Re: [volt-nuts] Precision high resistance measurements / calibration of HP 4339B high-resistance meter.
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:volt-nuts-boun...@febo.com] On Behalf Of ed breya Sent: Friday, March 02, 2018 12:23 PM To: volt-nuts@febo.com 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 -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there. ___ 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.
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 -- volt-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
Re: [volt-nuts] Precision high resistance measurements / calibration of HP 4339B high-resistance meter. Fix?
On 2 March 2018 at 09:22, Andre wrote: > Maybe one bad resistor? I've read that tin whiskering can occur even on > relatively recent equipment, slower than lead free but still a problem. > I'd do a visual inspection just to see, shouldn't be an issue. > -A > An issue with fingerprints would not totally surprise me. It is obvious the seller had multiple meters, which were sent to a lab, which I am suspicious of*. The seller said the lab would have swapped pieces between units to try to get one working. He had at least 3. 1) My one, which has a recent(ish) Agilent serial number, and Agilent written on the back, but an HP front panel. 2) Another which has HP on the back, but an Agilent front panel. 3) Another said to be working. * I consider is lab suspicious, the fact mine was sold as having no output, yet there was output, and it was within spec. It could be an intermittent fault of course. So its almost certain bits have been swapped between different units. It is is finger prints, what would be the best way to remove them? I see some say IPA, but others have said that can disolve solder resist. I once had a Sun workstation which had one of the covers missing of the back where sbus expansion cards https://en.wikipedia.org/wiki/SBus were supposed to be put. This was stored in the garage. Some mice decided this Sun would make a nice home, and used it as a toilet! Needles to say the board was covered in what mice excrete. After various attempts to get it back to life, an hour or so in the bath with plain tap water did work. But of course very low currents of the 4339B would prevent different challenges to a digital board, where signals are either 0 or 1. But whilst the 4339B may not be free of finger prints, it has not been used as a mouse loo. So if it does require cleaning, it should be fairly modest, but I have no idea what to use. I buy a IPA on eBay for cleaning, which is claimed to be 99.9% pure, but I doubt it is really that pure, so if IPA was used, I would buy from a proper chemical supplier. Dave ___ 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.
Re: [volt-nuts] Precision high resistance measurements / calibration of HP 4339B high-resistance meter. Fix?
Maybe one bad resistor? I've read that tin whiskering can occur even on relatively recent equipment, slower than lead free but still a problem. I'd do a visual inspection just to see, shouldn't be an issue. -A From: volt-nuts on behalf of Dr. David Kirkby Sent: 02 March 2018 03:16:24 To: Discussion of precise voltage measurement Subject: [volt-nuts] Precision high resistance measurements / calibration of HP 4339B high-resistance meter. I pickup up an HP/Agilent (front says HP, rear says Agilent) 4339B high-resistance meter from eBay. The 4339B has an internal supply up to 1000 V, an ammeter to measure current, and obviously computes resistance from Ohms Law. It is supposed to work up to 16 Peta ohms (1.6x10^16 ohms), which would pass a current of 62.5 fA with 1000 V. It was sold as non-working, with no output. Even attempting to get some output was challenging as it had an obscure 6-pin interlock connector, and there's no information in the manual about this. It also has a trixaxial input connector with a screw thread. I asked Keysight for some information about the connectors. I still don't know what the triaxial connector is, but I have the interlock sussed - a HiroseHR10A-7P-6P(73) plug fits, and there's some information about the wiring of this in the manual for the 11617C low-noise test leads. Keysight offered to do a free technical evaluation, so I thought I'd take them up on it, rather than waste too much time trying myself to get it working. It was sent to Keysight and they sent me a report showing there is output voltage, despite it being sold as having no output, and the output is all in spec. Unfortunately, it was out of spec on one of the current ranges. It is reading 0.082 nA low with a test current of 10 nA, but the specification is +/- 0.063 nA. So it is only a little bit out, but it is still out of spec. Test currents of 100 pA, 1 nA, 10 nA, 100 nA, 1 uA, 10 uA and 100 uA were used, so the 10 nA is neither at the low nor high end of the range of the meter. When I received an email copy of the free technical report, I assumed the 4339B had not been subjected to a full calibration as it was only tested with resistors up to 10^11 ohms, but it is supposed to read resistance up to 1.6 x 10^16 ohm, so the highest value resistor used during the technical evualation is 5 orders of magnitude lower than the what the meter can read. Also the meter was only tested at 100 V when reading resistors, whereas I would have thought it more sensible to test at a higher voltage, given it can output 1 kV. I decided to pay Keysight for a full calibration, so I got a cal certificate, which shows the out of spec reading. http://www.kirkbymicrowave.co.uk/tmp/1-9690444179-1-combined-file.pdf I was rather hoping the cal certificate would have some extra readings, but I actually received no more technical information than Keysight had given me for nothing, although they did update the firmware as I requested. I have two questions. 1) Is 10^11 ohms a practical limit on making resistors that can be used for calibration purposes? I don't know what the Keysight uncertainty on their calibration standards are, so maybe 10^11 ohms is all its practical to make. 2) Does anyone know if the meter can be adjusted on individual ranges? I find it a bit hard to believe that given the ammeter was tested with currents covering 6 orders of magnitude (100 pA to 100 uA), that there's no adjustment on individual ranges. I doubt that it is possible to design a circuit to cover that range, without switching in some different resistors at some point. But I'm told it can't be adjusted, and needs a new board. I'm wondering if anyone knows anything about this meter, just in case Keysight are wrong. I know they should not be, but it is not a current instrument, so it's just possible the engineer did not know it could be adjusted. Dr David Kirkby Ph.D C.Eng MIET Kirkby Microwave Ltd Registered office: Stokes Hall Lodge, Burnham Rd, Althorne, Chelmsford, Essex, CM3 6DT, United Kingdom Registered in England and Wales as company number 08914892 http://www.kirkbymicrowave.co.uk/ Tel 01621'680100 / +44 1621-680100 ___ 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. ___ 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.
