[volt-nuts] volt-nuts Digest, Vol 83, Issue 11

Tue Jul 19 12:02:24 EDT 2016

http://boston.craigslist.org/bmw/ele/5687633175.html

On Tue, Jul 19, 2016 at 12:00 PM, <volt-nuts-request at febo.com> wrote:

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> Today's Topics:
>
>    1. Re: Keysight 3458A vs Keithley 2002 8.5 digit     multimeters.
>       (John Phillips)
>    2. Re: Keysight 3458A vs Keithley 2002 8.5 digit     multimeters.
>       (Dr. David Kirkby (Kirkby Microwave Ltd))
>    3. Re: Keysight 3458A vs Keithley 2002 8.5 digit     multimeters.
>       (John Phillips)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Mon, 18 Jul 2016 09:34:18 -0700
> From: John Phillips <john.phillips0 at gmail.com>
> To: illya at xdevs.com,  Discussion of precise voltage measurement
>         <volt-nuts at febo.com>
> Subject: Re: [volt-nuts] Keysight 3458A vs Keithley 2002 8.5 digit
>         multimeters.
> Message-ID:
>         <
> CANEyv6bhoQHdui3m9i_AbothnDG3rFATFqHDgzMJoPE69+G9UA at mail.gmail.com>
> Content-Type: text/plain; charset=UTF-8
>
> Most labs never turn 3458As off. The longer they are on the lower the drift
> rate. I would rather have an 20 year old meter with new batteries than a
> new meter.
>
> On Mon, Jul 18, 2016 at 4:11 AM, Illya Tsemenko <illya at xdevs.com> wrote:
>
> > Well, it's the topic many can go on and on about.
> > As with everything there are specific cons and pros of both units, but
> > here are my 5c:
> > + K2002 is smaller, lighter (4kg vs 10kg), less powerhungry (sometimes
> > it's important if you send unit for cal overseas, or take to remote
> site).
> > + K2002 can support scan cards (standard, or low-EMF ones) via expansion
> > slot
> > + K2002 DCI/ACI goes up to 2Amps
> > + K2002 goes bit higher on ACV frequency (15MHz, but performance there is
> > so-so)
> > + K2002 natively supports thermocouples, RTDs, SPRT thermal sensors and
> > custom settings
> > + K2002 supports rare rainbow unicorn nanovolt preamplifier Keithley 1801
> > (substitute can be bodged up but that's not beginner's project)
> > - Old K2002's require capacitor replacements (units with S/N 06xxxxx and
> > 05xxxxx). Mandatory! Meters from 2005+ year have S/N starting with
> 11xxxxx
> > - Readings noisier than 3458A
> > I have two units in use, and have worklogs for both :
> > https://xdevs.com/review/kei2002/ - newer K2002 from year 2007
> > https://xdevs.com/fix/kei2002_u2/ - older K2002 from 1994 which was
> > repaired after capacitor leak damage.
> > Service of these Keithley meters (and 2001, which are very similar
> design)
> > is not complicated, but require attention and knowledge what you doing.
> > There only few custom parts used.
> >
> > Now regarding industry standard 3458A. Reason why you saw only 3458A in
> > metrology lab is simple:
> > Superior ADC (many rightfully think it's best on market, ever), amazing
> > linearity (JJA was required to test linearity with good confidence), very
> > easy calibration (just need 10V reference and 10KOhm standard resistor to
> > get 3458A calibrated to uncertainty of used standards), Artifact
> > calibration (ACAL) to significantly remove impact of temperature
> variation
> > on accuracy, proven performance. Many labs use 3458A as main transfer
> > standard due to it's ADC performance.
> >
> > It comes at cost though, as key components of meter's A/D are custom
> > hybrids. Meaning if you got sour pill, and A/D drifting, you will have to
> > replace expensive A/D board. Newer Agilent/Keysight branded 3458A's are
> > essentially same boxes, just with newer hardware and likely with new
> > FPGA-based digital brains. Performance is same though, unless you really
> > getting early 1990's meter. Many design issues and items I got covered in
> > my repair worklog: https://xdevs.com/fix/hp3458a/
> >
> > Brief 10V comparison : https://xdevs.com/datalog_tcomp/ - sampling 10V
> > connected to 2001+2002+3458A
> > Some of the A/D noise comparisons (meter input shorted) -
> > https://xdevs.com/article/dmm_noise/
> >
> > So decide what fit best your needs. 3458A is overall higher performance
> > instrument, but in lot of applications outside of metrology it's
> > performance benefits may not cover up for higher price and size. Both
> 3458A
> > and 2002 are still supported and sold new by manufacturers. Regular
> > calibration of these is likely be over 1000$USD, and lab-grade
> calibration
> > for 3458A is usually in range of 2600$USD.
> >
> > P.S. there are also few other 8.5d meters, but much less information
> > available on those, as less people have them. Only "modern" 8.5d meter is
> > 8508A, which cost even more than 3458A without much performance
> improvement.
> >
