Empathy List Archives

RE

Randy Evans

Sat, Nov 18, 2017 4:59 AM

I just received an Agilent 3458A that has a problem with noise and a
drifting voltage measurements. I am using two Fluke 732As to compare
absolute voltage measurements over time against the Agilent and an HP
3458A. The HP unit has a new A3 ADC card and seems to be very stable and
low noise, so is being used for comparison. I have been doing simultaneous
absolute voltage measurements and DC Cal Constant measurements several
times a day and then calculating the drift rates of the two units using the
HP Service Note 18 procedure.

The results indicate the Cal Constant drift rate of both units is very
similar and within spec per Service Note 18. However, the absolute value
measurements show the Agilent unit changing 1.1 ppm over a day whereas the
HP unit is within a tenth of a ppm over a day. In my way of thinking the
Cal Constant procedure assumes the voltage reference board in the 3458A is
stable, hence the absolute value reading should remain essentially constant
after each ACAL DCV, which is the case with the HP unit. Since the Agilent
unit shows a steady drift in the absolute reading, this would indicate to
me that the voltage reference board is likely the cause of the problem, and
is also likely the cause of the noisy readings. If so, this is a
“relatively” easy fix (I have several 3458A voltage reference boards, one
of which has been continuously powered up for several years).

The issue is that I have to make a decision to keep or return the Agilent.
It has a cal seal on it and if I open the unit up to change the voltage
reference board, I own it and can’t return it. I would appreciate an
opinion from the members of the group as to what they think the odds are
that the voltage reference board is the source of the problems with the
Agilent 3458A.

Thanks,

Randy Evans

I just received an Agilent 3458A that has a problem with noise and a drifting voltage measurements. I am using two Fluke 732As to compare absolute voltage measurements over time against the Agilent and an HP 3458A. The HP unit has a new A3 ADC card and seems to be very stable and low noise, so is being used for comparison. I have been doing simultaneous absolute voltage measurements and DC Cal Constant measurements several times a day and then calculating the drift rates of the two units using the HP Service Note 18 procedure. The results indicate the Cal Constant drift rate of both units is very similar and within spec per Service Note 18. However, the absolute value measurements show the Agilent unit changing 1.1 ppm over a day whereas the HP unit is within a tenth of a ppm over a day. In my way of thinking the Cal Constant procedure assumes the voltage reference board in the 3458A is stable, hence the absolute value reading should remain essentially constant after each ACAL DCV, which is the case with the HP unit. Since the Agilent unit shows a steady drift in the absolute reading, this would indicate to me that the voltage reference board is likely the cause of the problem, and is also likely the cause of the noisy readings. If so, this is a “relatively” easy fix (I have several 3458A voltage reference boards, one of which has been continuously powered up for several years). The issue is that I have to make a decision to keep or return the Agilent. It has a cal seal on it and if I open the unit up to change the voltage reference board, I own it and can’t return it. I would appreciate an opinion from the members of the group as to what they think the odds are that the voltage reference board is the source of the problems with the Agilent 3458A. Thanks, Randy Evans

IT

Illya Tsemenko

Sat, Nov 18, 2017 12:47 PM

Since you have 732A, testing should be easy enough. Calibrate faulty meter for zero and DCV 10V to 732A, record CAL? 2,1 value. This is your LTZ output. Then leave it running for few days to drift away and calibrate again to same 732A. Check CAL? 2,1 again. Calculate the difference and if it matches output drift (that 1.1ppm/day you mention) - you can be 80% sure that A9 is a problem. Other 19% go to A1 and A3 circuits, as 7V is not used directly in the meter, and there are still gain parts to get +12 and -12VREF on A3 and 10Vish bipolar levels on A1. If your CAL? 2,1 stays same (within 0.3ppm) then A9 is fine.

On November 18, 2017 12:59:53 PM GMT+08:00, Randy Evans randyevans2688@gmail.com wrote:

I just received an Agilent 3458A that has a problem with noise and a
drifting voltage measurements. I am using two Fluke 732As to compare
absolute voltage measurements over time against the Agilent and an HP
3458A. The HP unit has a new A3 ADC card and seems to be very stable
and
low noise, so is being used for comparison. I have been doing
simultaneous
absolute voltage measurements and DC Cal Constant measurements several
times a day and then calculating the drift rates of the two units using
the
HP Service Note 18 procedure.

The results indicate the Cal Constant drift rate of both units is very
similar and within spec per Service Note 18. However, the absolute
value
measurements show the Agilent unit changing 1.1 ppm over a day whereas
the
HP unit is within a tenth of a ppm over a day. In my way of thinking
the
Cal Constant procedure assumes the voltage reference board in the 3458A
is
stable, hence the absolute value reading should remain essentially
constant
after each ACAL DCV, which is the case with the HP unit. Since the
Agilent
unit shows a steady drift in the absolute reading, this would indicate
to
me that the voltage reference board is likely the cause of the problem,
and
is also likely the cause of the noisy readings. If so, this is a
“relatively” easy fix (I have several 3458A voltage reference boards,
one
of which has been continuously powered up for several years).

The issue is that I have to make a decision to keep or return the
Agilent.
It has a cal seal on it and if I open the unit up to change the voltage
reference board, I own it and can’t return it. I would appreciate an
opinion from the members of the group as to what they think the odds
are
that the voltage reference board is the source of the problems with the
Agilent 3458A.

Thanks,

Randy Evans

Since you have 732A, testing should be easy enough. Calibrate faulty meter for zero and DCV 10V to 732A, record CAL? 2,1 value. This is your LTZ output. Then leave it running for few days to drift away and calibrate again to same 732A. Check CAL? 2,1 again. Calculate the difference and if it matches output drift (that 1.1ppm/day you mention) - you can be 80% sure that A9 is a problem. Other 19% go to A1 and A3 circuits, as 7V is not used directly in the meter, and there are still gain parts to get +12 and -12VREF on A3 and 10Vish bipolar levels on A1. If your CAL? 2,1 stays same (within 0.3ppm) then A9 is fine. On November 18, 2017 12:59:53 PM GMT+08:00, Randy Evans <randyevans2688@gmail.com> wrote: >I just received an Agilent 3458A that has a problem with noise and a >drifting voltage measurements. I am using two Fluke 732As to compare >absolute voltage measurements over time against the Agilent and an HP >3458A. The HP unit has a new A3 ADC card and seems to be very stable >and >low noise, so is being used for comparison. I have been doing >simultaneous >absolute voltage measurements and DC Cal Constant measurements several >times a day and then calculating the drift rates of the two units using >the >HP Service Note 18 procedure. > > > >The results indicate the Cal Constant drift rate of both units is very >similar and within spec per Service Note 18. However, the absolute >value >measurements show the Agilent unit changing 1.1 ppm over a day whereas >the >HP unit is within a tenth of a ppm over a day. In my way of thinking >the >Cal Constant procedure assumes the voltage reference board in the 3458A >is >stable, hence the absolute value reading should remain essentially >constant >after each ACAL DCV, which is the case with the HP unit. Since the >Agilent >unit shows a steady drift in the absolute reading, this would indicate >to >me that the voltage reference board is likely the cause of the problem, >and >is also likely the cause of the noisy readings. If so, this is a >“relatively” easy fix (I have several 3458A voltage reference boards, >one >of which has been continuously powered up for several years). > > > >The issue is that I have to make a decision to keep or return the >Agilent. >It has a cal seal on it and if I open the unit up to change the voltage >reference board, I own it and can’t return it. I would appreciate an >opinion from the members of the group as to what they think the odds >are >that the voltage reference board is the source of the problems with the >Agilent 3458A. > > > >Thanks, > > > >Randy Evans

RE

Randy Evans

Sat, Nov 18, 2017 7:17 PM

Illya,

That is a great idea. I will give it a try.

