Re: [volt-nuts] Would you be concerned if the manufacturer does not have an uncertainty budget, so can't provide uncertainties in a calibration?
On Tue, 24 Apr 2018, 05:37 Florian Teply, wrote: > probably I didn't get my wording precise. Just as you say, it looks > like they assume the resistors should have nominal value. Otherwise > they would need to list what they assume to be the nominal value, which > they don't. I was referring to the last column where they list the > measured deviation of +0.0107e11. In any case, I would consider unknown > resistances pretty odd as that would render the whole effort of > having 8.5 digits in the first place useless... So the only > explanation that would make sense is that the resistors should habve > nominal values. Unless of course the have individual values from > manufacture stored somewhere. But then it also wouldn't make sense to > not tell the owner of the device... > The meter sent for calibration was a 4339B. That's a 5.5 digit high resistance, not an 8.5 digit one. > > They don't spell out explicitlyy whether the test limits they give, > i.e. here +/- 0.0573e11 ohms would be their own measurement > uncvertainty or the instruments spec limits, but given the odd numbers > I'd expect it to be their measurement uncertainty. > > Best regards, > Florian My interpretation is the numbers in the last column are the *difference* between what Keysight believe is the correct value and what my meter read. If you look on page 5, on Current Measurement Accuracy Test, you will see for the 10 nA range, you will see test limits of +/- 0.063 nA and test results of -.082 nA - so a failure. The meter is going off to Keysight (UK) tomorrow. They may ore many not send it to the USA, as they are waiting to hear from the USA whether they can provide uncertainties. 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] Would you be concerned if the manufacturer does not have an uncertainty budget, so can't provide uncertainties in a calibration?
Am Mon, 23 Apr 2018 23:59:57 +0100 schrieb "Dr. David Kirkby" : > On 21 April 2018 at 09:32, Florian Teply wrote: > > > Am Fri, 20 Apr 2018 14:37:22 +0100 > > schrieb "Dr. David Kirkby" : > > > > > The columns below, from left to right are > > > > > > Device type (whether the DUT is floating, or grounded one side). > > > Resistor setting (ohms) > > > Votage (V) > > > Measurement time (Long or Short) > > > Test limits (+/- ohm) > > > Test results (ohm) > > > > > > FLOAT 1E6 100 SHORT +/- 0.0086E6 -.0019E6 > > > FLOAT 1E7 100 LONG +/- 0.0063E7 -.0016E7 > > > FLOAT 1E8 100 LONG +/- 0.0073E8 -.0027E8 > > > FLOAT 1E9 100 LONG +/- 0.0093E9 -.0032E9 > > > FLOAT 1E10 100 LONG +/- 0.0273E10 +.0095E10 > > > FLOAT 1E11 100 LONG +/- 0.0453E11 +.0080E11 > > > FLOAT 1E11 100 SHORT +/- 0.0550E11 +.0086E11 > > > FLOAT 1E11 10 LONG +/- 0.0546E11 +.0113E11 > > > GROUND 1E7 100 LONG +/- 0.0065E7 -.0017E7 > > > GROUND 1E11 10 LONG +/- 0.0573E11 +.0107E11 > > > > > > That strikes me that the assumption is the values are what their > > > nominal values are, but I wonder how accurate they are. > > > > > I might be wrong, but to me it seems like the resistors are not > > exactly nominal but slightly off. But the uncertainty of the > > measurements is larger than the deviation. Or were you referring to > > the notion that the uncertainties are symmetrically distributed? > > I'd be pretty surprised if the uncertainties were asymmetrical for > > that matter. > > > how do you determine that the resistors are not assumed to be the > nominal value? > > As far as I can see, taking the example of a 1e11 ohm resistor > grounded at one end (very last entry on table), the meter should read > 1e11 +/- 0.0573e11 ohms. My meter read 0.010e11 ohms high, so was in > spec, as 0.010e11 is less than 0.0573e11. As far as I can determine, > the fact the permissable range of the meter is +/-x, rather than +x, > -y, means the nominal values are assumed. > Ah, probably I didn't get my wording precise. Just as you say, it looks like they assume the resistors should have nominal value. Otherwise they would need to list what they assume to be the nominal value, which they don't. I was referring to the last column where they list the measured deviation of +0.0107e11. In any case, I would consider unknown resistances pretty odd as that would render the whole effort of having 8.5 digits in the first place useless... So the only explanation that would make sense is that the resistors should habve nominal values. Unless of course the have individual values from manufacture stored somewhere. But then it also wouldn't make sense to not tell the owner of the device... They don't spell out explicitlyy whether the test limits they give, i.e. here +/- 0.0573e11 ohms would be their own measurement uncvertainty or the instruments spec limits, but given the odd numbers I'd expect it to be their measurement uncertainty. Best regards, Florian ___ 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] Would you be concerned if the manufacturer does not have an uncertainty budget, so can't provide uncertainties in a calibration?
