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
Low level AC measuremets with HP 34401
Started by ●December 22, 2021
Reply by ●December 22, 20212021-12-22
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 > > Reinhardgoogle 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
Reply by ●December 22, 20212021-12-22
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 > >ReinhardThat 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
Reply by ●December 22, 20212021-12-22
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
Reply by ●December 22, 20212021-12-22
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.pdfIt'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.
Reply by ●December 23, 20212021-12-23
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>
Reply by ●December 23, 20212021-12-23
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
Reply by ●December 23, 20212021-12-23
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
Reply by ●December 23, 20212021-12-23
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 > > > -- > KlausI 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.
Reply by ●December 23, 20212021-12-23
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
