it is hard to calculate remaining life. This is why there is a Fluke 732A-7003 Transport Case and Battery Charger and you can have up to 4 battery packs in the case. This gives you a total of 72 hours transport time, according to Fluke. I have seen people take a couple of 12 volt high capacity SLA and duct tape them to the top of the 732A to increase transport time. I am not too sure what the AH capacity is of the 12 volts cells. I would guess that 12 AH might do the job but I have never gone that far to figure out.
The 24 hour spec is probably based upon the NIST Technical Note #1239 (Solid-State Voltage Standard Performance and design Guidelines) which recommended at least 24 hours of battery life for transport. You can get this from the same website as above.
I never had to worry about this (battery life) as Fluke used to have a repair and cal facility in Milpitas, CA and I worked in Morgan Hill, CA. I would either hand carry the unit to be certified, or Fluke would pick it up and deliver it back, under power. Then Fluke decided to sell the whole operation to FLW Service Corp who finally dropped the whole operation around 2005. I also retired around that time so I didn't care to pay for all of this myself ( I was having the Company pay ). Since then I have not had a "Certification" of any 732A units and just relied upon the inter-comparison method to hopefully keep a reasonable value of the "Volt". I have looked around the South SF Bay Area for a Cal Lab who could "Certifiy" one of my units and the only place I could find would be Simco in Sunnyvale. I will have to ask them what they charge for a "Certitication" of a 732A. The local Fluke place used to charge $500 but then that was using 732As that they had sent into Fluke in Everett WA. But then since this is just a hobby anymore I don't need, and didn't need while I was working, the full blown services and accuracy of Fluke in Everett. I guess a 732B would be a way to get all of this but who needs it right now, not me. Of course I could always get my own Josephson Junction but then I would be a real crazy "Volt Nut" and certifiable at the same time.
I have never even heard about the Fluke 735C until I saw one on fleabay, and I assume you were the one who bought this when I saw you asking about schematics.
Happy New Year
Bill
----- Original Message -----
From: "J. L. Trantham" jltran@att.net
To: "'Discussion of precise voltage measurement'" volt-nuts@febo.com
Sent: Monday, December 30, 2013 6:28 PM
Subject: Re: [volt-nuts] Fluke 732A Questions
Bill,
Sounds like you are further along in the 'volt-nut' process than I am. I'll
have to chase down the NIST paper. I have been very impressed by the
stability of the 732A and the 735C.
Unfortunately, I don't have any documentation on the 735C and only the early
manual for the 732A.
I would be interested in the specifics of the battery check procedure in
your manual. Unfortunately, my manual does not have a page 2-9.
I note that there are two banana jacks on the front of the battery module,
both black, one connected to ground and the other not connected to anything.
Any idea of what they are for?
I always like to keep equipment as 'original' as possible. If I can't find
the correct connector, I'll find something similar that will fit in the same
hole and use it instead. We'll see what I hear from Fluke and Hypertronics.
Also, how do you get your 732A calibrated? Do the batteries last long
enough to ship overnight to a facility?
Thanks for the info.
Joe
-----Original Message-----
From: volt-nuts-bounces@febo.com [mailto:volt-nuts-bounces@febo.com] On
Behalf Of Bill Gold
Sent: Monday, December 30, 2013 7:03 PM
To: Discussion of precise voltage measurement
Subject: Re: [volt-nuts] Fluke 732A Questions
Joe:
My 732A units vary in thermistor resistance from 3.408K ohms to 4.514K
ohms and have been extremely stable to with in +/- 5 ohms for years now. I
did measure the oven temperature of the one with the 3.408K ohms just to see
what was causing the thermistor resistance to be a little low and came up
with about 47 degrees centigrade, as best as my equipment would allow me to
measure it. Equipment was a Fluke 80TK thermocouple module, a Fluke 80 PK-1
thermocouple bead and a HP 3456A DVM. I put shrink wrap around the bead and
then threaded the bead into the temperature oven through one of the
adjustment holes in the front panel and made sure that it was far into the
oven, probably around the middle. Then I checked another unit that read
4.5K ohms and it read around 43 degrees C so all of that made sense. I
believe I saw somewhere that the spec was 45 degrees C +/- 2 C.