On 21 April 2018 at 09:32, Florian Teply wrote: > Am Fri, 20 Apr 2018 14:37:22 +0100 > schrieb "Dr. David Kirkby" : > > > The columns below, from left to right are > > > > Device type (whether the DUT is floating, or grounded one side). > > Resistor setting (ohms) > > Votage (V) > > Measurement time (Long or Short) > > Test limits (+/- ohm) > > Test results (ohm) > > > > FLOAT 1E6 100 SHORT +/- 0.0086E6 -.0019E6 > > FLOAT 1E7 100 LONG +/- 0.0063E7 -.0016E7 > > FLOAT 1E8 100 LONG +/- 0.0073E8 -.0027E8 > > FLOAT 1E9 100 LONG +/- 0.0093E9 -.0032E9 > > FLOAT 1E10 100 LONG +/- 0.0273E10 +.0095E10 > > FLOAT 1E11 100 LONG +/- 0.0453E11 +.0080E11 > > FLOAT 1E11 100 SHORT +/- 0.0550E11 +.0086E11 > > FLOAT 1E11 10 LONG +/- 0.0546E11 +.0113E11 > > GROUND 1E7 100 LONG +/- 0.0065E7 -.0017E7 > > GROUND 1E11 10 LONG +/- 0.0573E11 +.0107E11 > > > > That strikes me that the assumption is the values are what their > > nominal values are, but I wonder how accurate they are. > > > I might be wrong, but to me it seems like the resistors are not > exactly nominal but slightly off. But the uncertainty of the > measurements is larger than the deviation. Or were you referring to the > notion that the uncertainties are symmetrically distributed? I'd be > pretty surprised if the uncertainties were asymmetrical for that > matter. > > Best regards, > Florian > Florian, how do you determine that the resistors are not assumed to be the nominal value? As far as I can see, taking the example of a 1e11 ohm resistor grounded at one end (very last entry on table), the meter should read 1e11 +/- 0.0573e11 ohms. My meter read 0.010e11 ohms high, so was in spec, as 0.010e11 is less than 0.0573e11. As far as I can determine, the fact the permissable range of the meter is +/-x, rather than +x, -y, means the nominal values are assumed. I put the complete cal certificate here. http://www.kirkbymicrowave.co.uk/tmp/1-9690444179-1-combined-file.pdf What I also find a bit odd, is the 16340A RC box used for calibrating the meter, is itself not due for calibration for over a year. I am awaiting a call/email from the calibration manager at Keysight (UK), and I've been advised Keysight (UK) have contacted Keysight in the USA to see what they can provide, as a calibration *with* uncertainties is listed on the Keysight (USA) website. I have no formal requirement for needing the uncertainties, but I am a bit worried the fact that Keysight (UK) seem to use a resistance box that is calibrated less than once/year, and can't provide the uncertainties, and as far as I can tell (although you disagree), it would appear the nominal value of the resistors are used. . It does not exactly inspire a lot of confidence. 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] Would you be concerned if the manufacturer does not have an uncertainty budget, so can't provide uncertainties in a calibration?
Am Fri, 20 Apr 2018 14:37:22 +0100 schrieb "Dr. David Kirkby" : > 2) Measure the resistors in the 16340A. What puzzles me here, is that > when I had another 4339B calibrated, the limits on measuring those > resistors were symmetrical about the nominal values of 1e6, 1e7, 1e8, > 1e8, 1e10 and 1e11 ohms. I would have expected the limits to be > asymmetrical, because those resistors are probably not their nominal > value. > > The columns below, from left to right are > > Device type (whether the DUT is floating, or grounded one side). > Resistor setting (ohms) > Votage (V) > Measurement time (Long or Short) > Test limits (+/- ohm) > Test results (ohm) > > FLOAT 1E6 100 SHORT +/- 0.0086E6 -.0019E6 > FLOAT 1E7 100 LONG +/- 0.0063E7 -.0016E7 > FLOAT 1E8 100 LONG +/- 0.0073E8 -.0027E8 > FLOAT 1E9 100 LONG +/- 0.0093E9 -.0032E9 > FLOAT 1E10 100 LONG +/- 0.0273E10 +.0095E10 > FLOAT 1E11 100 LONG +/- 0.0453E11 +.0080E11 > FLOAT 1E11 100 SHORT +/- 0.0550E11 +.0086E11 > FLOAT 1E11 10 LONG +/- 0.0546E11 +.0113E11 > GROUND 1E7 100 LONG +/- 0.0065E7 -.0017E7 > GROUND 1E11 10 LONG +/- 0.0573E11 +.0107E11 > > That strikes me that the assumption is the values are what their > nominal values are, but I wonder how accurate they are. > I might be wrong, but to me it seems like the resistors are not exactly nominal but slightly off. But the uncertainty of the measurements is larger than the deviation. Or were you referring to the notion that the uncertainties are symmetrically distributed? I'd be pretty surprised if the uncertainties were asymmetrical for that matter. Best regards, Florian ___ 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] Would you be concerned if the manufacturer does not have an uncertainty budget, so can't provide uncertainties in a calibration?
