Re: [volt-nuts] AC calibration
Fred, The 3458A is 8.5 digits, which puts it into the standards category. They are used as lab standards in many, many labs. 73, Steve WB0DBS > On Aug 27, 2014, at 12:08 AM, wrote: > > Thanks, I did not new NIST has so much interesting information on their site. > > > > > I read the following on their site : > > "multirange instruments with up to eight decimal digits of adjustability, are > not considered by NIST to be standards " > > > > > Does that mean a HP3458 ? Fluke in the Netherlands used a HP-3458 and a 732 > to calibrate the Fluke 5101 that I'm working on at this moment (it failed > calibration due to some hardware faults) > > > > > Everybody thanks for the information. Turns out, a friend has a GR 1455AH for > me, that is some kind a AC KV divider. > > I will test if the output of my HP 3400 is usable to connect a DMM. I have > one I restored a few years ago. Besides that someone mentioned to look at the > LT-1088. > > > But that has to wait until I have some more time. I only repaired > calibration, percission gear and RF stuff for my hobby, but, not planned, I > started to do this on a commercial base too. See my (non commercial) site > about my collection calibration and other gear and projects www.pa4tim.nl . > > Today the 5101 goes back to the custommer but he brings 2 other instruments > in need of some TLC and a precheck before they are shipped to Fluke for > calibration. And yesterday an other company asked if I want/can repair a G&M > safety tester (a sort of megger on steroids) that died during calibration. > > > Fred > > > > Verzonden met Windows Mail > > > > > > Van: acb...@gmx.de > Verzonden: dinsdag 26 augustus 2014 18:56 > Aan: volt-nuts > > > > > > Dave, > > the title is: > Thermal Voltage Converters and Comparator for Very Accurate AC Voltage > Measurements > by E.S.Williams. > > Adrian > > >> Gesendet: Montag, 25. August 2014 um 19:32 Uhr >> Von: "Dave M" >> An: "Discussion of precise voltage measurement" >> Betreff: Re: [volt-nuts] AC calibration >> >> Adrian, >> Do you have a link or title for the NIST paper that you mentioned? >> >> Dave M >> >> >> acb...@gmx.de wrote: >>> fred, >>> generally you raise a good point, I had the same issue of calibrating >>> an ac voltage to a high level of accuracy. you need this e.g. to >>> validate the self.cal of a 3458a or other precison stuff like the >>> 8506a0. >>> >>> what i would recommend to do if you want to keep costs down is: >>> in a nutshell, get a thermal converter in the lowest range you need >>> and a second one on range above. build a set of resistor range >>> extenders (rf type with appropriate connectors and housings) to >>> expand the range to where you need to be max. get one of the thermal >>> converter calibrated (the higher one usually, and you need to havr >>> good cal lab, should be <10ppm accuracy) and use it to calibrate the >>> rest. generally, up to 20khz, the accuracy is some 20 ppm anyway for >>> thermal converters! at higher frequencies, due to reflections and >>> stray capacitance/inductance influences, the accuracy decreases. the >>> resistor range extenders though, if build up correctly, only have a >>> few ppm impact (there is a paper from nist on that, but this is only >>> typical). you can calibrate all converters to the one you got >>> externally calibrated. do some research in the web, when you do the >>> calibration, you need to determine the so-called constant N. then do >>> an ac, dc+, ac, dc-, ac measurement between the the two and establish >>> the deviation, also establish the error propagation. the end result >>> will be a set of highly precise (low inaccuracies9 thermal converters >>> good enough to calibrate a 3458a an better devices. if you want to >>> spend the money, you could also buy a set of converters/range >>> resistors (with/without a 540), that typically is a few k altogether, >>> while a single device sometimes is available for below 100 bucks. you >>> need to have a stable 7.5 digit nanovoltmeter though for the >>> measurements of the tvcs (34420a or 2182 typically ) and precision >>> (stable) dc and ac sources. but in the end, all you need is a single >>> calibrated thermal converter. >>> >>> adrian >>> >>> >>> >>
Re: [volt-nuts] AC calibration