I did have to change the jumpers on the "Calibration PCB Assembly" on
one of my units so that it would match other 732A units that were "In Cal"
and had certified values. But that unit has since drifted down at a rate of
around 1.2 ppm per year which is with in specs but a little more than I have
seen from other units. Recently this unit has suddenly quit drifting down
and seems a lot more stable now. That was S/N 459xxxx. I have a S/N
343xxxx which has been proven rock solid for years now at around +/- .3 ppm
and just seems to have "DC noise" stability as it just goes up a little and
then down a little and never needed any adjustment. I also have a S/N
460xxxx which is extremely stable also. So I guess that age does seem to
factor into stability as well as how long they have been powered up. But
the only way to insure that you have a good "volt" is to have at least 4
units and then inter-compare them periodically following NIST (NBS)
Technical Note #430. While 430 was written for Saturated Standard Cells,
the technique seems to work just fine at 10 volts also. You can also find
this measurement technique in the 1st Fluke "Calibration - Philosophy in
Practice" book published around 1974.
I gave up on the "unobtainium" connector on the back of the battery pack
very quickly. I drilled a 1/4 " holes on either side of the "unobtainium"
connector, after removing it, and used two single miniature banana jacks to
allow me to connect to the batteries for the purpose of checking their
performance as described in the 732A manual page 2-9 in manual P/N 788414
May 1986. I should probably turn in my resignation as a "volt nut" for this
action but it works. KISS.
Bill
----- Original Message -----
From: "J. L. Trantham" jltran@att.net
To: volt-nuts@febo.com
Sent: Saturday, December 28, 2013 2:51 PM
Subject: [volt-nuts] Fluke 732A Questions
I have reviewed the prior postings on Volt-nuts (a very rewarding review,
BTW)) regarding the 732A and have two questions:
-
Has anyone determined the part number, or a source, for the
mating
plug to J10, the external power connector for the 732A-7005 battery pack?
I
noted some postings recently about this but did not find a definitive
response regarding the identity of this plug. The alternative would
appear
to be a complete replacement of J10 and its plug, as long is it all fits
in
the opening in the panel. I hate to 'bore holes' in vintage equipment.
-
The oven thermistor in my 'new to me' unit measures 4229 ohms
(+/-
an ohm or two) after the unit has warmed up for a week or so. I note the
manual refers to 3K to 4K for the value of this thermistor when the unit
is
'stable' as well as other's posting values in the mid 3500's ohms for
their
units. Should I be concerned? The unit seems to be stable to within
about
2 uV over about a week (as measured by my 3458A - see below). Should I
open
the unit and try to measure the oven temperature or just be satisfied that
the unit seems to be working?
I had to replace the four 6V 4AH SLA batteries and they charged up
appropriately as judged by the front panel LED's. I had to remove the
'jumper' for the '40' option on the A7 board and connect the jumper to the
'20' and '10' options (total of '30') in order to get the unit to adjust
to
10.0000000 VDC on my 'Agilent In Cal'd' 3458A.
The need to change the jumpers, perhaps, could be just an ageing issue or,
on the other hand, a 'temperature' issue with the oven.
Should I open the unit and directly measure the temperature (supposedly
about 48 degrees C) or just be satisfied with what I have?
My recently added 735C also needed moving some 'jumpers' in order to get
it
'on scale', as determined by my 3458A, although it's thermistor measures
about 3330 ohms (after being on for several weeks).
Thanks for everyone's help.
Joe
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Jeff,
Too late.
I have already moved the jumpers and adjusted all of the front panel adjustments to achieve the desired output voltages.
Since I don't have any 'historical' data about the performance of my specific unit, I will 'start from scratch' on the unit I now have. Whether to send it out for calibration or just keep it, adjusted by the 3458A, and watch from now on is the issue.
I don't have enough data to decide about long term stability at this point but I am gaining valuable information about how long it will last on batteries and how to go about preparing it for shipment for calibration if I go that way.
Thanks for the input.
Joe
-----Original Message-----
From: volt-nuts-bounces@febo.com [mailto:volt-nuts-bounces@febo.com] On Behalf Of jeffhook@comcast.net
Sent: Tuesday, December 31, 2013 5:23 PM
To: Discussion of precise voltage measurement
Subject: Re: [volt-nuts] Fluke 732A Questions
Hi,
Are you guys adjusting your 732As?