Thanks

On Sat, Nov 18, 2017 at 4:47 AM, Illya Tsemenko illya@xdevs.com wrote:

Since you have 732A, testing should be easy enough. Calibrate faulty meter
for zero and DCV 10V to 732A, record CAL? 2,1 value. This is your LTZ
output. Then leave it running for few days to drift away and calibrate
again to same 732A. Check CAL? 2,1 again. Calculate the difference and if
it matches output drift (that 1.1ppm/day you mention) - you can be 80% sure
that A9 is a problem. Other 19% go to A1 and A3 circuits, as 7V is not used
directly in the meter, and there are still gain parts to get +12 and
-12VREF on A3 and 10Vish bipolar levels on A1. If your CAL? 2,1 stays same
(within 0.3ppm) then A9 is fine.

On November 18, 2017 12:59:53 PM GMT+08:00, Randy Evans <
randyevans2688@gmail.com> wrote:

I just received an Agilent 3458A that has a problem with noise and a
drifting voltage measurements. I am using two Fluke 732As to compare
absolute voltage measurements over time against the Agilent and an HP
3458A. The HP unit has a new A3 ADC card and seems to be very stable and
low noise, so is being used for comparison. I have been doing simultaneous
absolute voltage measurements and DC Cal Constant measurements several
times a day and then calculating the drift rates of the two units using the
HP Service Note 18 procedure.

The results indicate the Cal Constant drift rate of both units is very
similar and within spec per Service Note 18. However, the absolute value
measurements show the Agilent unit changing 1.1 ppm over a day whereas the
HP unit is within a tenth of a ppm over a day. In my way of thinking the
Cal Constant procedure assumes the voltage reference board in the 3458A is
stable, hence the absolute value reading should remain essentially constant
after each ACAL DCV, which is the case with the HP unit. Since the Agilent
unit shows a steady drift in the absolute reading, this would indicate to
me that the voltage reference board is likely the cause of the problem, and
is also likely the cause of the noisy readings. If so, this is a
“relatively” easy fix (I have several 3458A voltage reference boards, one
of which has been continuously powered up for several years).

The issue is that I have to make a decision to keep or return the Agilent.
It has a cal seal on it and if I open the unit up to change the voltage
reference board, I own it and can’t return it. I would appreciate an
opinion from the members of the group as to what they think the odds are
that the voltage reference board is the source of the problems with the
Agilent 3458A.

Thanks,

Randy Evans

Illya, That is a great idea. I will give it a try. Thanks On Sat, Nov 18, 2017 at 4:47 AM, Illya Tsemenko <illya@xdevs.com> wrote: > Since you have 732A, testing should be easy enough. Calibrate faulty meter > for zero and DCV 10V to 732A, record CAL? 2,1 value. This is your LTZ > output. Then leave it running for few days to drift away and calibrate > again to same 732A. Check CAL? 2,1 again. Calculate the difference and if > it matches output drift (that 1.1ppm/day you mention) - you can be 80% sure > that A9 is a problem. Other 19% go to A1 and A3 circuits, as 7V is not used > directly in the meter, and there are still gain parts to get +12 and > -12VREF on A3 and 10Vish bipolar levels on A1. If your CAL? 2,1 stays same > (within 0.3ppm) then A9 is fine. > > > On November 18, 2017 12:59:53 PM GMT+08:00, Randy Evans < > randyevans2688@gmail.com> wrote: >> >> I just received an Agilent 3458A that has a problem with noise and a >> drifting voltage measurements. I am using two Fluke 732As to compare >> absolute voltage measurements over time against the Agilent and an HP >> 3458A. The HP unit has a new A3 ADC card and seems to be very stable and >> low noise, so is being used for comparison. I have been doing simultaneous >> absolute voltage measurements and DC Cal Constant measurements several >> times a day and then calculating the drift rates of the two units using the >> HP Service Note 18 procedure. >> >> >> >> The results indicate the Cal Constant drift rate of both units is very >> similar and within spec per Service Note 18. However, the absolute value >> measurements show the Agilent unit changing 1.1 ppm over a day whereas the >> HP unit is within a tenth of a ppm over a day. In my way of thinking the >> Cal Constant procedure assumes the voltage reference board in the 3458A is >> stable, hence the absolute value reading should remain essentially constant >> after each ACAL DCV, which is the case with the HP unit. Since the Agilent >> unit shows a steady drift in the absolute reading, this would indicate to >> me that the voltage reference board is likely the cause of the problem, and >> is also likely the cause of the noisy readings. If so, this is a >> “relatively” easy fix (I have several 3458A voltage reference boards, one >> of which has been continuously powered up for several years). >> >> >> >> The issue is that I have to make a decision to keep or return the Agilent. >> It has a cal seal on it and if I open the unit up to change the voltage >> reference board, I own it and can’t return it. I would appreciate an >> opinion from the members of the group as to what they think the odds are >> that the voltage reference board is the source of the problems with the >> Agilent 3458A. >> >> >> >> Thanks, >> >> >> >> Randy Evans >> >>

RE

Randy Evans

Sat, Nov 18, 2017 8:58 PM

When I try to execute a 10V cal, I get an error code "209 HARDWARE FAILURE

- INTERNAL OVERLOAD:31" I suspect that the unit has a different security
  code than 3458. I can't change it without opening up the unit, which I
  don't want to do unless I decide to keep it. Do you have any other
  suggestions on how to check the A9 card?

On Sat, Nov 18, 2017 at 11:17 AM, Randy Evans randyevans2688@gmail.com
wrote:

Illya,

That is a great idea. I will give it a try.

Thanks

On Sat, Nov 18, 2017 at 4:47 AM, Illya Tsemenko illya@xdevs.com wrote:

Since you have 732A, testing should be easy enough. Calibrate faulty
meter for zero and DCV 10V to 732A, record CAL? 2,1 value. This is your LTZ
output. Then leave it running for few days to drift away and calibrate
again to same 732A. Check CAL? 2,1 again. Calculate the difference and if
it matches output drift (that 1.1ppm/day you mention) - you can be 80% sure
that A9 is a problem. Other 19% go to A1 and A3 circuits, as 7V is not used
directly in the meter, and there are still gain parts to get +12 and
-12VREF on A3 and 10Vish bipolar levels on A1. If your CAL? 2,1 stays same
(within 0.3ppm) then A9 is fine.