On 19 April 2018 at 16:42, wrote: > -a calibration certificate without uncertainsties is totally useless. in > is not even a calibration. > -I have never understood why people are so keen on getting things > calibrated at Keysight. > I must admit I do have some concerns, about this. There are 3 aspects to the calibration 1) Calibrate the voltage of the internal source using a 3458A. I have no concerns a 3458A is not more than capable of measuring the voltage. 2) Measure the resistors in the 16340A. What puzzles me here, is that when I had another 4339B calibrated, the limits on measuring those resistors were symmetrical about the nominal values of 1e6, 1e7, 1e8, 1e8, 1e10 and 1e11 ohms. I would have expected the limits to be asymmetrical, because those resistors are probably not their nominal value. The columns below, from left to right are Device type (whether the DUT is floating, or grounded one side). Resistor setting (ohms) Votage (V) Measurement time (Long or Short) Test limits (+/- ohm) Test results (ohm) FLOAT 1E6 100 SHORT +/- 0.0086E6 -.0019E6 FLOAT 1E7 100 LONG +/- 0.0063E7 -.0016E7 FLOAT 1E8 100 LONG +/- 0.0073E8 -.0027E8 FLOAT 1E9 100 LONG +/- 0.0093E9 -.0032E9 FLOAT 1E10 100 LONG +/- 0.0273E10 +.0095E10 FLOAT 1E11 100 LONG +/- 0.0453E11 +.0080E11 FLOAT 1E11 100 SHORT +/- 0.0550E11 +.0086E11 FLOAT 1E11 10 LONG +/- 0.0546E11 +.0113E11 GROUND 1E7 100 LONG +/- 0.0065E7 -.0017E7 GROUND 1E11 10 LONG +/- 0.0573E11 +.0107E11 That strikes me that the assumption is the values are what their nominal values are, but I wonder how accurate they are. 3) Apply known currents, again using the test box. I've asked Keysight if they are certain that the meter can be put within specification, and if not whether it might be sent outside the UK to be calibrated. To be honest, I don't really NEED the uncertainties, but the fact they can't provide them does concern me a bit. 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.
Re: [volt-nuts] Would you be concerned if the manufacturer does not have an uncertainty budget, so can't provide uncertainties in a calibration?
understand, it is maybe different here in Germany then, there are a number of labs with pretty low uncertainties who also support old gear adjustments. on the other hand, you have to know who you are working with for what gear. Otherwise you can have unpleasant surprises. in your case, if you have no nobody calibrating your meter with a specified uncertainty, maybe an option is to build your own decade of resistances and use a precisiion high voltage source (calibrator) and a 3458A as current meter. that brings you to say 10nA/100Gohms. if thats sufficient. > Gesendet: Donnerstag, 19. April 2018 um 18:41 Uhr > Von: "Dr. David Kirkby" > An: "Discussion of precise voltage measurement" > Betreff: Re: [volt-nuts] Would you be concerned if the manufacturer does not > have an uncertainty budget, so can't provide uncertainties in a calibration? > > On 19 April 2018 at 16:42, wrote: > > > -a calibration certificate without uncertainsties is totally useless. in > > is not even a calibration. > > > > Having bought the meter, it is not so useless if it tells me it is working > or not, but I do have some concerns I must admit. > > > > -I have never understood why people are so keen on getting things > > calibrated at Keysight. > > > > Well, quite simply there's nobody else I would trust to calibrate much of > the Agilent equipment. I did contact one UKAS acredited lab, who quoted to > calibrate loads of bits of my equipment, but declined this meter. But when > I checked the companies uncertainties, I was totally unimpressed. For > example, their uncertainty on capacitance at 1 MHz was well in excess of > 0.05%, yet they quoted to calibrate the meter, which has a basic > uncertainty of 0.05%. I also found their prices were much higher than > Keysight. > > Most companies are not going to be able to adjust Agilent stuff if it is > out of spec anyway, as often the software to make the adjustments is not > available. So I'm not convinced there is any half-sensible alternative. > > 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. > ___ 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] Would you be concerned if the manufacturer does not have an uncertainty budget, so can't provide uncertainties in a calibration?