I have a friend that works in a large CAL lab and he told me to never adjust my 732As, just compare them.
They send out their 732 Bs to Fluke but are never adjusted, just compared and sent back with current voltage reading ??
Thanks - Jeff
----- Original Message -----
From: "Charles Steinmetz" csteinmetz@yandex.com
To: "Discussion of precise voltage measurement" volt-nuts@febo.com
Sent: Tuesday, December 31, 2013 9:56:37 AM
Subject: Re: [volt-nuts] Fluke 732A Questions
Joe wrote:
Where did you find the resistance of the thermistor 'as shipped'? I
saw mention of being supplied to the original owner when shipped as
well
It was recorded on the original factory cal certificate. I have the original certificates for two of mine. The others had rear panel stickers applied by their original owner (a cal lab).
A properly working, good example should hold 0.1 ppm or better year in, year out. I've seen some that do not meet that, but lots of them do. I'm not aware of any other non-JJ standard that can match it, including most 732Bs. (Some folks think 732As are generally better than 732Bs because they are older and, thus, more stable because better aged. I think there is more to it -- many 732Bs are plenty old enough to have settled down to that level if they are ever going to, but even the older 732Bs don't, in general, seem to exhibit quite the stability of the 732As.)
Best regards,
Charles
volt-nuts mailing list -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts
and follow the instructions there.
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and follow the instructions there.
Bill,
I have yet to put my 732A though it's paces but I could connect an external
power supply, disconnect the AC supply and the battery module and slowly
decrease the supplied voltage and see what happens when.
I'll try your measurement algorithm for the battery to see when the 'IN CAL'
LED goes out and what the current draws are. If the measured voltage at J10
is 27 V, then the actual battery voltage should be about 27.6 V, accounting
for the diode in the circuit (unless the current draw during measurement is
so low that no voltage drop occurs across the diode).
I found the NIST/NBS Tech Note easily.
I think if I decide to send it out for calibration, I'll use Fluke, if they
still calibrate the unit. I'll call them later this week of next week to
see what services/accessories they might still have available.
Yes, I wound up with the 735C. It was easy to replace the NiCd battery pack
and bring it 'on scale' by adjusting the 'jumpers' and the front panel
adjustment. I now only have to deal with the periodic 'NO CAL' LED
indication. I need to study the 732A manual then take a close look at the
735C to see how it works on it.
This also brings up the question of 'low EMF cables' for accurate
measurement. I have a Fluke 720A K/V Divider on the shelf that I have yet
to bring out to check to see if it is operational. Another one of those
'projects' for a later time.
Where would one look for 'low EMF cables' to be used in precise measurement
experiments and what errors might one expect to find using Pomona gold
plated Banana Plug cables (which is as good as I have at this time)?
Thanks for the info.
Happy New Year to all.
Joe
-----Original Message-----
From: volt-nuts-bounces@febo.com [mailto:volt-nuts-bounces@febo.com] On
Behalf Of Bill Gold
Sent: Tuesday, December 31, 2013 6:26 PM
To: Discussion of precise voltage measurement
Subject: Re: [volt-nuts] Fluke 732A Questions
Joe:
The NIST notes can be downloaded from this site.
https://archive.org/details/NISTTechNotes
Here is the battery check paragraph. I check mine once and month and
plot performance using Excel.
2-47. OPERATION ON BATTERY
2-48. Prior to operating the 732A on battery power, the following procedure
should be followed.
1. Connect a voltmeter at the rear terminal POWER INPUT jack to monitor
the battery voltage.
2. Note the voltage while the battery is on trickle charge (the AC PWR
LED is on, but BTRY CHG off).
The voltage should be around 27V.
3. Disconnect the line cord, wait 10 minutes, and then monitor the
battery voltage for one-half hour.
The battery package may have to be replaced if the voltage decrease
by more than 0.2V during
this period and the load represented by the 732A is correct ( see
Section 4, Battery Discharge).
2-49. It may be advisable to perform the above procedure periodically to
ensure battery backup capability is maintained.
While the Fluke manual maintains that the battery life is 24 hours, the
reality is that you can get maybe 12 to 15 hours on a fresh set of cells. I
think that the engineers didn't figure on the total heater current being
around 240 ma in the final design. The batteries are rated at 4 AH and some
simple math says that 4/.24 = 16.67 hours to a battery voltage of 5.25 V.