On November 18, 2017 12:59:53 PM GMT+08:00, Randy Evans <
randyevans2688@gmail.com> wrote:

I just received an Agilent 3458A that has a problem with noise and a
drifting voltage measurements. I am using two Fluke 732As to compare
absolute voltage measurements over time against the Agilent and an HP
3458A. The HP unit has a new A3 ADC card and seems to be very stable and
low noise, so is being used for comparison. I have been doing simultaneous
absolute voltage measurements and DC Cal Constant measurements several
times a day and then calculating the drift rates of the two units using the
HP Service Note 18 procedure.

The results indicate the Cal Constant drift rate of both units is very
similar and within spec per Service Note 18. However, the absolute value
measurements show the Agilent unit changing 1.1 ppm over a day whereas the
HP unit is within a tenth of a ppm over a day. In my way of thinking the
Cal Constant procedure assumes the voltage reference board in the 3458A is
stable, hence the absolute value reading should remain essentially constant
after each ACAL DCV, which is the case with the HP unit. Since the Agilent
unit shows a steady drift in the absolute reading, this would indicate to
me that the voltage reference board is likely the cause of the problem, and
is also likely the cause of the noisy readings. If so, this is a
“relatively” easy fix (I have several 3458A voltage reference boards, one
of which has been continuously powered up for several years).

The issue is that I have to make a decision to keep or return the Agilent.
It has a cal seal on it and if I open the unit up to change the voltage
reference board, I own it and can’t return it. I would appreciate an
opinion from the members of the group as to what they think the odds are
that the voltage reference board is the source of the problems with the
Agilent 3458A.

Thanks,

Randy Evans

When I try to execute a 10V cal, I get an error code "209 HARDWARE FAILURE - - INTERNAL OVERLOAD:31" I suspect that the unit has a different security code than 3458. I can't change it without opening up the unit, which I don't want to do unless I decide to keep it. Do you have any other suggestions on how to check the A9 card? On Sat, Nov 18, 2017 at 11:17 AM, Randy Evans <randyevans2688@gmail.com> wrote: > Illya, > > That is a great idea. I will give it a try. > > Thanks > > On Sat, Nov 18, 2017 at 4:47 AM, Illya Tsemenko <illya@xdevs.com> wrote: > >> Since you have 732A, testing should be easy enough. Calibrate faulty >> meter for zero and DCV 10V to 732A, record CAL? 2,1 value. This is your LTZ >> output. Then leave it running for few days to drift away and calibrate >> again to same 732A. Check CAL? 2,1 again. Calculate the difference and if >> it matches output drift (that 1.1ppm/day you mention) - you can be 80% sure >> that A9 is a problem. Other 19% go to A1 and A3 circuits, as 7V is not used >> directly in the meter, and there are still gain parts to get +12 and >> -12VREF on A3 and 10Vish bipolar levels on A1. If your CAL? 2,1 stays same >> (within 0.3ppm) then A9 is fine. >> >> >> On November 18, 2017 12:59:53 PM GMT+08:00, Randy Evans < >> randyevans2688@gmail.com> wrote: >>> >>> I just received an Agilent 3458A that has a problem with noise and a >>> drifting voltage measurements. I am using two Fluke 732As to compare >>> absolute voltage measurements over time against the Agilent and an HP >>> 3458A. The HP unit has a new A3 ADC card and seems to be very stable and >>> low noise, so is being used for comparison. I have been doing simultaneous >>> absolute voltage measurements and DC Cal Constant measurements several >>> times a day and then calculating the drift rates of the two units using the >>> HP Service Note 18 procedure. >>> >>> >>> >>> The results indicate the Cal Constant drift rate of both units is very >>> similar and within spec per Service Note 18. However, the absolute value >>> measurements show the Agilent unit changing 1.1 ppm over a day whereas the >>> HP unit is within a tenth of a ppm over a day. In my way of thinking the >>> Cal Constant procedure assumes the voltage reference board in the 3458A is >>> stable, hence the absolute value reading should remain essentially constant >>> after each ACAL DCV, which is the case with the HP unit. Since the Agilent >>> unit shows a steady drift in the absolute reading, this would indicate to >>> me that the voltage reference board is likely the cause of the problem, and >>> is also likely the cause of the noisy readings. If so, this is a >>> “relatively” easy fix (I have several 3458A voltage reference boards, one >>> of which has been continuously powered up for several years). >>> >>> >>> >>> The issue is that I have to make a decision to keep or return the Agilent. >>> It has a cal seal on it and if I open the unit up to change the voltage >>> reference board, I own it and can’t return it. I would appreciate an >>> opinion from the members of the group as to what they think the odds are >>> that the voltage reference board is the source of the problems with the >>> Agilent 3458A. >>> >>> >>> >>> Thanks, >>> >>> >>> >>> Randy Evans >>> >>> >

TM

Todd Micallef

Sat, Nov 18, 2017 9:10 PM

If you were able to run CAL 0 with the inputs shorted, then security is not
an issue.

After that, try CAL 10.xxxxxx whatever the value is. I think overload means
the expected value is out of range.

On Sat, Nov 18, 2017 at 3:58 PM, Randy Evans randyevans2688@gmail.com
wrote:

When I try to execute a 10V cal, I get an error code "209 HARDWARE FAILURE

- INTERNAL OVERLOAD:31" I suspect that the unit has a different security
  code than 3458. I can't change it without opening up the unit, which I
  don't want to do unless I decide to keep it. Do you have any other
  suggestions on how to check the A9 card?

On Sat, Nov 18, 2017 at 11:17 AM, Randy Evans randyevans2688@gmail.com
wrote:

Illya,

That is a great idea. I will give it a try.

Thanks

On Sat, Nov 18, 2017 at 4:47 AM, Illya Tsemenko illya@xdevs.com wrote:

Since you have 732A, testing should be easy enough. Calibrate faulty
meter for zero and DCV 10V to 732A, record CAL? 2,1 value. This is your

LTZ

output. Then leave it running for few days to drift away and calibrate
again to same 732A. Check CAL? 2,1 again. Calculate the difference and

if

it matches output drift (that 1.1ppm/day you mention) - you can be 80%

sure

that A9 is a problem. Other 19% go to A1 and A3 circuits, as 7V is not

used

directly in the meter, and there are still gain parts to get +12 and
-12VREF on A3 and 10Vish bipolar levels on A1. If your CAL? 2,1 stays

same

(within 0.3ppm) then A9 is fine.

On November 18, 2017 12:59:53 PM GMT+08:00, Randy Evans <
randyevans2688@gmail.com> wrote:

I just received an Agilent 3458A that has a problem with noise and a
drifting voltage measurements. I am using two Fluke 732As to compare
absolute voltage measurements over time against the Agilent and an HP
3458A. The HP unit has a new A3 ADC card and seems to be very stable

and

low noise, so is being used for comparison. I have been doing

simultaneous

absolute voltage measurements and DC Cal Constant measurements several
times a day and then calculating the drift rates of the two units

using the

HP Service Note 18 procedure.