On 19 April 2018 at 16:42, wrote: > -a calibration certificate without uncertainsties is totally useless. in > is not even a calibration. > Having bought the meter, it is not so useless if it tells me it is working or not, but I do have some concerns I must admit. > -I have never understood why people are so keen on getting things > calibrated at Keysight. > Well, quite simply there's nobody else I would trust to calibrate much of the Agilent equipment. I did contact one UKAS acredited lab, who quoted to calibrate loads of bits of my equipment, but declined this meter. But when I checked the companies uncertainties, I was totally unimpressed. For example, their uncertainty on capacitance at 1 MHz was well in excess of 0.05%, yet they quoted to calibrate the meter, which has a basic uncertainty of 0.05%. I also found their prices were much higher than Keysight. Most companies are not going to be able to adjust Agilent stuff if it is out of spec anyway, as often the software to make the adjustments is not available. So I'm not convinced there is any half-sensible alternative. 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] Would you be concerned if the manufacturer does not have an uncertainty budget, so can't provide uncertainties in a calibration?
-a calibration certificate without uncertainsties is totally useless. in is not even a calibration. -I have never understood why people are so keen on getting things calibrated at Keysight. > Gesendet: Donnerstag, 19. April 2018 um 14:08 Uhr > Von: "Dr. David Kirkby" > An: "Discussion of precise voltage measurement" > Betreff: [volt-nuts] Would you be concerned if the manufacturer does not have > an uncertainty budget, so can't provide uncertainties in a calibration? > > I have an HP 4339B high resistance meter. It can read up to 1.6 x 10^16 > ohms, with a basic uncertainty of 0.6%. It has a built in voltage source of > up to 1 kV. > > I've contacted Keysight (UK) and asked for calibration cost, with > uncertainties, for this 4339B. However, they have said they can't provide a > calibration with uncertainties, and when I asked why, they have said they > do not have an uncertainty budget available that suites that model. Looking > at the Keysight website, a calibration with uncertainties is available in > the USA, but I guess for whatever reason Keysight UK don't have this > ability on this specific instrument. On other instruments I have sent them, > I have never had this issue. > > I expect if I really wanted to, I could get it shipped to the USA and > calibrated there, but I can't justify the costs that would be incurred if > it was shipped to the USA and back. > > From a practical perspective, I don't really need the uncertainties - it > was more for interest sake. I also have a reasonable degree of confidence > that as a reputable company, Keysight would not calibrate an instrument > unless they were confident they could determine if it is in or out of > specification. > > The 4339B is a pretty obscure unit, requiring resistors up to 10^11 ohms to > calibrate it. > > I'm sending this to Keysight with a blank EEPROM, so there will be no > calibration data whatsoever in the instrument. Hopefully that means > everything will be set right, and so likely to stay in specification longer > than it might otherwise do so. There are no trimmers in the 4339B - all > calibration is via the EEPROM. A 3458A is used for calibration of the > voltage source. I'm confidence the voltages will be measured accurately > enough, but a bit less confident about the values of the resistors used for > calibration. > > Dave > > 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.
[volt-nuts] Would you be concerned if the manufacturer does not have an uncertainty budget, so can't provide uncertainties in a calibration?
I have an HP 4339B high resistance meter. It can read up to 1.6 x 10^16 ohms, with a basic uncertainty of 0.6%. It has a built in voltage source of up to 1 kV. I've contacted Keysight (UK) and asked for calibration cost, with uncertainties, for this 4339B. However, they have said they can't provide a calibration with uncertainties, and when I asked why, they have said they do not have an uncertainty budget available that suites that model. Looking at the Keysight website, a calibration with uncertainties is available in the USA, but I guess for whatever reason Keysight UK don't have this ability on this specific instrument. On other instruments I have sent them, I have never had this issue. I expect if I really wanted to, I could get it shipped to the USA and calibrated there, but I can't justify the costs that would be incurred if it was shipped to the USA and back. >From a practical perspective, I don't really need the uncertainties - it was more for interest sake. I also have a reasonable degree of confidence that as a reputable company, Keysight would not calibrate an instrument unless they were confident they could determine if it is in or out of specification. The 4339B is a pretty obscure unit, requiring resistors up to 10^11 ohms to calibrate it. I'm sending this to Keysight with a blank EEPROM, so there will be no calibration data whatsoever in the instrument. Hopefully that means everything will be set right, and so likely to stay in specification longer than it might otherwise do so. There are no trimmers in the 4339B - all calibration is via the EEPROM. A 3458A is used for calibration of the voltage source. I'm confidence the voltages will be measured accurately enough, but a bit less confident about the values of the resistors used for calibration. Dave 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.