Low level AC measuremets with HP 34401...

[Reinhard Zwirner]

Hello,

Due to the used RMS converter low level AC measurememts with this DMM
are less precise to incorrect. There is a lab note as to this problem
by Gellerlabs containing three pictures. I have this note which,
unfortunately, lacks the mentioned pictures. And, unfortunately too,
the link to this note

<http://www.gellerlabs.com/34401A%20AC%20zero.htm>

doesn\'t work any more. Has anyone of you those pictures and could
provide them? Many thanks in advance.

Regards

Reinhard

 

[Lasse Langwadt Christensen]

torsdag den 23. december 2021 kl. 02.54.33 UTC+1 skrev Reinhard Zwirner:

Hello,

Due to the used RMS converter low level AC measurememts with this DMM
are less precise to incorrect. There is a lab note as to this problem
by Gellerlabs containing three pictures. I have this note which,
unfortunately, lacks the mentioned pictures. And, unfortunately too,
the link to this note

http://www.gellerlabs.com/34401A%20AC%20zero.htm

doesn\'t work any more. Has anyone of you those pictures and could
provide them? Many thanks in advance.

Regards

Reinhard

google says, .. https://pearl-hifi.com/06_Lit_Archive/15_Mfrs_Publications/20_HP_Agilent/01_HP_3400B_20MHZ_True_RMS_Voltmeter/Geller%20Labs/34401A%20AC%20zero.pdf

 

[server]

On Thu, 23 Dec 2021 02:54:27 +0100, Reinhard Zwirner
<reinhard.zwirner@t-online.de> wrote:

Hello,

Due to the used RMS converter low level AC measurememts with this DMM
are less precise to incorrect. There is a lab note as to this problem
by Gellerlabs containing three pictures. I have this note which,
unfortunately, lacks the mentioned pictures. And, unfortunately too,
the link to this note

http://www.gellerlabs.com/34401A%20AC%20zero.htm

doesn\'t work any more. Has anyone of you those pictures and could
provide them? Many thanks in advance.

Regards

Reinhard

That DVM has a huge amount of noise kicked into the front end from the
VF display. They hid that by zeroing AC measurements much below 1 mV.

I like the Fluke better.



--

I yam what I yam - Popeye

 

[Phil Allison]

Reinhard Zwirner wrote:
==================

Due to the used RMS converter low level AC measurememts with this DMM
are less precise to incorrect.

** Amplify your signal prior to the DMM.
By 10x or 100X using say a wide band op-amp.

I use a 1000X pre amp for low level noise measurements.


...... Phil

 

[Don]

Lasse Langwadt Christensen wrote:

skrev Reinhard Zwirner:
Hello,

Due to the used RMS converter low level AC measurememts with this DMM
are less precise to incorrect. There is a lab note as to this problem
by Gellerlabs containing three pictures. I have this note which,
unfortunately, lacks the mentioned pictures. And, unfortunately too,
the link to this note

http://www.gellerlabs.com/34401A%20AC%20zero.htm

doesn\'t work any more. Has anyone of you those pictures and could
provide them? Many thanks in advance.

Regards

Reinhard


google says, .. https://pearl-hifi.com/06_Lit_Archive/15_Mfrs_Publications/20_HP_Agilent/01_HP_3400B_20MHZ_True_RMS_Voltmeter/Geller%20Labs/34401A%20AC%20zero.pdf

It\'s also available in HTML format at:

http://web.archive.org/web/20090322154522/http://www.gellerlabs.com/34401A%20AC%20zero.htm

Danke,

--
Don, KB7RPU, https://www.qsl.net/kb7rpu
There was a young lady named Bright Whose speed was far faster than light;
She set out one day In a relative way And returned on the previous night.

 

[Don Y]

On 12/22/2021 6:54 PM, Reinhard Zwirner wrote:

Hello,

Due to the used RMS converter low level AC measurememts with this DMM
are less precise to incorrect. There is a lab note as to this problem
by Gellerlabs containing three pictures. I have this note which,
unfortunately, lacks the mentioned pictures. And, unfortunately too,
the link to this note

http://www.gellerlabs.com/34401A%20AC%20zero.htm

doesn\'t work any more. Has anyone of you those pictures and could
provide them? Many thanks in advance.

Try:

<https://web.archive.org/web/20090106175105/http://www.gellerlabs.com/34401A%20AC%20zero.htm>

 

[Phil Allison]

Phil Allison wrote:
==============

Reinhard Zwirner wrote:
==================

Due to the used RMS converter low level AC measurememts with this DMM
are less precise to incorrect.

** Amplify your signal prior to the DMM.
By 10x or 100X using say a wide band op-amp.

I use a 1000X pre amp for low level noise measurements.