But the "In Cal" LED will turn off around 22 volts so maybe 15 hours at
best. The batteries will continue to supply heater current so it might keep
the +18.6 volt regulator working for a few more hours, but when the
batteries are down that far it is hard to calculate remaining life. This is
why there is a Fluke 732A-7003 Transport Case and Battery Charger and you
can have up to 4 battery packs in the case. This gives you a total of 72
hours transport time, according to Fluke. I have seen people take a couple
of 12 volt high capacity SLA and duct tape them to the top of the 732A to
increase transport time. I am not too sure what the AH capacity is of the
12 volts cells. I would guess that 12 AH might do the job but I have never
gone that far to figure out.
The 24 hour spec is probably based upon the NIST Technical Note #1239
(Solid-State Voltage Standard Performance and design Guidelines) which
recommended at least 24 hours of battery life for transport. You can get
this from the same website as above.
I never had to worry about this (battery life) as Fluke used to have a
repair and cal facility in Milpitas, CA and I worked in Morgan Hill, CA. I
would either hand carry the unit to be certified, or Fluke would pick it up
and deliver it back, under power. Then Fluke decided to sell the whole
operation to FLW Service Corp who finally dropped the whole operation around
2005. I also retired around that time so I didn't care to pay for all of
this myself ( I was having the Company pay ). Since then I have not had a
"Certification" of any 732A units and just relied upon the inter-comparison
method to hopefully keep a reasonable value of the "Volt". I have looked
around the South SF Bay Area for a Cal Lab who could "Certifiy" one of my
units and the only place I could find would be Simco in Sunnyvale. I will
have to ask them what they charge for a "Certitication" of a 732A. The
local Fluke place used to charge $500 but then that was using 732As that
they had sent into Fluke in E verett WA. But then since this is just a
hobby anymore I don't need, and didn't need while I was working, the full
blown services and accuracy of Fluke in Everett. I guess a 732B would be a
way to get all of this but who needs it right now, not me. Of course I
could always get my own Josephson Junction but then I would be a real crazy
"Volt Nut" and certifiable at the same time.
I have never even heard about the Fluke 735C until I saw one on fleabay,
and I assume you were the one who bought this when I saw you asking about
schematics.
Happy New Year
Bill
----- Original Message -----
From: "J. L. Trantham" jltran@att.net
To: "'Discussion of precise voltage measurement'" volt-nuts@febo.com
Sent: Monday, December 30, 2013 6:28 PM
Subject: Re: [volt-nuts] Fluke 732A Questions
Bill,
Sounds like you are further along in the 'volt-nut' process than I am.
I'll
have to chase down the NIST paper. I have been very impressed by the
stability of the 732A and the 735C.
Unfortunately, I don't have any documentation on the 735C and only the
early
manual for the 732A.
I would be interested in the specifics of the battery check procedure in
your manual. Unfortunately, my manual does not have a page 2-9.
I note that there are two banana jacks on the front of the battery module,
both black, one connected to ground and the other not connected to
anything.
Any idea of what they are for?
I always like to keep equipment as 'original' as possible. If I can't
find
the correct connector, I'll find something similar that will fit in the
same
hole and use it instead. We'll see what I hear from Fluke and
Hypertronics.
Also, how do you get your 732A calibrated? Do the batteries last long
enough to ship overnight to a facility?
Thanks for the info.
Joe
-----Original Message-----
From: volt-nuts-bounces@febo.com [mailto:volt-nuts-bounces@febo.com] On
Behalf Of Bill Gold
Sent: Monday, December 30, 2013 7:03 PM
To: Discussion of precise voltage measurement
Subject: Re: [volt-nuts] Fluke 732A Questions
Joe:
My 732A units vary in thermistor resistance from 3.408K ohms to 4.514K
ohms and have been extremely stable to with in +/- 5 ohms for years now.
