Re: [volt-nuts] Calibration of voltage standards
To amplify Chuck's point,
The only meter worth considering, if you are going to get one, is the
FLUKE 845. Preferably, the battery operated version which has a higher
isolation leakage resistance. However, the 110
volt rack mount model would do just as equally.
Bill....WB6BNQ
Chuck Harris wrote:
To do a comparison of the sort you are asking about, the
sensitivity of the null meter is much more important than
its ultimate accuracy.
So, neither of your meters is really the right meter to
use for this task. What you want is called a null meter,
and is generally sensitive to the microvolt region.
-Chuck Harris
Ken Peek wrote:
Hi Group,
I have heard of a few different ways to measure one 10V voltage standard
against another 10V voltage standard.
Assume we have two 10V voltage standards. One is calibrated, the other
not only needs to be calibrated, but probably adjusted. For the sake of
simplicity, let's say the two standards are Fluke 732B's.
I think the best way is to connect the two units' (-) terminals
together, then connect a calibrated meter in between the (+) terminals,
and measure the difference. I have also heard that to remove thermal
EMFs, you should use a low-thermal-EMF DPDT switch or a low-thermal-EMF
relay to reverse the connections on the DMM, so you can take the reading
forward and reversed, then split the difference. There is the
possibility to introduce thermal-EMF errors from the switch/relay as
well, so I'm wondering if this is a good idea. This sort of makes sense
to me, but I'm not a metrologist, so I would like to hear what others in
this group think about this.
So, just what is the proper way to accomplish this task?
BTW-- I have an Agilent 34420A and an HP 3458A, which would be the
better instrument for this task?
Best Regards,
Ken Peek
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for those interested, and for simplicity, wanted to add this from David which was in voltnuts in 2012.
From: Charles P. Steinmetz <charles_steinmetz at lavabit.com>
To: Discussion of precise voltage measurement <volt-nuts at febo.com>
Sent: Saturday, 15 December 2012, 10:28
Subject: Re: [volt-nuts] Fluke 335A versus HP 740B
David wrote:
I have a Keithley 155 Null Detector how does that rate?
The three usual suspects are the Fluke 845AB, the HP 419A, and Keithley 155. I have one of each, and they are all good meters. The received wisdom is that the Fluke is the one to have. However, in my view, the Keithley is the best of the bunch. It is a bonus if you find one with the rare 1554 AC power module (the 1554 mounts to the rear panel and allows AC operation -- otherwise, it is battery-only).
The main problem today with the HP is that it uses impossible-to-find batteries. Not only are the original batteries unobtainable, I have yet to find a satisfactory replacement strategy. It also does not have a +/- 1 uV range, although I do not count that as a major fault since thermocouple noise in the measurement setup frequently prevents taking full advantage of the 1 uV range.
The Fluke's batteries (sub-C NiCd cells) are readily replaced (though not inexpensively, if you get the best cells). Keithley used four, # 246 9 V carbon cells, which can easily be replaced with common 9 V alkalines or 9 V primary lithium cells that simply plug into the existing connectors.
The HP and Fluke both use photocell choppers. Fluke published pre-release information indicating that they had designed a FET chopper for later production, but I have never seen an 845 with a FET chopper or a schematic of the FET chopper. (Does anyone here have either?) The Keithley was designed with a MOSFET chopper from the start.
Not only is the Keithley the most modern design and the most likely to remain reliable, it also performs the best in my lab. I have had fewer ground loop and shielding problems with it than with the Fluke, and it has less noise and less drift. It is not enough better that most people should sell their Fluke to get a Keithley just for the performance difference (reliability may be another story), but -- IME -- it does perform better.
They are all good meters, but IMO the Keithley is the best of the three. If I had only one, that is the one I'd want.
Best regards,
Charles
Gesendet: Mittwoch, 11. Februar 2015 um 08:55 Uhr
Von: wb6bnq wb6bnq@cox.net
An: "Discussion of precise voltage measurement" volt-nuts@febo.com
Betreff: Re: [volt-nuts] Calibration of voltage standards
To amplify Chuck's point,
The only meter worth considering, if you are going to get one, is the
FLUKE 845. Preferably, the battery operated version which has a higher
isolation leakage resistance. However, the 110
volt rack mount model would do just as equally.
Bill....WB6BNQ
Chuck Harris wrote:
To do a comparison of the sort you are asking about, the
sensitivity of the null meter is much more important than
its ultimate accuracy.
So, neither of your meters is really the right meter to
use for this task. What you want is called a null meter,
and is generally sensitive to the microvolt region.
-Chuck Harris
Ken Peek wrote:
Hi Group,
I have heard of a few different ways to measure one 10V voltage standard
against another 10V voltage standard.