The results indicate the Cal Constant drift rate of both units is very
similar and within spec per Service Note 18. However, the absolute

value

measurements show the Agilent unit changing 1.1 ppm over a day whereas

the

HP unit is within a tenth of a ppm over a day. In my way of thinking

the

Cal Constant procedure assumes the voltage reference board in the

3458A is

stable, hence the absolute value reading should remain essentially

constant

after each ACAL DCV, which is the case with the HP unit. Since the

Agilent

unit shows a steady drift in the absolute reading, this would indicate

to

me that the voltage reference board is likely the cause of the

problem, and

is also likely the cause of the noisy readings. If so, this is a
“relatively” easy fix (I have several 3458A voltage reference boards,

one

of which has been continuously powered up for several years).

The issue is that I have to make a decision to keep or return the

Agilent.

It has a cal seal on it and if I open the unit up to change the voltage
reference board, I own it and can’t return it. I would appreciate an
opinion from the members of the group as to what they think the odds

are

that the voltage reference board is the source of the problems with the
Agilent 3458A.

Thanks,

Randy Evans

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If you were able to run CAL 0 with the inputs shorted, then security is not an issue. After that, try CAL 10.xxxxxx whatever the value is. I think overload means the expected value is out of range. On Sat, Nov 18, 2017 at 3:58 PM, Randy Evans <randyevans2688@gmail.com> wrote: > When I try to execute a 10V cal, I get an error code "209 HARDWARE FAILURE > - - INTERNAL OVERLOAD:31" I suspect that the unit has a different security > code than 3458. I can't change it without opening up the unit, which I > don't want to do unless I decide to keep it. Do you have any other > suggestions on how to check the A9 card? > > On Sat, Nov 18, 2017 at 11:17 AM, Randy Evans <randyevans2688@gmail.com> > wrote: > > > Illya, > > > > That is a great idea. I will give it a try. > > > > Thanks > > > > On Sat, Nov 18, 2017 at 4:47 AM, Illya Tsemenko <illya@xdevs.com> wrote: > > > >> Since you have 732A, testing should be easy enough. Calibrate faulty > >> meter for zero and DCV 10V to 732A, record CAL? 2,1 value. This is your > LTZ > >> output. Then leave it running for few days to drift away and calibrate > >> again to same 732A. Check CAL? 2,1 again. Calculate the difference and > if > >> it matches output drift (that 1.1ppm/day you mention) - you can be 80% > sure > >> that A9 is a problem. Other 19% go to A1 and A3 circuits, as 7V is not > used > >> directly in the meter, and there are still gain parts to get +12 and > >> -12VREF on A3 and 10Vish bipolar levels on A1. If your CAL? 2,1 stays > same > >> (within 0.3ppm) then A9 is fine. > >> > >> > >> On November 18, 2017 12:59:53 PM GMT+08:00, Randy Evans < > >> randyevans2688@gmail.com> wrote: > >>> > >>> I just received an Agilent 3458A that has a problem with noise and a > >>> drifting voltage measurements. I am using two Fluke 732As to compare > >>> absolute voltage measurements over time against the Agilent and an HP > >>> 3458A. The HP unit has a new A3 ADC card and seems to be very stable > and > >>> low noise, so is being used for comparison. I have been doing > simultaneous > >>> absolute voltage measurements and DC Cal Constant measurements several > >>> times a day and then calculating the drift rates of the two units > using the > >>> HP Service Note 18 procedure. > >>> > >>> > >>> > >>> The results indicate the Cal Constant drift rate of both units is very > >>> similar and within spec per Service Note 18. However, the absolute > value > >>> measurements show the Agilent unit changing 1.1 ppm over a day whereas > the > >>> HP unit is within a tenth of a ppm over a day. In my way of thinking > the > >>> Cal Constant procedure assumes the voltage reference board in the > 3458A is > >>> stable, hence the absolute value reading should remain essentially > constant > >>> after each ACAL DCV, which is the case with the HP unit. Since the > Agilent > >>> unit shows a steady drift in the absolute reading, this would indicate > to > >>> me that the voltage reference board is likely the cause of the > problem, and > >>> is also likely the cause of the noisy readings. If so, this is a > >>> “relatively” easy fix (I have several 3458A voltage reference boards, > one > >>> of which has been continuously powered up for several years). > >>> > >>> > >>> > >>> The issue is that I have to make a decision to keep or return the > Agilent. > >>> It has a cal seal on it and if I open the unit up to change the voltage > >>> reference board, I own it and can’t return it. I would appreciate an > >>> opinion from the members of the group as to what they think the odds > are > >>> that the voltage reference board is the source of the problems with the > >>> Agilent 3458A. > >>> > >>> > >>> > >>> Thanks, > >>> > >>> > >>> > >>> Randy Evans > >>> > >>> > > > _______________________________________________ > 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. >

PK

Poul-Henning Kamp

Sat, Nov 18, 2017 9:17 PM

In message CANwu9Jb0yQBdZXei8PoU7F_hDbXvKdgno1J7XfyyAGGYSTX0Og@mail.gmail.com
, Randy Evans writes:

When I try to execute a 10V cal, I get an error code "209 HARDWARE FAILURE

- INTERNAL OVERLOAD:31" I suspect that the unit has a different security
  code than 3458.

The 3458 is quite elonquent, and will say so clearly if that is the
problem.

209 means that the compiled in limit on one of all the many
calibration values is out of range.

--
Poul-Henning Kamp | UNIX since Zilog Zeus 3.20
phk@FreeBSD.ORG | TCP/IP since RFC 956
FreeBSD committer | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.

-------- In message <CANwu9Jb0yQBdZXei8PoU7F_hDbXvKdgno1J7XfyyAGGYSTX0Og@mail.gmail.com> , Randy Evans writes: >When I try to execute a 10V cal, I get an error code "209 HARDWARE FAILURE >- - INTERNAL OVERLOAD:31" I suspect that the unit has a different security >code than 3458. The 3458 is quite elonquent, and will say so clearly if that is the problem. 209 means that the compiled in limit on one of all the many calibration values is out of range. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 phk@FreeBSD.ORG | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence.

RE

Randy Evans

Sat, Nov 18, 2017 10:16 PM

Problem solved! As expected, operator error. When I did the CAL 0, I
shorted the voltage and sense lines separately but did not short them
together. This caused error 209, which caused the CAL 10V to fail since
the zero was not done correctly. All is well now. Still learning.

On Sat, Nov 18, 2017 at 12:58 PM, Randy Evans randyevans2688@gmail.com
wrote:

When I try to execute a 10V cal, I get an error code "209 HARDWARE FAILURE

- INTERNAL OVERLOAD:31" I suspect that the unit has a different
  security code than 3458. I can't change it without opening up the unit,
  which I don't want to do unless I decide to keep it. Do you have any other
  suggestions on how to check the A9 card?