I
did measure the oven temperature of the one with the 3.408K ohms just to
see
what was causing the thermistor resistance to be a little low and came up
with about 47 degrees centigrade, as best as my equipment would allow me
to
measure it. Equipment was a Fluke 80TK thermocouple module, a Fluke 80
PK-1
thermocouple bead and a HP 3456A DVM. I put shrink wrap around the bead
and
then threaded the bead into the temperature oven through one of the
adjustment holes in the front panel and made sure that it was far into the
oven, probably around the middle. Then I checked another unit that read
4.5K ohms and it read around 43 degrees C so all of that made sense. I
believe I saw somewhere that the spec was 45 degrees C +/- 2 C.
I did have to change the jumpers on the "Calibration PCB Assembly" on
one of my units so that it would match other 732A units that were "In Cal"
and had certified values. But that unit has since drifted down at a rate
of
around 1.2 ppm per year which is with in specs but a little more than I
have
seen from other units. Recently this unit has suddenly quit drifting down
and seems a lot more stable now. That was S/N 459xxxx. I have a S/N
343xxxx which has been proven rock solid for years now at around +/- .3
ppm
and just seems to have "DC noise" stability as it just goes up a little
and
then down a little and never needed any adjustment. I also have a S/N
460xxxx which is extremely stable also. So I guess that age does seem to
factor into stability as well as how long they have been powered up. But
the only way to insure that you have a good "volt" is to have at least 4
units and then inter-compare them periodically following NIST (NBS)
Technical Note #430. While 430 was written for Saturated Standard Cells,
the technique seems to work just fine at 10 volts also. You can also find
this measurement technique in the 1st Fluke "Calibration - Philosophy in
Practice" book published around 1974.
I gave up on the "unobtainium" connector on the back of the battery
pack
very quickly. I drilled a 1/4 " holes on either side of the "unobtainium"
connector, after removing it, and used two single miniature banana jacks
to
allow me to connect to the batteries for the purpose of checking their
performance as described in the 732A manual page 2-9 in manual P/N 788414
May 1986. I should probably turn in my resignation as a "volt nut" for
this
action but it works. KISS.
Bill
----- Original Message -----
From: "J. L. Trantham" jltran@att.net
To: volt-nuts@febo.com
Sent: Saturday, December 28, 2013 2:51 PM
Subject: [volt-nuts] Fluke 732A Questions
I have reviewed the prior postings on Volt-nuts (a very rewarding
review,
BTW)) regarding the 732A and have two questions:
-
Has anyone determined the part number, or a source, for the
mating
plug to J10, the external power connector for the 732A-7005 battery
pack?
I
noted some postings recently about this but did not find a definitive
response regarding the identity of this plug. The alternative would
appear
to be a complete replacement of J10 and its plug, as long is it all fits
in
the opening in the panel. I hate to 'bore holes' in vintage equipment.
-
The oven thermistor in my 'new to me' unit measures 4229 ohms
(+/-
an ohm or two) after the unit has warmed up for a week or so. I note
the
manual refers to 3K to 4K for the value of this thermistor when the unit
is
'stable' as well as other's posting values in the mid 3500's ohms for
their
units. Should I be concerned? The unit seems to be stable to within
about
2 uV over about a week (as measured by my 3458A - see below). Should I
open
the unit and try to measure the oven temperature or just be satisfied
that
the unit seems to be working?
I had to replace the four 6V 4AH SLA batteries and they charged up
appropriately as judged by the front panel LED's. I had to remove the
'jumper' for the '40' option on the A7 board and connect the jumper to
the
'20' and '10' options (total of '30') in order to get the unit to adjust
to
10.0000000 VDC on my 'Agilent In Cal'd' 3458A.
The need to change the jumpers, perhaps, could be just an ageing issue
or,
on the other hand, a 'temperature' issue with the oven.
Should I open the unit and directly measure the temperature (supposedly
about 48 degrees C) or just be satisfied with what I have?
My recently added 735C also needed moving some 'jumpers' in order to get
it
'on scale', as determined by my 3458A, although it's thermistor measures
about 3330 ohms (after being on for several weeks).
Thanks for everyone's help.
Joe
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Joe,
I don't have any history on my 732As either. M y 3458As & 2002 are out of cal too so I'm running blind with all my stuff :o)
I'm hoping to find a cheap 732B and have my CAL lab buddy sneak it into work and do a poor mans cal on it. (hard to do with a 732A)
He does this each year with my L&N 4214 10K standards but he's getting close to retirement. I wish Fluke had a cheap cal for the hobbyist - Jeff
----- Original Message -----
From: "J. L. Trantham" jltran@att.net
To: "Discussion of precise voltage measurement" volt-nuts@febo.com
Sent: Tuesday, December 31, 2013 7:01:32 PM
Subject: Re: [volt-nuts] Fluke 732A Questions
Jeff,
Too late.