Assume we have two 10V voltage standards. One is calibrated, the other
not only needs to be calibrated, but probably adjusted. For the sake of
simplicity, let's say the two standards are Fluke 732B's.
I think the best way is to connect the two units' (-) terminals
together, then connect a calibrated meter in between the (+) terminals,
and measure the difference. I have also heard that to remove thermal
EMFs, you should use a low-thermal-EMF DPDT switch or a low-thermal-EMF
relay to reverse the connections on the DMM, so you can take the reading
forward and reversed, then split the difference. There is the
possibility to introduce thermal-EMF errors from the switch/relay as
well, so I'm wondering if this is a good idea. This sort of makes sense
to me, but I'm not a metrologist, so I would like to hear what others in
this group think about this.
So, just what is the proper way to accomplish this task?
BTW-- I have an Agilent 34420A and an HP 3458A, which would be the
better instrument for this task?
Best Regards,
Ken Peek
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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To unsubscribe, go to
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and follow the instructions there.
I think I was the Keithley 155 owner that ask the question. Since then I
have added an HP3245A to my equipment which I have set to 1.000000 V DC,
read by my "in calibration" HP3458A, and then compared by the Keithley 155
against my Fluke 732A's 1.000 v output - this is showing a steady -1 uV on
the 155's , 1 or 3uV range. I have replaced the batteries in the 155 with 9
volt (6LF22/MB1604) batteries, works fine. I also have a Fluke 845AB which
I would suggest is less stable. Best regards
Roy Phillips.
-----Original Message-----
From: acbern@gmx.de
Sent: Wednesday, February 11, 2015 10:00 AM
To: volt-nuts@febo.com
Subject: Re: [volt-nuts] Calibration of voltage standards
for those interested, and for simplicity, wanted to add this from David
which was in voltnuts in 2012.
From: Charles P. Steinmetz <charles_steinmetz at lavabit.com>
To: Discussion of precise voltage measurement <volt-nuts at febo.com>
Sent: Saturday, 15 December 2012, 10:28
Subject: Re: [volt-nuts] Fluke 335A versus HP 740B
David wrote:
I have a Keithley 155 Null Detector how does that rate?
The three usual suspects are the Fluke 845AB, the HP 419A, and Keithley 155.
I have one of each, and they are all good meters. The received wisdom is
that the Fluke is the one to have. However, in my view, the Keithley is the
best of the bunch. It is a bonus if you find one with the rare 1554 AC
power module (the 1554 mounts to the rear panel and allows AC operation --
otherwise, it is battery-only).
The main problem today with the HP is that it uses impossible-to-find
batteries. Not only are the original batteries unobtainable, I have yet to
find a satisfactory replacement strategy. It also does not have a +/- 1 uV
range, although I do not count that as a major fault since thermocouple
noise in the measurement setup frequently prevents taking full advantage of
the 1 uV range.
The Fluke's batteries (sub-C NiCd cells) are readily replaced (though not
inexpensively, if you get the best cells). Keithley used four, # 246 9 V
carbon cells, which can easily be replaced with common 9 V alkalines or 9 V
primary lithium cells that simply plug into the existing connectors.
The HP and Fluke both use photocell choppers. Fluke published pre-release
information indicating that they had designed a FET chopper for later
production, but I have never seen an 845 with a FET chopper or a schematic
of the FET chopper. (Does anyone here have either?) The Keithley was
designed with a MOSFET chopper from the start.
Not only is the Keithley the most modern design and the most likely to
remain reliable, it also performs the best in my lab. I have had fewer
ground loop and shielding problems with it than with the Fluke, and it has
less noise and less drift. It is not enough better that most people should
sell their Fluke to get a Keithley just for the performance difference
(reliability may be another story), but -- IME -- it does perform better.
They are all good meters, but IMO the Keithley is the best of the three. If
I had only one, that is the one I'd want.
Best regards,
Charles
Gesendet: Mittwoch, 11. Februar 2015 um 08:55 Uhr
Von: wb6bnq wb6bnq@cox.net
An: "Discussion of precise voltage measurement" volt-nuts@febo.com
Betreff: Re: [volt-nuts] Calibration of voltage standards
To amplify Chuck's point,
The only meter worth considering, if you are going to get one, is the
FLUKE 845. Preferably, the battery operated version which has a higher
isolation leakage resistance. However, the 110
volt rack mount model would do just as equally.
Bill....WB6BNQ
Chuck Harris wrote:
To do a comparison of the sort you are asking about, the
sensitivity of the null meter is much more important than
its ultimate accuracy.