On Sat, Nov 18, 2017 at 11:17 AM, Randy Evans randyevans2688@gmail.com
wrote:

Illya,

That is a great idea. I will give it a try.

Thanks

On Sat, Nov 18, 2017 at 4:47 AM, Illya Tsemenko illya@xdevs.com wrote:

Since you have 732A, testing should be easy enough. Calibrate faulty
meter for zero and DCV 10V to 732A, record CAL? 2,1 value. This is your LTZ
output. Then leave it running for few days to drift away and calibrate
again to same 732A. Check CAL? 2,1 again. Calculate the difference and if
it matches output drift (that 1.1ppm/day you mention) - you can be 80% sure
that A9 is a problem. Other 19% go to A1 and A3 circuits, as 7V is not used
directly in the meter, and there are still gain parts to get +12 and
-12VREF on A3 and 10Vish bipolar levels on A1. If your CAL? 2,1 stays same
(within 0.3ppm) then A9 is fine.

On November 18, 2017 12:59:53 PM GMT+08:00, Randy Evans <
randyevans2688@gmail.com> wrote:

I just received an Agilent 3458A that has a problem with noise and a
drifting voltage measurements. I am using two Fluke 732As to compare
absolute voltage measurements over time against the Agilent and an HP
3458A. The HP unit has a new A3 ADC card and seems to be very stable and
low noise, so is being used for comparison. I have been doing simultaneous
absolute voltage measurements and DC Cal Constant measurements several
times a day and then calculating the drift rates of the two units using the
HP Service Note 18 procedure.

The results indicate the Cal Constant drift rate of both units is very
similar and within spec per Service Note 18. However, the absolute value
measurements show the Agilent unit changing 1.1 ppm over a day whereas the
HP unit is within a tenth of a ppm over a day. In my way of thinking the
Cal Constant procedure assumes the voltage reference board in the 3458A is
stable, hence the absolute value reading should remain essentially constant
after each ACAL DCV, which is the case with the HP unit. Since the Agilent
unit shows a steady drift in the absolute reading, this would indicate to
me that the voltage reference board is likely the cause of the problem, and
is also likely the cause of the noisy readings. If so, this is a
“relatively” easy fix (I have several 3458A voltage reference boards, one
of which has been continuously powered up for several years).

The issue is that I have to make a decision to keep or return the Agilent.
It has a cal seal on it and if I open the unit up to change the voltage
reference board, I own it and can’t return it. I would appreciate an
opinion from the members of the group as to what they think the odds are
that the voltage reference board is the source of the problems with the
Agilent 3458A.

Thanks,

Randy Evans

Problem solved! As expected, operator error. When I did the CAL 0, I shorted the voltage and sense lines separately but did not short them together. This caused error 209, which caused the CAL 10V to fail since the zero was not done correctly. All is well now. Still learning. On Sat, Nov 18, 2017 at 12:58 PM, Randy Evans <randyevans2688@gmail.com> wrote: > When I try to execute a 10V cal, I get an error code "209 HARDWARE FAILURE > - - INTERNAL OVERLOAD:31" I suspect that the unit has a different > security code than 3458. I can't change it without opening up the unit, > which I don't want to do unless I decide to keep it. Do you have any other > suggestions on how to check the A9 card? > > On Sat, Nov 18, 2017 at 11:17 AM, Randy Evans <randyevans2688@gmail.com> > wrote: > >> Illya, >> >> That is a great idea. I will give it a try. >> >> Thanks >> >> On Sat, Nov 18, 2017 at 4:47 AM, Illya Tsemenko <illya@xdevs.com> wrote: >> >>> Since you have 732A, testing should be easy enough. Calibrate faulty >>> meter for zero and DCV 10V to 732A, record CAL? 2,1 value. This is your LTZ >>> output. Then leave it running for few days to drift away and calibrate >>> again to same 732A. Check CAL? 2,1 again. Calculate the difference and if >>> it matches output drift (that 1.1ppm/day you mention) - you can be 80% sure >>> that A9 is a problem. Other 19% go to A1 and A3 circuits, as 7V is not used >>> directly in the meter, and there are still gain parts to get +12 and >>> -12VREF on A3 and 10Vish bipolar levels on A1. If your CAL? 2,1 stays same >>> (within 0.3ppm) then A9 is fine. >>> >>> >>> On November 18, 2017 12:59:53 PM GMT+08:00, Randy Evans < >>> randyevans2688@gmail.com> wrote: >>>> >>>> I just received an Agilent 3458A that has a problem with noise and a >>>> drifting voltage measurements. I am using two Fluke 732As to compare >>>> absolute voltage measurements over time against the Agilent and an HP >>>> 3458A. The HP unit has a new A3 ADC card and seems to be very stable and >>>> low noise, so is being used for comparison. I have been doing simultaneous >>>> absolute voltage measurements and DC Cal Constant measurements several >>>> times a day and then calculating the drift rates of the two units using the >>>> HP Service Note 18 procedure. >>>> >>>> >>>> >>>> The results indicate the Cal Constant drift rate of both units is very >>>> similar and within spec per Service Note 18. However, the absolute value >>>> measurements show the Agilent unit changing 1.1 ppm over a day whereas the >>>> HP unit is within a tenth of a ppm over a day. In my way of thinking the >>>> Cal Constant procedure assumes the voltage reference board in the 3458A is >>>> stable, hence the absolute value reading should remain essentially constant >>>> after each ACAL DCV, which is the case with the HP unit. Since the Agilent >>>> unit shows a steady drift in the absolute reading, this would indicate to >>>> me that the voltage reference board is likely the cause of the problem, and >>>> is also likely the cause of the noisy readings. If so, this is a >>>> “relatively” easy fix (I have several 3458A voltage reference boards, one >>>> of which has been continuously powered up for several years). >>>> >>>> >>>> >>>> The issue is that I have to make a decision to keep or return the Agilent. >>>> It has a cal seal on it and if I open the unit up to change the voltage >>>> reference board, I own it and can’t return it. I would appreciate an >>>> opinion from the members of the group as to what they think the odds are >>>> that the voltage reference board is the source of the problems with the >>>> Agilent 3458A. >>>> >>>> >>>> >>>> Thanks, >>>> >>>> >>>> >>>> Randy Evans >>>> >>>> >> >

RE

Randy Evans

Fri, Nov 24, 2017 12:40 AM

Illya,

I ran the test you suggested over 4 days and got 7.19114068 VDC on the
start of the test and 7.19113736 VDC at the end of the fourth day (96 hours
later). I calculate a total of 0.46 ppm drift, which seems excessive but
does not account for the 1.1 ppm/day I measured overall. I suspect the A3
card is the primary source of drifting. Since the unit is a late model
Agilent unit, that is well beyond the expected range of units described in
Service Note 18. What do you think?