** FYI:

I have a 4.5. digit ( 20,000 count ) DMM that employs an AD536 rms-DC converter - cousin of the AD637 in the HP.
The converter IC has bandwidth inversely proportional to the input voltage, so 10% of range is a good place to stop thinking it very accurate.
Using one with a 4.5 digit meter is pushing it, so 6.5 is off the map.

Suspect the HP already has 10X and maybe 100X gain stages internally, prior to the converter.
In any case, an external pre-amp is the go.


...... Phil

 

[Klaus Kragelund]

23.12.21 03:03, jlarkin@highlandsniptechnology.com wrote:

On Thu, 23 Dec 2021 02:54:27 +0100, Reinhard Zwirner
reinhard.zwirner@t-online.de> wrote:

Hello,

Due to the used RMS converter low level AC measurememts with this DMM
are less precise to incorrect. There is a lab note as to this problem
by Gellerlabs containing three pictures. I have this note which,
unfortunately, lacks the mentioned pictures. And, unfortunately too,
the link to this note

http://www.gellerlabs.com/34401A%20AC%20zero.htm

doesn\'t work any more. Has anyone of you those pictures and could
provide them? Many thanks in advance.

Regards

Reinhard

That DVM has a huge amount of noise kicked into the front end from the
VF display. They hid that by zeroing AC measurements much below 1 mV.

I like the Fluke better.

The 34401A was my first bench DMM. Bought it in 1998.

I have never calibrated it, could not afford it

This year I went the consultant route, so bought 3 Siglent DMMs. Just for fun, I connected the same references voltage to the 3 Siglent and the 34401A
They measured the same except for minor last digit difference

Not willing to spend on calibrations, the next best thing is to compare to other instruments. Quite unlikely that they would drift in the same direction ?

By the way, I paid a lot for the 34401A, now I can get 4 Siglents for the same price


--
Klaus

 

[Cydrome Leader]

Klaus Kragelund <klauskvik@hotmail.com> wrote:

23.12.21 03:03, jlarkin@highlandsniptechnology.com wrote:
On Thu, 23 Dec 2021 02:54:27 +0100, Reinhard Zwirner
reinhard.zwirner@t-online.de> wrote:

Hello,

Due to the used RMS converter low level AC measurememts with this DMM
are less precise to incorrect. There is a lab note as to this problem
by Gellerlabs containing three pictures. I have this note which,
unfortunately, lacks the mentioned pictures. And, unfortunately too,
the link to this note

http://www.gellerlabs.com/34401A%20AC%20zero.htm

doesn\'t work any more. Has anyone of you those pictures and could
provide them? Many thanks in advance.

Regards

Reinhard

That DVM has a huge amount of noise kicked into the front end from the
VF display. They hid that by zeroing AC measurements much below 1 mV.

I like the Fluke better.


The 34401A was my first bench DMM. Bought it in 1998.

I have never calibrated it, could not afford it

This year I went the consultant route, so bought 3 Siglent DMMs. Just for fun, I connected the same references voltage to the 3 Siglent and the 34401A
They measured the same except for minor last digit difference

Not willing to spend on calibrations, the next best thing is to compare to other instruments. Quite unlikely that they would drift in the same direction ?

By the way, I paid a lot for the 34401A, now I can get 4 Siglents for the same price


--
Klaus

I like the 34401, even with some of the faults. As you\'ve seen they\'re
basically accurate forever. Not sure how the new keysigh stuff compares
for long term reliability.

 

[Klaus Kragelund]

23.12.21 21:28, Cydrome Leader wrote:

Klaus Kragelund <klauskvik@hotmail.com> wrote:
23.12.21 03:03, jlarkin@highlandsniptechnology.com wrote:
On Thu, 23 Dec 2021 02:54:27 +0100, Reinhard Zwirner
reinhard.zwirner@t-online.de> wrote:

Hello,

Due to the used RMS converter low level AC measurememts with this DMM
are less precise to incorrect. There is a lab note as to this problem
by Gellerlabs containing three pictures. I have this note which,
unfortunately, lacks the mentioned pictures. And, unfortunately too,
the link to this note

http://www.gellerlabs.com/34401A%20AC%20zero.htm

doesn\'t work any more. Has anyone of you those pictures and could
provide them? Many thanks in advance.

Regards

Reinhard

That DVM has a huge amount of noise kicked into the front end from the
VF display. They hid that by zeroing AC measurements much below 1 mV.

I like the Fluke better.


The 34401A was my first bench DMM. Bought it in 1998.

I have never calibrated it, could not afford it

This year I went the consultant route, so bought 3 Siglent DMMs. Just for fun, I connected the same references voltage to the 3 Siglent and the 34401A
They measured the same except for minor last digit difference

Not willing to spend on calibrations, the next best thing is to compare to other instruments. Quite unlikely that they would drift in the same direction ?