what nist means is that a precision meter is not considered a standard. you always measure against a true standard (732a, esi sr104...). nist does not mean that as part of doing equipment calibration a 3458a cannot be used as aid. also keep in mind nist has a different approach than a cal lab, for obvious reasons. a cal lab would do a transfer measurement using a 3458a and a voltage/current source, sure. there are precision ratio transformers available from various vendors, they can be used for low frequency precision calibrations, up to 20khz only (if anybodys knows one specified above 20khz I am interested to hear). so they will help you only partially in calibrating even a low precision 5101. > Gesendet: Mittwoch, 27. August 2014 um 07:08 Uhr > Von: pa4...@gmail.com > An: volt-nuts > Betreff: Re: [volt-nuts] AC calibration > > Thanks, I did not new NIST has so much interesting information on their site. > > > > > I read the following on their site : > > "multirange instruments with up to eight decimal digits of adjustability, are > not considered by NIST to be standards " > > > > > Does that mean a HP3458 ? Fluke in the Netherlands used a HP-3458 and a 732 > to calibrate the Fluke 5101 that I'm working on at this moment (it failed > calibration due to some hardware faults) > > > > > Everybody thanks for the information. Turns out, a friend has a GR 1455AH for > me, that is some kind a AC KV divider. > > I will test if the output of my HP 3400 is usable to connect a DMM. I have > one I restored a few years ago. Besides that someone mentioned to look at the > LT-1088. > > > But that has to wait until I have some more time. I only repaired > calibration, percission gear and RF stuff for my hobby, but, not planned, I > started to do this on a commercial base too. See my (non commercial) site > about my collection calibration and other gear and projects www.pa4tim.nl . > > Today the 5101 goes back to the custommer but he brings 2 other instruments > in need of some TLC and a precheck before they are shipped to Fluke for > calibration. And yesterday an other company asked if I want/can repair a G&M > safety tester (a sort of megger on steroids) that died during calibration. > > > Fred > > ___ 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] AC calibration
Thanks, I did not new NIST has so much interesting information on their site. I read the following on their site : "multirange instruments with up to eight decimal digits of adjustability, are not considered by NIST to be standards " Does that mean a HP3458 ? Fluke in the Netherlands used a HP-3458 and a 732 to calibrate the Fluke 5101 that I'm working on at this moment (it failed calibration due to some hardware faults) Everybody thanks for the information. Turns out, a friend has a GR 1455AH for me, that is some kind a AC KV divider. I will test if the output of my HP 3400 is usable to connect a DMM. I have one I restored a few years ago. Besides that someone mentioned to look at the LT-1088. But that has to wait until I have some more time. I only repaired calibration, percission gear and RF stuff for my hobby, but, not planned, I started to do this on a commercial base too. See my (non commercial) site about my collection calibration and other gear and projects www.pa4tim.nl . Today the 5101 goes back to the custommer but he brings 2 other instruments in need of some TLC and a precheck before they are shipped to Fluke for calibration. And yesterday an other company asked if I want/can repair a G&M safety tester (a sort of megger on steroids) that died during calibration. Fred Verzonden met Windows Mail Van: acb...@gmx.de Verzonden: dinsdag 26 augustus 2014 18:56 Aan: volt-nuts Dave, the title is: Thermal Voltage Converters and Comparator for Very Accurate AC Voltage Measurements by E.S.Williams. Adrian > Gesendet: Montag, 25. August 2014 um 19:32 Uhr > Von: "Dave M" > An: "Discussion of precise voltage measurement" > Betreff: Re: [volt-nuts] AC calibration > > Adrian, > Do you have a link or title for the NIST paper that you mentioned? > > Dave M > > > acb...@gmx.de wrote: > > fred, > > generally you raise a good point, I had the same issue of calibrating > > an ac voltage to a high level of accuracy. you need this e.g. to > > validate the self.cal of a 3458a or other precison stuff like the > > 8506a0. > > > > what i would recommend to do if you want to keep costs down is: > > in a nutshell, get a thermal converter in the lowest range you need > > and a second one on range above. build a set of resistor range > > extenders (rf type with appropriate connectors and housings) to > > expand the range to where you need to be max. get one of the thermal > > converter calibrated (the higher one usually, and you need to havr > > good cal lab, should be <10ppm accuracy) and use it to calibrate the > > rest. generally, up to 20khz, the accuracy is some 20 ppm anyway for > > thermal converters! at higher frequencies, due to reflections and > > stray capacitance/inductance influences, the accuracy decreases. the > > resistor range extenders though, if build up correctly, only have a > > few ppm impact (there is a paper from nist on that, but this is only > > typical). you