So, neither of your meters is really the right meter to
use for this task. What you want is called a null meter,
and is generally sensitive to the microvolt region.
-Chuck Harris
Ken Peek wrote:
Hi Group,
I have heard of a few different ways to measure one 10V voltage
standard
against another 10V voltage standard.
Assume we have two 10V voltage standards. One is calibrated, the other
not only needs to be calibrated, but probably adjusted. For the sake
of
simplicity, let's say the two standards are Fluke 732B's.
I think the best way is to connect the two units' (-) terminals
together, then connect a calibrated meter in between the (+) terminals,
and measure the difference. I have also heard that to remove thermal
EMFs, you should use a low-thermal-EMF DPDT switch or a low-thermal-EMF
relay to reverse the connections on the DMM, so you can take the
reading
forward and reversed, then split the difference. There is the
possibility to introduce thermal-EMF errors from the switch/relay as
well, so I'm wondering if this is a good idea. This sort of makes
sense
to me, but I'm not a metrologist, so I would like to hear what others
in
this group think about this.
So, just what is the proper way to accomplish this task?
BTW-- I have an Agilent 34420A and an HP 3458A, which would be the
better instrument for this task?
Best Regards,
Ken Peek
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.
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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To unsubscribe, go to
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and follow the instructions there.
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To unsubscribe, go to
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and follow the instructions there.
I have both the Keithley 155 and several Fluke 845AB's.
I too prefer the Keithley 155 over the Fluke and I'm not a big fan of Keithley equipment.
Jeff - KDØORH
----- Original Message -----
From: "R.Phillips" phill.r1@btinternet.com
To: volt-nuts@febo.com
Sent: Wednesday, February 11, 2015 6:00:42 AM
Subject: Re: [volt-nuts] Calibration of voltage standards
I think I was the Keithley 155 owner that ask the question. Since then I
have added an HP3245A to my equipment which I have set to 1.000000 V DC,
read by my "in calibration" HP3458A, and then compared by the Keithley 155
against my Fluke 732A's 1.000 v output - this is showing a steady -1 uV on
the 155's , 1 or 3uV range. I have replaced the batteries in the 155 with 9
volt (6LF22/MB1604) batteries, works fine. I also have a Fluke 845AB which
I would suggest is less stable. Best regards
Roy Phillips.
-----Original Message-----
From: acbern@gmx.de
Sent: Wednesday, February 11, 2015 10:00 AM
To: volt-nuts@febo.com
Subject: Re: [volt-nuts] Calibration of voltage standards
for those interested, and for simplicity, wanted to add this from David
which was in voltnuts in 2012.
From: Charles P. Steinmetz <charles_steinmetz at lavabit.com>
To: Discussion of precise voltage measurement <volt-nuts at febo.com>
Sent: Saturday, 15 December 2012, 10:28
Subject: Re: [volt-nuts] Fluke 335A versus HP 740B
David wrote:
I have a Keithley 155 Null Detector how does that rate?
The three usual suspects are the Fluke 845AB, the HP 419A, and Keithley 155.
I have one of each, and they are all good meters. The received wisdom is
that the Fluke is the one to have. However, in my view, the Keithley is the
best of the bunch. It is a bonus if you find one with the rare 1554 AC
power module (the 1554 mounts to the rear panel and allows AC operation --
otherwise, it is battery-only).
The main problem today with the HP is that it uses impossible-to-find
batteries. Not only are the original batteries unobtainable, I have yet to
find a satisfactory replacement strategy. It also does not have a +/- 1 uV
range, although I do not count that as a major fault since thermocouple
noise in the measurement setup frequently prevents taking full advantage of
the 1 uV range.
The Fluke's batteries (sub-C NiCd cells) are readily replaced (though not
inexpensively, if you get the best cells). Keithley used four, # 246 9 V
carbon cells, which can easily be replaced with common 9 V alkalines or 9 V
primary lithium cells that simply plug into the existing connectors.
The HP and Fluke both use photocell choppers. Fluke published pre-release
information indicating that they had designed a FET chopper for later
production, but I have never seen an 845 with a FET chopper or a schematic
of the FET chopper. (Does anyone here have either?) The Keithley was
designed with a MOSFET chopper from the start.
Not only is the Keithley the most modern design and the most likely to
remain reliable, it also performs the best in my lab. I have had fewer
ground loop and shielding problems with it than with the Fluke, and it has
less noise and less drift. It is not enough better that most people should
sell their Fluke to get a Keithley just for the performance difference
(reliability may be another story), but -- IME -- it does perform better.
They are all good meters, but IMO the Keithley is the best of the three. If
I had only one, that is the one I'd want.
Best regards,
Charles