I have already moved the jumpers and adjusted all of the front panel adjustments to achieve the desired output voltages.
Since I don't have any 'historical' data about the performance of my specific unit, I will 'start from scratch' on the unit I now have. Whether to send it out for calibration or just keep it, adjusted by the 3458A, and watch from now on is the issue.
I don't have enough data to decide about long term stability at this point but I am gaining valuable information about how long it will last on batteries and how to go about preparing it for shipment for calibration if I go that way.
Thanks for the input.
Joe
Joe:
A correction on the dropout voltage when the "In Cal" light goes out, I
found my notes and it is 21 volts instead of 22 volts. The way I did this
was to remove the battery pack, AC voltage and then just feed in a power
supply where the battery pack would have delivered it's voltage to the
back-plane mother board. Then I just reduced the voltage until the light
turned off. So that means that Fluke was following the battery
manufacturers specs of 5.25 volts at the end of the discharge curve.
The banana jacks on the battery pack have two jobs. One is to provide a
very good chassis ground to the battery pack and the other is probably to
guide the pack accurately into the mother board. One other thing I have
found out the hard way is that the holes in the top plate of the battery
pack where the battery terminals come through are very close to the battery
terminals and can short out to the chassis. I have made the holes a LOT
bigger to avoid this problem. This really depends upon the brand of
batteries you are using but after having to repair the regulator board I
would rather be safe than sorry.
I have 6 Pomona 1756-48 low thermal leads for when I need to be careful
with thermals. I also have made my own "low thermal" (I think) using
Pomona 4892 gold plated double banana plugs and Belden 9272 twisted pair
twinax, using a Pomona 1825 for the ground lead. If I need single banana
plugs to connect to the 732A I use Pomona 4897 gold plated. I know that
this isn't the best possible low thermal because the wire is tin plated but
I have looked and I can't find a good source of bare copper twisted pair
shielded wire. When I am making measurements with the home made cables I
just wait a few minutes for the thermals to settle down. Why Belden 9272?
It was the best choice from what was available at work. From what I have
seen Pomona was acquired by Fluke and makes special low thermal cables for
Fluke that are not available through the Pomona catalog.
When you find out from Fluke what services they offer and prices please
let all of us know.
Bill
----- Original Message -----
From: "J. L. Trantham" jltran@att.net
To: "'Discussion of precise voltage measurement'" volt-nuts@febo.com
Sent: Tuesday, December 31, 2013 5:13 PM
Subject: Re: [volt-nuts] Fluke 732A Questions
Bill,
I have yet to put my 732A though it's paces but I could connect an
external
power supply, disconnect the AC supply and the battery module and slowly
decrease the supplied voltage and see what happens when.
I'll try your measurement algorithm for the battery to see when the 'IN
CAL'
LED goes out and what the current draws are. If the measured voltage at
J10
is 27 V, then the actual battery voltage should be about 27.6 V,
accounting
for the diode in the circuit (unless the current draw during measurement
is
so low that no voltage drop occurs across the diode).
I found the NIST/NBS Tech Note easily.
I think if I decide to send it out for calibration, I'll use Fluke, if
they
still calibrate the unit. I'll call them later this week of next week to
see what services/accessories they might still have available.
Yes, I wound up with the 735C. It was easy to replace the NiCd battery
pack
and bring it 'on scale' by adjusting the 'jumpers' and the front panel
adjustment. I now only have to deal with the periodic 'NO CAL' LED
indication. I need to study the 732A manual then take a close look at the
735C to see how it works on it.
This also brings up the question of 'low EMF cables' for accurate
measurement. I have a Fluke 720A K/V Divider on the shelf that I have yet
to bring out to check to see if it is operational. Another one of those
'projects' for a later time.
Where would one look for 'low EMF cables' to be used in precise
measurement
experiments and what errors might one expect to find using Pomona gold
plated Banana Plug cables (which is as good as I have at this time)?
Thanks for the info.
Happy New Year to all.
Joe