can calibrate all converters to the one you got > > externally calibrated. do some research in the web, when you do the > > calibration, you need to determine the so-called constant N. then do > > an ac, dc+, ac, dc-, ac measurement between the the two and establish > > the deviation, also establish the error propagation. the end result > > will be a set of highly precise (low inaccuracies9 thermal converters > > good enough to calibrate a 3458a an better devices. if you want to > > spend the money, you could also buy a set of converters/range > > resistors (with/without a 540), that typically is a few k altogether, > > while a single device sometimes is available for below 100 bucks. you > > need to have a stable 7.5 digit nanovoltmeter though for the > > measurements of the tvcs (34420a or 2182 typically ) and precision > > (stable) dc and ac sources. but in the end, all you need is a single > > calibrated thermal converter. > > > > adrian > > > > > > > >> Gesendet: Montag, 25. August 2014 um 18:38 Uhr > >> Von: "Dave M" > >> An: "Discussion of precise voltage measurement" > >> Betreff: Re: [volt-nuts] AC calibration > >> > >> Well, you sort of answered your own question. The equipment is > >> called a Thermal Transfer Standard, but instead of thermistors, it > >> uses a thermocouple. Look at the manual for the Fluke 540B > >> (http://bama.edebris.com/manuals/fluke/540b/) and you'll see how > >> it's done. Basically, the AC source is input into the transfer > >> standard, and the standard's internal re
Re: [volt-nuts] AC calibration
Great!!@! Many Thanks!! Dave M acb...@gmx.de wrote: Dave, the title is: Thermal Voltage Converters and Comparator for Very Accurate AC Voltage Measurements by E.S.Williams. Adrian Gesendet: Montag, 25. August 2014 um 19:32 Uhr Von: "Dave M" An: "Discussion of precise voltage measurement" Betreff: Re: [volt-nuts] AC calibration Adrian, Do you have a link or title for the NIST paper that you mentioned? ___ 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] AC calibration
In message , acb...@gmx.de writes: Tellurium/copper is used because it machines much better than pure copper, (20% -> 90%) without ruining the conductivity too much. Most other metals which can improve its machinability has big negative impacts on the conductivity of copper. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ 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] AC calibration
Dave, the title is: Thermal Voltage Converters and Comparator for Very Accurate AC Voltage Measurements by E.S.Williams. Adrian > Gesendet: Montag, 25. August 2014 um 19:32 Uhr > Von: "Dave M" > An: "Discussion of precise voltage measurement" > Betreff: Re: [volt-nuts] AC calibration > > Adrian, > Do you have a link or title for the NIST paper that you mentioned? > > Dave M > > > acb...@gmx.de wrote: > > fred, > > generally you raise a good point, I had the same issue of calibrating > > an ac voltage to a high level of accuracy. you need this e.g. to > > validate the self.cal of a 3458a or other precison stuff like the > > 8506a0. > > > > what i would recommend to do if you want to keep costs down is: > > in a nutshell, get a thermal converter in the lowest range you need > > and a second one on range above. build a set of resistor range > > extenders (rf type with appropriate connectors and housings) to > > expand the range to where you need to be max. get one of the thermal > > converter calibrated (the higher one usually, and you need to havr > > good cal lab, should be <10ppm accuracy) and use it to calibrate the > > rest. generally, up to 20khz, the accuracy is some 20 ppm anyway for > > thermal converters! at higher frequencies, due to reflections and > > stray capacitance/inductance influences, the accuracy decreases. the > > resistor range extenders though, if build up correctly, only have a > > few ppm impact (there is a paper from nist on that, but this is only > > typical). you can calibrate all converters to the one you got > > externally calibrated. do some research in the web, when you do the > > calibration, you need to determine the so-called constant N. then do > > an ac, dc+, ac, dc-, ac measurement between the the two and establish > > the deviation, also establish the error propagation. the end result > > will be a set of highly precise (low inaccuracies9 thermal converters > > good enough to calibrate a 3458a an better devices. if you want to > > spend the money, you could also buy a set of converters/range > > resistors (with/without a 540), that typically is a few k altogether, > > while a single device sometimes is available for below 100 bucks. you > > need to have a stable 7.5 digit nanovoltmeter though for the > > measurements of the tvcs (34420a or 2182 typically ) and precision > > (stable) dc and ac sources. but in the end, all you need is a single > > calibrated thermal converter. > > > > adrian > > > > > > > >> Gesendet: Montag, 25. August 2014 um 18:38 Uhr > >> Von: "Dave M" > >> An: "Discussion of precise voltage measurement" > >> Betreff: Re: [volt-nuts] AC calibration > >> > >> Well, you sort of answered your own question. The equipment is > >> called a Thermal Transfer Standard, but instead of thermistors, it > >> uses a thermocouple. Look at the manual for the Fluke 540B > >> (http://bama.edebris.com/manuals/fluke/540b/) and you'll see how > >> it's done. Basically, the AC source is input into the transfer > >> standard, and the standard's internal reference voltage is adjusted > >> for a null on the galvanometer. Leaving the reference voltage > >> setting alone, a DC voltage is input into the unit, and the DC > >> source is adjusted for a null on the galvanometer. At that point, > >> the AC voltage source is equal to that of the DC voltage source. > >> > >> Ther are thermocouple-type thermal converters used for RF voltage > >> measurements with the transfer standard. They aren't cheap, and you > >> have to have a converter for each range of voltages that you need to > >> measure. The thermal converters used with this type of transfer > >> standard isn't great (50 MHz or so typical), but their accuracy far > >> surpasses that of the thermistor type sensors. > >> > >> There are other brands and models of thermal transfer standards, but > >> I have a Fluke model 540 and a few thermal converters. That's why I > >> referred you to the manual for it. > >> > >> Cheers, > >> Dave M > >> > >> > >> pa4...@gmail.com wrote: > >>> Is there a way to link an AC voltage to a DC source for compare. I > >>> can check my calibrators (like a Fluke 332, 760 , 731 and a Philips) > >>> against standardcells. But for AC I can not do that. I have two > >>> AC+DC TRMS 7,5 digit
Re: [volt-nuts] AC calibration
There is one more thing that enters into this discussion and that is "reversal errors" on the DC. The complicates the transfer somewhat. AC is always going "+" and "-". DC is in one direction so you have to then reverse the voltage to the Thermal Transfer Standard and then take the average of the two readings. That is why there is a "Reversal" switch on the 540B. When you are using a fixed voltage High Frequency Thermal Converter you need an external DC reversal switch in addition to other equipment. You also need an AC/DC transfer switch so that you don't have to disconnect the AC source and then hook up the DC source manually. See the 540B again. All Thermal Transfer Standards have some "reversal" error. This is controlled by the internal construction of the unit and exactly where the glass isolation bead is located on the heating element. The thermocouple converter used in the 540B is selected to have a very low reversal error, but always will have some error. The error is fixed so you can approximate a DC measurement once you have characterized the particular converter. I can't remember now but I think there can be up to around .05% reversal errors on some converters, while the ones selected for the 540B are under .01%. Read the FLUKE "Calibration: Philosophy in Practice" for further information. Bill - Original Message - From: "Dave M" To: "Discussion of precise voltage measurement" Sent: Monday, August 25, 2014 11:38 AM Subject: Re: [volt-nuts] AC calibration > Well, you sort of answered your own question. The equipment is called a > Thermal Transfer Standard, but instead of thermistors, it uses a > thermocouple. Look at the manual for the Fluke 540B > (http://bama.edebris.com/manuals/fluke/540b/) and you'll see how it's done. > Basically, the AC source is input into the transfer standard, and the > standard's internal reference voltage is adjusted for a null on the > galvanometer. Leaving the reference voltage setting alone, a DC voltage is > input into the unit, and the DC source is adjusted for a null on the > galvanometer. At that point, the AC voltage source is equal to that of the > DC voltage source. > > Ther are thermocouple-type thermal converters used for RF voltage > measurements with the transfer standard. They aren't cheap, and you have to > have a converter for each range of voltages that you need to measure. The > thermal converters used with this type of transfer standard isn't great (50 > MHz or so typical), but their accuracy far surpasses that of the thermistor > type sensors. > > There are other brands and models of thermal transfer standards, but I have > a Fluke model 540 and a few thermal converters. That's why I referred you > to the manual for it. > > Cheers, > Dave M > > > pa4...