By the way, I paid a lot for the 34401A, now I can get 4 Siglents for the same price


--
Klaus

I like the 34401, even with some of the faults. As you\'ve seen they\'re
basically accurate forever.

At the place I worked before they used it per default. I asked the instrument responsible and he said when they were sent for calibration they were never out of spec. Not even a single instrument. So they prolonged the calibration interval to 2 years


--
Klaus

 

[John Larkin]

On Thu, 23 Dec 2021 20:28:19 -0000 (UTC), Cydrome Leader
<presence@MUNGEpanix.com> wrote:

Klaus Kragelund <klauskvik@hotmail.com> wrote:
23.12.21 03:03, jlarkin@highlandsniptechnology.com wrote:
On Thu, 23 Dec 2021 02:54:27 +0100, Reinhard Zwirner
reinhard.zwirner@t-online.de> wrote:

Hello,

Due to the used RMS converter low level AC measurememts with this DMM
are less precise to incorrect. There is a lab note as to this problem
by Gellerlabs containing three pictures. I have this note which,
unfortunately, lacks the mentioned pictures. And, unfortunately too,
the link to this note

http://www.gellerlabs.com/34401A%20AC%20zero.htm

doesn\'t work any more. Has anyone of you those pictures and could
provide them? Many thanks in advance.

Regards

Reinhard

That DVM has a huge amount of noise kicked into the front end from the
VF display. They hid that by zeroing AC measurements much below 1 mV.

I like the Fluke better.


The 34401A was my first bench DMM. Bought it in 1998.

I have never calibrated it, could not afford it

This year I went the consultant route, so bought 3 Siglent DMMs. Just for fun, I connected the same references voltage to the 3 Siglent and the 34401A
They measured the same except for minor last digit difference

Not willing to spend on calibrations, the next best thing is to compare to other instruments. Quite unlikely that they would drift in the same direction ?

By the way, I paid a lot for the 34401A, now I can get 4 Siglents for the same price


--
Klaus

I like the 34401, even with some of the faults. As you\'ve seen they\'re
basically accurate forever. Not sure how the new keysigh stuff compares
for long term reliability.

We use mostly Keithleys in our test stands. They\'re OK.

I really like my Fluke 8845A. It\'s the winner when you want to measure
a few microvolts.

--

If a man will begin with certainties, he shall end with doubts,
but if he will be content to begin with doubts he shall end in certainties.
Francis Bacon

 

[Cydrome Leader]

Klaus Kragelund <klauskvik@hotmail.com> wrote:

23.12.21 21:28, Cydrome Leader wrote:
Klaus Kragelund <klauskvik@hotmail.com> wrote:
23.12.21 03:03, jlarkin@highlandsniptechnology.com wrote:
On Thu, 23 Dec 2021 02:54:27 +0100, Reinhard Zwirner
reinhard.zwirner@t-online.de> wrote:

Hello,

Due to the used RMS converter low level AC measurememts with this DMM
are less precise to incorrect. There is a lab note as to this problem
by Gellerlabs containing three pictures. I have this note which,
unfortunately, lacks the mentioned pictures. And, unfortunately too,
the link to this note

http://www.gellerlabs.com/34401A%20AC%20zero.htm

doesn\'t work any more. Has anyone of you those pictures and could
provide them? Many thanks in advance.

Regards

Reinhard

That DVM has a huge amount of noise kicked into the front end from the
VF display. They hid that by zeroing AC measurements much below 1 mV.

I like the Fluke better.


The 34401A was my first bench DMM. Bought it in 1998.

I have never calibrated it, could not afford it

This year I went the consultant route, so bought 3 Siglent DMMs. Just for fun, I connected the same references voltage to the 3 Siglent and the 34401A
They measured the same except for minor last digit difference

Not willing to spend on calibrations, the next best thing is to compare to other instruments. Quite unlikely that they would drift in the same direction ?

By the way, I paid a lot for the 34401A, now I can get 4 Siglents for the same price


--
Klaus

I like the 34401, even with some of the faults. As you\'ve seen they\'re
basically accurate forever.

At the place I worked before they used it per default. I asked the
instrument responsible and he said when they were sent for calibration
they were never out of spec. Not even a single instrument. So they
prolonged the calibration interval to 2 years


--
Klaus

Calibration is mostly just a racket, although I completely agree you need
to check instruments to make sure they\'re not broken. I have the hardest
time with stuff like capacitance meters.

As for calibration of things like rulers, I confirmed that yes, I can hand
draw a 1 foot ruler that\'s only 11 inches long on a paper towel and sent
it it for calibration at a metrology lab, and that with the calibration
chart it would be be considered accurate and for a few bucks more I could
claim NIST traceable for my fine instrument. Would it be useful? No, as
long as all the errors are documented, it\'s better than a Starret scale
with no paperwork, at least in the eyes of retarded places ike NASA.