The Keithley model 640 was a vibrating capacitor electrometer. It was available in the 1970's.
Bruce > > On 04 March 2018 at 06:34 george <[email protected]> wrote: > > Hi all > > To the best of my memory Keithley never made vibrating reed > electrometers, the only one that I am aware of is the Varian Cary 401 which > did use Sapphire insulators. I was the European product line specialist for > Varian Cary in the late 1960/1970 era and was involved with the 401. > > George G6HIG > > ________________________________________ > From: volt-nuts <[email protected]> on behalf of > [email protected] <[email protected]> > Sent: 03 March 2018 17:00 > To: [email protected] > Subject: volt-nuts Digest, Vol 103, Issue 3 > > Send volt-nuts mailing list submissions to > [email protected] > > To subscribe or unsubscribe via the World Wide Web, visit > > https://nam02.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.febo.com%2Fcgi-bin%2Fmailman%2Flistinfo%2Fvolt-nuts&data=02%7C01%7C%7Cb5818846d36e4ecd914908d581283c52%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C636556932161076932&sdata=cp01qd%2FkRw4yYSLYOqJ8RwUF8oOxtdqLVOmDal7gBhs%3D&reserved=0 > > https://nam02.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.febo.com%2Fcgi-bin%2Fmailman%2Flistinfo%2Fvolt-nuts&data=02%7C01%7C%7Cb5818846d36e4ecd914908d581283c52%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C636556932161076932&sdata=cp01qd%2FkRw4yYSLYOqJ8RwUF8oOxtdqLVOmDal7gBhs%3D&reserved=0 > or, via email, send a message with subject or body 'help' to > [email protected] > > You can reach the person managing the list at > [email protected] > > When replying, please edit your Subject line so it is more specific > than "Re: Contents of volt-nuts digest..." > > Today's Topics: > > 1. Re: Precision high resistance measurements / calibration of > HP 4339B high-resistance meter. (ed breya) > 2. Re: Precision high resistance measurements / calibration of > HP 4339B high-resistance meter. (Mitch Van Ochten) > > ---------------------------------------------------------------------- > > Message: 1 > Date: Fri, 2 Mar 2018 09:22:32 -0800 > From: ed breya <[email protected]> > To: [email protected] > Subject: Re: [volt-nuts] Precision high resistance measurements / > calibration of HP 4339B high-resistance meter. > Message-ID: <[email protected]> > Content-Type: text/plain; charset=utf-8; format=flowed > > Oops - I think I didn't send this message properly yesterday - here goes > again. Ed > > Yes, David, unless you go to very extreme measures, you won't see real R > values that have any practical meaning beyond E12 ohms or so. Most > practical insulation Rs may be around E12-E14 tops, unless you go to > sapphire. Up in that region, the R may be all within a material, or > include surface components like a film of dirt or moisture, or a > fingerprint. > > E11 resistors can be made to fairly high precision, and maybe E12 > nowadays. In the old days, higher values were made by stacking E11s - > like ten in series to get E12 with decent precision. The glass packaging > also limits how high it can go, due to leakage within and on the > surface. I once used a glass reed relay capsule as an ultra-high > resistance in a circuit. There was no precision or stability at all, but > it made a nice high resistor (probably E14-ish dry) even though there > was no element in there, and the circuit didn't care, as long as it was > very high, but not infinite. > > The specs on this HP unit are likely just the most extreme capability > taking maximum voltage over minimum current resolution, but any > measurements would tend to be very noisy and unstable anyway. Also, > testing at the extreme 1 kV makes the numbers seem more impressive, but > the voltage coefficient of resistance will pretty much be unpredictable. > > If this is a digital meter, then the other spec trick that tends to > obscure the real performance limit is that the ultimate resolution and > noise is that last digit - or even last two or three - that may may be > pretty jumpy, unless very long averaging time is used. > > There may be newer, fancier electrometers nowadays, but Keithley used to > be the standard for these in the old days, before several digits of DVM > resolution complicated the specs. They had a vibrating capacitor > electrometer with all-sapphire input structure back in the 1970s/80s I > think, that was the epitome of electrometers. I forget the model number, > but vaguely recall that it could reach the aA region full scale - not > that last digit of resolution thing. It's long obsolete, and I don't > think they ever made anything actually better - only added DVM digits to > less capable, conventional semiconductor amplifier techniques. If you > can find info on it, it's an interesting read. I found a pdf of the > manual years ago, but have no idea where it is now, or what info may > still be around. > > Ed > > ------------------------------ > > Message: 2 > Date: Fri, 2 Mar 2018 20:41:10 -0500 > From: "Mitch Van Ochten" <[email protected]> > To: "'Discussion of precise voltage measurement'" <[email protected]> > Subject: Re: [volt-nuts] Precision high resistance measurements / > calibration of HP 4339B high-resistance meter. > Message-ID: <[email protected]> > Content-Type: text/plain; charset="UTF-8" > > Here