@gmail.com wrote: > > Is there a way to link an AC voltage to a DC source for compare. I > > can check my calibrators (like a Fluke 332, 760 , 731 and a Philips) > > against standardcells. But for AC I can not do that. I have two AC+DC > > TRMS 7,5 digit meters but the last calibration was 2 years ago. > > > > My idea is in theory simple. It is based on the thermal converters > > used in RF powermeters. Two resistors, two high resolution > > temperature meters. AC on the first en DC on the second. If both are > > the same temperature the AC voltage is the same as the DC voltage. > > But I'm sure some people here have done this in the past. I would > > like to use it for 50 to 100 kHz (or less) and something like for 1V, > > 10V and 100V (and use several resistors/heaters.) > > > > Or mabey there is an other way to convert AC (for RF it can be done > > with lightbubs but I never tryed that) I do not mind if it is slow > > etc, I like this sort of experiments. You can learn a lot from it. > > > > Fred, pa4tim > > > ___ > 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] AC calibration
Look up the phrase "AC thermal transfer standard". Using a heater/thermocouple element in a vacuum is the tried and true way of linking an AC voltage to a DC reference. -Chuck Harris OBTW, trimming your quoted posts is considered friendly. pa4...@gmail.com wrote: Is there a way to link an AC voltage to a DC source for compare. I can check my calibrators (like a Fluke 332, 760 , 731 and a Philips) against standardcells. But for AC I can not do that. I have two AC+DC TRMS 7,5 digit meters but the last calibration was 2 years ago. My idea is in theory simple. It is based on the thermal converters used in RF powermeters. Two resistors, two high resolution temperature meters. AC on the first en DC on the second. If both are the same temperature the AC voltage is the same as the DC voltage. But I'm sure some people here have done this in the past. I would like to use it for 50 to 100 kHz (or less) and something like for 1V, 10V and 100V (and use several resistors/heaters.) Or mabey there is an other way to convert AC (for RF it can be done with lightbubs but I never tryed that) I do not mind if it is slow etc, I like this sort of experiments. You can learn a lot from it. Fred, pa4tim ___ 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] AC calibration
Adrian, Do you have a link or title for the NIST paper that you mentioned? Dave M acb...@gmx.de wrote: fred, generally you raise a good point, I had the same issue of calibrating an ac voltage to a high level of accuracy. you need this e.g. to validate the self.cal of a 3458a or other precison stuff like the 8506a0. what i would recommend to do if you want to keep costs down is: in a nutshell, get a thermal converter in the lowest range you need and a second one on range above. build a set of resistor range extenders (rf type with appropriate connectors and housings) to expand the range to where you need to be max. get one of the thermal converter calibrated (the higher one usually, and you need to havr good cal lab, should be <10ppm accuracy) and use it to calibrate the rest. generally, up to 20khz, the accuracy is some 20 ppm anyway for thermal converters! at higher frequencies, due to reflections and stray capacitance/inductance influences, the accuracy decreases. the resistor range extenders though, if build up correctly, only have a few ppm impact (there is a paper from nist on that, but this is only typical). you can calibrate all converters to the one you got externally calibrated. do some research in the web, when you do the calibration, you need to determine the so-called constant N. then do an ac, dc+, ac, dc-, ac measurement between the the two and establish the deviation, also establish the error propagation. the end result will be a set of highly precise (low inaccuracies9 thermal converters good enough to calibrate a 3458a an better devices. if you want to spend the money, you could also buy a set of converters/range resistors (with/without a 540), that typically is a few k altogether, while a single device sometimes is available for below 100 bucks. you need to have a stable 7.5 digit nanovoltmeter though for the measurements of the tvcs (34420a or 2182 typically ) and precision (stable) dc and ac sources. but in the end, all you need is a single calibrated thermal converter. adrian Gesendet: Montag, 25. August 2014 um 18:38 Uhr Von: "Dave M" An: "Discussion of precise voltage measurement" Betreff: Re: [volt-nuts] AC calibration Well, you sort of answered your own question. The equipment is called a Thermal Transfer Standard, but instead of thermistors, it uses a thermocouple. Look at the manual for the