Thanks,

Randy Evans

On Sat, Nov 18, 2017 at 4:47 AM, Illya Tsemenko illya@xdevs.com wrote:

Since you have 732A, testing should be easy enough. Calibrate faulty meter
for zero and DCV 10V to 732A, record CAL? 2,1 value. This is your LTZ
output. Then leave it running for few days to drift away and calibrate
again to same 732A. Check CAL? 2,1 again. Calculate the difference and if
it matches output drift (that 1.1ppm/day you mention) - you can be 80% sure
that A9 is a problem. Other 19% go to A1 and A3 circuits, as 7V is not used
directly in the meter, and there are still gain parts to get +12 and
-12VREF on A3 and 10Vish bipolar levels on A1. If your CAL? 2,1 stays same
(within 0.3ppm) then A9 is fine.

On November 18, 2017 12:59:53 PM GMT+08:00, Randy Evans <
randyevans2688@gmail.com> wrote:

I just received an Agilent 3458A that has a problem with noise and a
drifting voltage measurements. I am using two Fluke 732As to compare
absolute voltage measurements over time against the Agilent and an HP
3458A. The HP unit has a new A3 ADC card and seems to be very stable and
low noise, so is being used for comparison. I have been doing simultaneous
absolute voltage measurements and DC Cal Constant measurements several
times a day and then calculating the drift rates of the two units using the
HP Service Note 18 procedure.

The results indicate the Cal Constant drift rate of both units is very
similar and within spec per Service Note 18. However, the absolute value
measurements show the Agilent unit changing 1.1 ppm over a day whereas the
HP unit is within a tenth of a ppm over a day. In my way of thinking the
Cal Constant procedure assumes the voltage reference board in the 3458A is
stable, hence the absolute value reading should remain essentially constant
after each ACAL DCV, which is the case with the HP unit. Since the Agilent
unit shows a steady drift in the absolute reading, this would indicate to
me that the voltage reference board is likely the cause of the problem, and
is also likely the cause of the noisy readings. If so, this is a
“relatively” easy fix (I have several 3458A voltage reference boards, one
of which has been continuously powered up for several years).

The issue is that I have to make a decision to keep or return the Agilent.
It has a cal seal on it and if I open the unit up to change the voltage
reference board, I own it and can’t return it. I would appreciate an
opinion from the members of the group as to what they think the odds are
that the voltage reference board is the source of the problems with the
Agilent 3458A.

Thanks,

Randy Evans

Illya, I ran the test you suggested over 4 days and got 7.19114068 VDC on the start of the test and 7.19113736 VDC at the end of the fourth day (96 hours later). I calculate a total of 0.46 ppm drift, which seems excessive but does not account for the 1.1 ppm/day I measured overall. I suspect the A3 card is the primary source of drifting. Since the unit is a late model Agilent unit, that is well beyond the expected range of units described in Service Note 18. What do you think? Thanks, Randy Evans On Sat, Nov 18, 2017 at 4:47 AM, Illya Tsemenko <illya@xdevs.com> wrote: > Since you have 732A, testing should be easy enough. Calibrate faulty meter > for zero and DCV 10V to 732A, record CAL? 2,1 value. This is your LTZ > output. Then leave it running for few days to drift away and calibrate > again to same 732A. Check CAL? 2,1 again. Calculate the difference and if > it matches output drift (that 1.1ppm/day you mention) - you can be 80% sure > that A9 is a problem. Other 19% go to A1 and A3 circuits, as 7V is not used > directly in the meter, and there are still gain parts to get +12 and > -12VREF on A3 and 10Vish bipolar levels on A1. If your CAL? 2,1 stays same > (within 0.3ppm) then A9 is fine. > > > On November 18, 2017 12:59:53 PM GMT+08:00, Randy Evans < > randyevans2688@gmail.com> wrote: >> >> I just received an Agilent 3458A that has a problem with noise and a >> drifting voltage measurements. I am using two Fluke 732As to compare >> absolute voltage measurements over time against the Agilent and an HP >> 3458A. The HP unit has a new A3 ADC card and seems to be very stable and >> low noise, so is being used for comparison. I have been doing simultaneous >> absolute voltage measurements and DC Cal Constant measurements several >> times a day and then calculating the drift rates of the two units using the >> HP Service Note 18 procedure. >> >> >> >> The results indicate the Cal Constant drift rate of both units is very >> similar and within spec per Service Note 18. However, the absolute value >> measurements show the Agilent unit changing 1.1 ppm over a day whereas the >> HP unit is within a tenth of a ppm over a day. In my way of thinking the >> Cal Constant procedure assumes the voltage reference board in the 3458A is >> stable, hence the absolute value reading should remain essentially constant >> after each ACAL DCV, which is the case with the HP unit. Since the Agilent >> unit shows a steady drift in the absolute reading, this would indicate to >> me that the voltage reference board is likely the cause of the problem, and >> is also likely the cause of the noisy readings. If so, this is a >> “relatively” easy fix (I have several 3458A voltage reference boards, one >> of which has been continuously powered up for several years). >> >> >> >> The issue is that I have to make a decision to keep or return the Agilent. >> It has a cal seal on it and if I open the unit up to change the voltage >> reference board, I own it and can’t return it. I would appreciate an >> opinion from the members of the group as to what they think the odds are >> that the voltage reference board is the source of the problems with the >> Agilent 3458A. >> >> >> >> Thanks, >> >> >> >> Randy Evans >> >>

IT

Illya Tsemenko

Fri, Nov 24, 2017 1:18 AM

Well, one thing you can know for sure , that reference is indeed broken. Drift over a day should be way below the noise floor (<0.1ppm). With 1.7x gain of ADC scale that drift rate gives you around 0.8ppm +/- 0.3ppm due to zener noise. So it is in line of 1.1ppm/day. If ACAL DCV does not remove drift then A3 is probably fine.

Since reference is much easier to troubleshoot and fix I would go with replacing LTZ chip and testing if drift go away, if that have any help on your desire to keep meter.

Also serial number range in SN doesn't mean much for you, as meter history is unknown and it still may have been serviced at some time.

On November 24, 2017 8:40:00 AM GMT+08:00, Randy Evans randyevans2688@gmail.com wrote:

Illya,

I ran the test you suggested over 4 days and got 7.19114068 VDC on the
start of the test and 7.19113736 VDC at the end of the fourth day (96
hours
later). I calculate a total of 0.46 ppm drift, which seems excessive
but
does not account for the 1.1 ppm/day I measured overall. I suspect the
A3
card is the primary source of drifting. Since the unit is a late model
Agilent unit, that is well beyond the expected range of units described
in
Service Note 18. What do you think?

Thanks,

Randy Evans

On Sat, Nov 18, 2017 at 4:47 AM, Illya Tsemenko illya@xdevs.com
wrote:

Since you have 732A, testing should be easy enough. Calibrate faulty

meter

for zero and DCV 10V to 732A, record CAL? 2,1 value. This is your LTZ
output. Then leave it running for few days to drift away and

calibrate

again to same 732A. Check CAL? 2,1 again. Calculate the difference

and if

it matches output drift (that 1.1ppm/day you mention) - you can be

80% sure

that A9 is a problem. Other 19% go to A1 and A3 circuits, as 7V is

not used

directly in the meter, and there are still gain parts to get +12 and
-12VREF on A3 and 10Vish bipolar levels on A1. If your CAL? 2,1 stays

same

(within 0.3ppm) then A9 is fine.