> > 18/07/16 17:54, Dr. David Kirkby (Kirkby Microwave Ltd) пишет:
> >
> > I am interested to hear people's view on the relative merits  of the
> >> HP/Agilent/ Keysight 3458A vs the Keithley 2002.
> >>
> >> I noticed that when I recently visit the standard lab for voltage at
> NPL,
> >> the place was littered with Agilent 3458As, but I did not notice a
> single
> >> Keithley 2002. But maybe NPL get better discounts from HP/Agilent
> Keysight
> >> than Keithley/Tektronix.
> >>
> >> I notice that the used prices of 3458A is higher than 2002s.
> >>
> >> Also, are there any things ons should be looking out for when buying a
> >> 3458A or 2002? I have in the past thought an Agilent front panel was a
> >> better than an HP one, as it would not be as old, but this is not always
> >> true - see my comment later.
> >>
> >> What S/N are best avoided? Does anyone have a record of S/Ns of Keighley
> >> meters with time?
> >>
> >> Very recently I had a somewhat scruffy HP 6674A PSU with a damaged LCD.
> It
> >> cost me $50 or so to pick up a clean Agilent front panel with a new
> >> display.  The display actually turned out to be unsuitable,  yet my
> >> Agilent
> >> badged 6674A is actually a fairly old HP unit.  So white my intention
> was
> >> not to rebadge the PSU, that happened as a result of a legitimate reason
> >> to
> >> get it working. So this really indicates how an old HP 3457A could be
> made
> >> to look a newer Agilent one.
> >>
> >> Dave.
> >> _______________________________________________
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> >> and follow the instructions there.
> >>
> >
> >
> >
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>
>
>
> --
>
> *John Phillips*
>
>
> ------------------------------
>
> Message: 2
> Date: Mon, 18 Jul 2016 19:48:35 +0100
> From: "Dr. David Kirkby (Kirkby Microwave Ltd)"
>         <drkirkby at kirkbymicrowave.co.uk>
> To: Discussion of precise voltage measurement <volt-nuts at febo.com>
> Subject: Re: [volt-nuts] Keysight 3458A vs Keithley 2002 8.5 digit
>         multimeters.
> Message-ID:
>         <CANX10hCBO9MMxwaT0E6HbumWrP+pW3=
> DkX4MQ88Ux2m3zKnOCA at mail.gmail.com>
> Content-Type: text/plain; charset=UTF-8
>
> On 18 Jul 2016 17:34, "John Phillips" <john.phillips0 at gmail.com> wrote:
> >
> > Most labs never turn 3458As off. The longer they are on the lower the
> drift
> > rate. I would rather have an 20 year old meter with new batteries than a
> > new meter.
>
> If one buys a used meter, one has no idea if it has been switched on very
> occasionally or on 24/7.
>
> Do you keep your meter powered up during the transit between your lab and
> the cal lab? I would think that quite difficult if you used a courier,  but
> not a problem if it was taken in a car.
>
> Dave.
>
>
> ------------------------------
>
> Message: 3
> Date: Mon, 18 Jul 2016 12:39:33 -0700
> From: John Phillips <john.phillips0 at gmail.com>
> To: Discussion of precise voltage measurement <volt-nuts at febo.com>
> Subject: Re: [volt-nuts] Keysight 3458A vs Keithley 2002 8.5 digit
>         multimeters.
> Message-ID:
>         <CANEyv6a9Y_69qFSZnRVcEL4sKDAFsnx-PYw93=
> YproE1hww+QQ at mail.gmail.com>
> Content-Type: text/plain; charset=UTF-8
>
> We do not keep them powered up for transit.
> All the meter gets more stable with age. The reference gets more stable
> with burn in.
> We store 3458As energised even when we do not plan to use them for a while.
> Most 10 year old meters are as stable as the new meters with the high
> stability option.
> I do not have any stats but quite often we would buy an old meter that had
> a old cal sticker and find that 10 volse was still in spec.
>
>
> On Mon, Jul 18, 2016 at 11:48 AM, Dr. David Kirkby (Kirkby Microwave Ltd) <
> drkirkby at kirkbymicrowave.co.uk> wrote:
>
> > On 18 Jul 2016 17:34, "John Phillips" <john.phillips0 at gmail.com> wrote:
> > >
> > > Most labs never turn 3458As off. The longer they are on the lower the
> > drift
> > > rate. I would rather have an 20 year old meter with new batteries than
> a
> > > new meter.
> >
> > If one buys a used meter, one has no idea if it has been switched on very
> > occasionally or on 24/7.
> >
> > Do you keep your meter powered up during the transit between your lab and
> > the cal lab? I would think that quite difficult if you used a courier,
> but
> > not a problem if it was taken in a car.
> >
> > Dave.
> > _______________________________________________
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> >
>
>
>
> --
>
> *John Phillips*
>
>
> ------------------------------
>
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>
> End of volt-nuts Digest, Vol 83, Issue 11
> *****************************************
>