Fluke 540B (http://bama.edebris.com/manuals/fluke/540b/) and you'll see how it's done. Basically, the AC source is input into the transfer standard, and the standard's internal reference voltage is adjusted for a null on the galvanometer. Leaving the reference voltage setting alone, a DC voltage is input into the unit, and the DC source is adjusted for a null on the galvanometer. At that point, the AC voltage source is equal to that of the DC voltage source. Ther are thermocouple-type thermal converters used for RF voltage measurements with the transfer standard. They aren't cheap, and you have to have a converter for each range of voltages that you need to measure. The thermal converters used with this type of transfer standard isn't great (50 MHz or so typical), but their accuracy far surpasses that of the thermistor type sensors. There are other brands and models of thermal transfer standards, but I have a Fluke model 540 and a few thermal converters. That's why I referred you to the manual for it. Cheers, Dave M pa4...@gmail.com wrote: Is there a way to link an AC voltage to a DC source for compare. I can check my calibrators (like a Fluke 332, 760 , 731 and a Philips) against standardcells. But for AC I can not do that. I have two AC+DC TRMS 7,5 digit meters but the last calibration was 2 years ago. My idea is in theory simple. It is based on the thermal converters used in RF powermeters. Two resistors, two high resolution temperature meters. AC on the first en DC on the second. If both are the same temperature the AC voltage is the same as the DC voltage. But I'm sure some people here have done this in the past. I would like to use it for 50 to 100 kHz (or less) and something like for 1V, 10V and 100V (and use several resistors/heaters.) Or mabey there is an other way to convert AC (for RF it can be done with lightbubs but I never tryed that) I do not mind if it is slow etc, I like this sort of experiments. You can learn a lot from it. Fred, pa4tim ___ 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. When the people fear the government, there is tyranny. When the government fears
Re: [volt-nuts] AC calibration
fred, generally you raise a good point, I had the same issue of calibrating an ac voltage to a high level of accuracy. you need this e.g. to validate the self.cal of a 3458a or other precison stuff like the 8506a0. what i would recommend to do if you want to keep costs down is: in a nutshell, get a thermal converter in the lowest range you need and a second one on range above. build a set of resistor range extenders (rf type with appropriate connectors and housings) to expand the range to where you need to be max. get one of the thermal converter calibrated (the higher one usually, and you need to havr good cal lab, should be <10ppm accuracy) and use it to calibrate the rest. generally, up to 20khz, the accuracy is some 20 ppm anyway for thermal converters! at higher frequencies, due to reflections and stray capacitance/inductance influences, the accuracy decreases. the resistor range extenders though, if build up correctly, only have a few ppm impact (there is a paper from nist on that, but this is only typical). you can calibrate all converters to the one you got externally calibrated. do some research in the web, when you do the calibration, you need to determine the so-called constant N. then do an ac, dc+, ac, dc-, ac measurement between the the two and establish the deviation, also establish the error propagation. the end result will be a set of highly precise (low inaccuracies9 thermal converters good enough to calibrate a 3458a an better devices. if you want to spend the money, you could also buy a set of converters/range resistors (with/without a 540), that typically is a few k altogether, while a single device sometimes is available for below 100 bucks. you need to have a stable 7.5 digit nanovoltmeter though for the measurements of the tvcs (34420a or 2182 typically ) and precision (stable) dc and ac sources. but in the end, all you need is a single calibrated thermal converter. adrian > Gesendet: Montag, 25. August 2014 um 18:38 Uhr > Von: "Dave M" > An: "Discussion of precise voltage measurement" > Betreff: Re: [volt-nuts] AC calibration > > Well, you sort of answered your own question. The equipment is called a > Thermal Transfer Standard, but instead of thermistors, it uses a > thermocouple. Look at the manual for the Fluke 540B > (http://bama.edebris.com/manuals/fluke/540b/) and you'll see how it's done. > Basically, the AC source is input into the transfer standard, and the > standard's internal reference voltage is adjusted for a null on the > galvanometer. Leaving the reference voltage setting alone, a DC voltage is > input