On November 18, 2017 12:59:53 PM GMT+08:00, Randy Evans <
randyevans2688@gmail.com> wrote:

I just received an Agilent 3458A that has a problem with noise and a
drifting voltage measurements. I am using two Fluke 732As to

compare

absolute voltage measurements over time against the Agilent and an

HP

3458A. The HP unit has a new A3 ADC card and seems to be very

stable and

low noise, so is being used for comparison. I have been doing

simultaneous

absolute voltage measurements and DC Cal Constant measurements

several

times a day and then calculating the drift rates of the two units

using the

HP Service Note 18 procedure.

The results indicate the Cal Constant drift rate of both units is

very

similar and within spec per Service Note 18. However, the absolute

value

measurements show the Agilent unit changing 1.1 ppm over a day

whereas the

HP unit is within a tenth of a ppm over a day. In my way of

thinking the

Cal Constant procedure assumes the voltage reference board in the

3458A is

stable, hence the absolute value reading should remain essentially

constant

after each ACAL DCV, which is the case with the HP unit. Since the

Agilent

unit shows a steady drift in the absolute reading, this would

indicate to

me that the voltage reference board is likely the cause of the

problem, and

is also likely the cause of the noisy readings. If so, this is a
“relatively” easy fix (I have several 3458A voltage reference

boards, one

of which has been continuously powered up for several years).

The issue is that I have to make a decision to keep or return the

Agilent.

It has a cal seal on it and if I open the unit up to change the

voltage

reference board, I own it and can’t return it. I would appreciate

an

opinion from the members of the group as to what they think the odds

are

that the voltage reference board is the source of the problems with

the

Agilent 3458A.

Thanks,

Randy Evans

Well, one thing you can know for sure , that reference is indeed broken. Drift over a day should be way below the noise floor (<0.1ppm). With 1.7x gain of ADC scale that drift rate gives you around 0.8ppm +/- 0.3ppm due to zener noise. So it is in line of 1.1ppm/day. If ACAL DCV does not remove drift then A3 is probably fine. Since reference is much easier to troubleshoot and fix I would go with replacing LTZ chip and testing if drift go away, if that have any help on your desire to keep meter. Also serial number range in SN doesn't mean much for you, as meter history is unknown and it still may have been serviced at some time. On November 24, 2017 8:40:00 AM GMT+08:00, Randy Evans <randyevans2688@gmail.com> wrote: >Illya, > >I ran the test you suggested over 4 days and got 7.19114068 VDC on the >start of the test and 7.19113736 VDC at the end of the fourth day (96 >hours >later). I calculate a total of 0.46 ppm drift, which seems excessive >but >does not account for the 1.1 ppm/day I measured overall. I suspect the >A3 >card is the primary source of drifting. Since the unit is a late model >Agilent unit, that is well beyond the expected range of units described >in >Service Note 18. What do you think? > >Thanks, > >Randy Evans > >On Sat, Nov 18, 2017 at 4:47 AM, Illya Tsemenko <illya@xdevs.com> >wrote: > >> Since you have 732A, testing should be easy enough. Calibrate faulty >meter >> for zero and DCV 10V to 732A, record CAL? 2,1 value. This is your LTZ >> output. Then leave it running for few days to drift away and >calibrate >> again to same 732A. Check CAL? 2,1 again. Calculate the difference >and if >> it matches output drift (that 1.1ppm/day you mention) - you can be >80% sure >> that A9 is a problem. Other 19% go to A1 and A3 circuits, as 7V is >not used >> directly in the meter, and there are still gain parts to get +12 and >> -12VREF on A3 and 10Vish bipolar levels on A1. If your CAL? 2,1 stays >same >> (within 0.3ppm) then A9 is fine. >> >> >> On November 18, 2017 12:59:53 PM GMT+08:00, Randy Evans < >> randyevans2688@gmail.com> wrote: >>> >>> I just received an Agilent 3458A that has a problem with noise and a >>> drifting voltage measurements. I am using two Fluke 732As to >compare >>> absolute voltage measurements over time against the Agilent and an >HP >>> 3458A. The HP unit has a new A3 ADC card and seems to be very >stable and >>> low noise, so is being used for comparison. I have been doing >simultaneous >>> absolute voltage measurements and DC Cal Constant measurements >several >>> times a day and then calculating the drift rates of the two units >using the >>> HP Service Note 18 procedure. >>> >>> >>> >>> The results indicate the Cal Constant drift rate of both units is >very >>> similar and within spec per Service Note 18. However, the absolute >value >>> measurements show the Agilent unit changing 1.1 ppm over a day >whereas the >>> HP unit is within a tenth of a ppm over a day. In my way of >thinking the >>> Cal Constant procedure assumes the voltage reference board in the >3458A is >>> stable, hence the absolute value reading should remain essentially >constant >>> after each ACAL DCV, which is the case with the HP unit. Since the >Agilent >>> unit shows a steady drift in the absolute reading, this would >indicate to >>> me that the voltage reference board is likely the cause of the >problem, and >>> is also likely the cause of the noisy readings. If so, this is a >>> “relatively” easy fix (I have several 3458A voltage reference >boards, one >>> of which has been continuously powered up for several years). >>> >>> >>> >>> The issue is that I have to make a decision to keep or return the >Agilent. >>> It has a cal seal on it and if I open the unit up to change the >voltage >>> reference board, I own it and can’t return it. I would appreciate >an >>> opinion from the members of the group as to what they think the odds >are >>> that the voltage reference board is the source of the problems with >the >>> Agilent 3458A. >>> >>> >>> >>> Thanks, >>> >>> >>> >>> Randy Evans >>> >>>

RE

Randy Evans

Fri, Nov 24, 2017 1:32 AM

Illya,

Can you explain why you say " If ACAL DCV does not remove drift then A3 is
probably fine". I don't really follow the argument.

Randy

On Thu, Nov 23, 2017 at 5:18 PM, Illya Tsemenko illya@xdevs.com wrote:

Well, one thing you can know for sure , that reference is indeed broken.
Drift over a day should be way below the noise floor (<0.1ppm). With 1.7x
gain of ADC scale that drift rate gives you around 0.8ppm +/- 0.3ppm due to
zener noise. So it is in line of 1.1ppm/day. If ACAL DCV does not remove
drift then A3 is probably fine.

Since reference is much easier to troubleshoot and fix I would go with
replacing LTZ chip and testing if drift go away, if that have any help on
your desire to keep meter.

Also serial number range in SN doesn't mean much for you, as meter history
is unknown and it still may have been serviced at some time.

On November 24, 2017 8:40:00 AM GMT+08:00, Randy Evans <
randyevans2688@gmail.com> wrote:

Illya,

I ran the test you suggested over 4 days and got 7.19114068 VDC on the
start of the test and 7.19113736 VDC at the end of the fourth day (96 hours
later). I calculate a total of 0.46 ppm drift, which seems excessive but
does not account for the 1.1 ppm/day I measured overall. I suspect the A3
card is the primary source of drifting. Since the unit is a late model
Agilent unit, that is well beyond the expected range of units described in
Service Note 18. What do you think?