are specs from an older General Radio Bridge for observation. > > GR 1644-A specifications: > > Resistance Range: 1 kΩ to 1000 TΩ (10^3 to 10^15 Ω) in ten ranges. > Accuracy: 10^3 Ω to 10^10 Ω, ±1 %. After self-calibration: 10^10 to > 10^12 Ω, ±1%*; 10^13 Ω, ±2%; 10^14 Ω, ±10%; 10^15 Ω, ± one scale > division. > ΔR% Dial: ±5% range; accurate to ±0.2% or, for small changes, > to ±0.1%. > Test Voltage: Voltage accuracy is ±3% ±0.5 V. > Fixed Voltages** 10 20 50 100 200 500 1000 v > > Best regards, > > mitch > > -----Original Message----- > From: volt-nuts [mailto:[email protected]] On Behalf Of ed breya > Sent: Friday, March 02, 2018 12:23 PM > To: [email protected] > Subject: Re: [volt-nuts] Precision high resistance measurements / > calibration of HP 4339B high-resistance meter. > > Oops - I think I didn't send this message properly yesterday - here goes > again. Ed > > Yes, David, unless you go to very extreme measures, you won't see real R > values that have any practical meaning beyond E12 ohms or so. Most practical > insulation Rs may be around E12-E14 tops, unless you go to sapphire. Up in > that region, the R may be all within a material, or include surface > components like a film of dirt or moisture, or a fingerprint. > > E11 resistors can be made to fairly high precision, and maybe E12 > nowadays. In the old days, higher values were made by stacking E11s - like > ten in series to get E12 with decent precision. The glass packaging also > limits how high it can go, due to leakage within and on the surface. I once > used a glass reed relay capsule as an ultra-high resistance in a circuit. > There was no precision or stability at all, but it made a nice high resistor > (probably E14-ish dry) even though there was no element in there, and the > circuit didn't care, as long as it was very high, but not infinite. > > The specs on this HP unit are likely just the most extreme capability > taking maximum voltage over minimum current resolution, but any measurements > would tend to be very noisy and unstable anyway. Also, testing at the extreme > 1 kV makes the numbers seem more impressive, but the voltage coefficient of > resistance will pretty much be unpredictable. > > If this is a digital meter, then the other spec trick that tends to > obscure the real performance limit is that the ultimate resolution and noise > is that last digit - or even last two or three - that may may be pretty > jumpy, unless very long averaging time is used. > > There may be newer, fancier electrometers nowadays, but Keithley used to > be the standard for these in the old days, before several digits of DVM > resolution complicated the specs. They had a vibrating capacitor electrometer > with all-sapphire input structure back in the 1970s/80s I think, that was the > epitome of electrometers. I forget the model number, but vaguely recall that > it could reach the aA region full scale - not that last digit of resolution > thing. It's long obsolete, and I don't think they ever made anything actually > better - only added DVM digits to less capable, conventional semiconductor > amplifier techniques. If you can find info on it, it's an interesting read. I > found a pdf of the manual years ago, but have no idea where it is now, or > what info may still be around. > > Ed > > _______________________________________________ > volt-nuts mailing list -- [email protected] To unsubscribe, go to > https://nam02.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.febo.com%2Fcgi-bin%2Fmailman%2Flistinfo%2Fvolt-nuts&data=02%7C01%7C%7Cb5818846d36e4ecd914908d581283c52%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C636556932161076932&sdata=cp01qd%2FkRw4yYSLYOqJ8RwUF8oOxtdqLVOmDal7gBhs%3D&reserved=0 > > https://nam02.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.febo.com%2Fcgi-bin%2Fmailman%2Flistinfo%2Fvolt-nuts&data=02%7C01%7C%7Cb5818846d36e4ecd914908d581283c52%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C636556932161076932&sdata=cp01qd%2FkRw4yYSLYOqJ8RwUF8oOxtdqLVOmDal7gBhs%3D&reserved=0 > and follow the instructions there. > > ------------------------------ > > Subject: Digest Footer > > _______________________________________________ > volt-nuts mailing list > [email protected] > > https://nam02.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.febo.com%2Fcgi-bin%2Fmailman%2Flistinfo%2Fvolt-nuts&data=02%7C01%7C%7Cb5818846d36e4ecd914908d581283c52%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C636556932161076932&sdata=cp01qd%2FkRw4yYSLYOqJ8RwUF8oOxtdqLVOmDal7gBhs%3D&reserved=0 > > https://nam02.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.febo.com%2Fcgi-bin%2Fmailman%2Flistinfo%2Fvolt-nuts&data=02%7C01%7C%7Cb5818846d36e4ecd914908d581283c52%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C636556932161076932&sdata=cp01qd%2FkRw4yYSLYOqJ8RwUF8oOxtdqLVOmDal7gBhs%3D&reserved=0 > > ------------------------------ > > End of volt-nuts Digest, Vol 103, Issue 3 > > ***************************************** > > _______________________________________________ > volt-nuts mailing list -- [email protected] > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts > and follow the instructions there. > _______________________________________________ volt-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