Thanks,

Randy Evans

On Sat, Nov 18, 2017 at 4:47 AM, Illya Tsemenko illya@xdevs.com wrote:

Since you have 732A, testing should be easy enough. Calibrate faulty
meter for zero and DCV 10V to 732A, record CAL? 2,1 value. This is your LTZ
output. Then leave it running for few days to drift away and calibrate
again to same 732A. Check CAL? 2,1 again. Calculate the difference and if
it matches output drift (that 1.1ppm/day you mention) - you can be 80% sure
that A9 is a problem. Other 19% go to A1 and A3 circuits, as 7V is not used
directly in the meter, and there are still gain parts to get +12 and
-12VREF on A3 and 10Vish bipolar levels on A1. If your CAL? 2,1 stays same
(within 0.3ppm) then A9 is fine.

On November 18, 2017 12:59:53 PM GMT+08:00, Randy Evans <
randyevans2688@gmail.com> wrote:

I just received an Agilent 3458A that has a problem with noise and a
drifting voltage measurements. I am using two Fluke 732As to compare
absolute voltage measurements over time against the Agilent and an HP
3458A. The HP unit has a new A3 ADC card and seems to be very stable and
low noise, so is being used for comparison. I have been doing simultaneous
absolute voltage measurements and DC Cal Constant measurements several
times a day and then calculating the drift rates of the two units using the
HP Service Note 18 procedure.

The results indicate the Cal Constant drift rate of both units is very
similar and within spec per Service Note 18. However, the absolute value
measurements show the Agilent unit changing 1.1 ppm over a day whereas the
HP unit is within a tenth of a ppm over a day. In my way of thinking the
Cal Constant procedure assumes the voltage reference board in the 3458A is
stable, hence the absolute value reading should remain essentially constant
after each ACAL DCV, which is the case with the HP unit. Since the Agilent
unit shows a steady drift in the absolute reading, this would indicate to
me that the voltage reference board is likely the cause of the problem, and
is also likely the cause of the noisy readings. If so, this is a
“relatively” easy fix (I have several 3458A voltage reference boards, one
of which has been continuously powered up for several years).

The issue is that I have to make a decision to keep or return the Agilent.
It has a cal seal on it and if I open the unit up to change the voltage
reference board, I own it and can’t return it. I would appreciate an
opinion from the members of the group as to what they think the odds are
that the voltage reference board is the source of the problems with the
Agilent 3458A.

Thanks,

Randy Evans

Illya, Can you explain why you say " If ACAL DCV does not remove drift then A3 is probably fine". I don't really follow the argument. Randy On Thu, Nov 23, 2017 at 5:18 PM, Illya Tsemenko <illya@xdevs.com> wrote: > Well, one thing you can know for sure , that reference is indeed broken. > Drift over a day should be way below the noise floor (<0.1ppm). With 1.7x > gain of ADC scale that drift rate gives you around 0.8ppm +/- 0.3ppm due to > zener noise. So it is in line of 1.1ppm/day. If ACAL DCV does not remove > drift then A3 is probably fine. > > Since reference is much easier to troubleshoot and fix I would go with > replacing LTZ chip and testing if drift go away, if that have any help on > your desire to keep meter. > > Also serial number range in SN doesn't mean much for you, as meter history > is unknown and it still may have been serviced at some time. > > On November 24, 2017 8:40:00 AM GMT+08:00, Randy Evans < > randyevans2688@gmail.com> wrote: >> >> Illya, >> >> I ran the test you suggested over 4 days and got 7.19114068 VDC on the >> start of the test and 7.19113736 VDC at the end of the fourth day (96 hours >> later). I calculate a total of 0.46 ppm drift, which seems excessive but >> does not account for the 1.1 ppm/day I measured overall. I suspect the A3 >> card is the primary source of drifting. Since the unit is a late model >> Agilent unit, that is well beyond the expected range of units described in >> Service Note 18. What do you think? >> >> Thanks, >> >> Randy Evans >> >> On Sat, Nov 18, 2017 at 4:47 AM, Illya Tsemenko <illya@xdevs.com> wrote: >> >>> Since you have 732A, testing should be easy enough. Calibrate faulty >>> meter for zero and DCV 10V to 732A, record CAL? 2,1 value. This is your LTZ >>> output. Then leave it running for few days to drift away and calibrate >>> again to same 732A. Check CAL? 2,1 again. Calculate the difference and if >>> it matches output drift (that 1.1ppm/day you mention) - you can be 80% sure >>> that A9 is a problem. Other 19% go to A1 and A3 circuits, as 7V is not used >>> directly in the meter, and there are still gain parts to get +12 and >>> -12VREF on A3 and 10Vish bipolar levels on A1. If your CAL? 2,1 stays same >>> (within 0.3ppm) then A9 is fine. >>> >>> >>> On November 18, 2017 12:59:53 PM GMT+08:00, Randy Evans < >>> randyevans2688@gmail.com> wrote: >>>> >>>> I just received an Agilent 3458A that has a problem with noise and a >>>> drifting voltage measurements. I am using two Fluke 732As to compare >>>> absolute voltage measurements over time against the Agilent and an HP >>>> 3458A. The HP unit has a new A3 ADC card and seems to be very stable and >>>> low noise, so is being used for comparison. I have been doing simultaneous >>>> absolute voltage measurements and DC Cal Constant measurements several >>>> times a day and then calculating the drift rates of the two units using the >>>> HP Service Note 18 procedure. >>>> >>>> >>>> >>>> The results indicate the Cal Constant drift rate of both units is very >>>> similar and within spec per Service Note 18. However, the absolute value >>>> measurements show the Agilent unit changing 1.1 ppm over a day whereas the >>>> HP unit is within a tenth of a ppm over a day. In my way of thinking the >>>> Cal Constant procedure assumes the voltage reference board in the 3458A is >>>> stable, hence the absolute value reading should remain essentially constant >>>> after each ACAL DCV, which is the case with the HP unit. Since the Agilent >>>> unit shows a steady drift in the absolute reading, this would indicate to >>>> me that the voltage reference board is likely the cause of the problem, and >>>> is also likely the cause of the noisy readings. If so, this is a >>>> “relatively” easy fix (I have several 3458A voltage reference boards, one >>>> of which has been continuously powered up for several years). >>>> >>>> >>>> >>>> The issue is that I have to make a decision to keep or return the Agilent. >>>> It has a cal seal on it and if I open the unit up to change the voltage >>>> reference board, I own it and can’t return it. I would appreciate an >>>> opinion from the members of the group as to what they think the odds are >>>> that the voltage reference board is the source of the problems with the >>>> Agilent 3458A. >>>> >>>> >>>> >>>> Thanks, >>>> >>>> >>>> >>>> Randy Evans >>>> >>>> >>

volt-nuts@lists.febo.com

Agilent 3458A Issues