into the unit, and the DC source is adjusted for a null on the > galvanometer. At that point, the AC voltage source is equal to that of the > DC voltage source. > > Ther are thermocouple-type thermal converters used for RF voltage > measurements with the transfer standard. They aren't cheap, and you have to > have a converter for each range of voltages that you need to measure. The > thermal converters used with this type of transfer standard isn't great (50 > MHz or so typical), but their accuracy far surpasses that of the thermistor > type sensors. > > There are other brands and models of thermal transfer standards, but I have > a Fluke model 540 and a few thermal converters. That's why I referred you > to the manual for it. > > Cheers, > Dave M > > > pa4...@gmail.com wrote: > > Is there a way to link an AC voltage to a DC source for compare. I > > can check my calibrators (like a Fluke 332, 760 , 731 and a Philips) > > against standardcells. But for AC I can not do that. I have two AC+DC > > TRMS 7,5 digit meters but the last calibration was 2 years ago. > > > > My idea is in theory simple. It is based on the thermal converters > > used in RF powermeters. Two resistors, two high resolution > > temperature meters. AC on the first en DC on the second. If both are > > the same temperature the AC voltage is the same as the DC voltage. > > But I'm sure some people here have done this in the past. I would > > like to use it for 50 to 100 kHz (or less) and something like for 1V, > > 10V and 100V (and use several resistors/heaters.) > > > > Or mabey there is an other way to convert AC (for RF it can be done > > with lightbubs but I never tryed that) I do not mind if it is slow > > etc, I like this sort of experiments. You can learn a lot from it. > > > > Fred, pa4tim > > > ___ > 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] AC calibration
Well, you sort of answered your own question. The equipment is called a Thermal Transfer Standard, but instead of thermistors, it uses a thermocouple. Look at the manual for the Fluke 540B (http://bama.edebris.com/manuals/fluke/540b/) and you'll see how it's done. Basically, the AC source is input into the transfer standard, and the standard's internal reference voltage is adjusted for a null on the galvanometer. Leaving the reference voltage setting alone, a DC voltage is input into the unit, and the DC source is adjusted for a null on the galvanometer. At that point, the AC voltage source is equal to that of the DC voltage source. Ther are thermocouple-type thermal converters used for RF voltage measurements with the transfer standard. They aren't cheap, and you have to have a converter for each range of voltages that you need to measure. The thermal converters used with this type of transfer standard isn't great (50 MHz or so typical), but their accuracy far surpasses that of the thermistor type sensors. There are other brands and models of thermal transfer standards, but I have a Fluke model 540 and a few thermal converters. That's why I referred you to the manual for it. Cheers, Dave M pa4...@gmail.com wrote: Is there a way to link an AC voltage to a DC source for compare. I can check my calibrators (like a Fluke 332, 760 , 731 and a Philips) against standardcells. But for AC I can not do that. I have two AC+DC TRMS 7,5 digit meters but the last calibration was 2 years ago. My idea is in theory simple. It is based on the thermal converters used in RF powermeters. Two resistors, two high resolution temperature meters. AC on the first en DC on the second. If both are the same temperature the AC voltage is the same as the DC voltage. But I'm sure some people here have done this in the past. I would like to use it for 50 to 100 kHz (or less) and something like for 1V, 10V and 100V (and use several resistors/heaters.) Or mabey there is an other way to convert AC (for RF it can be done with lightbubs but I never tryed that) I do not mind if it is slow etc, I like this sort of experiments. You can learn a lot from it. Fred, pa4tim ___ 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] AC calibration
Is there a way to link an AC voltage to a DC source for compare. I can check my calibrators (like a Fluke 332, 760 , 731 and a Philips) against standardcells. But for AC I can not do that. I have two AC+DC TRMS 7,5 digit meters but the last calibration was 2 years ago. My idea is in theory simple. It is based on the thermal converters used in RF powermeters. Two resistors, two high resolution temperature meters. AC on the first en DC on the second. If both are the same temperature the AC voltage is the same as the DC voltage. But I'm sure some people here have done this in the past. I would like to use it for 50 to 100 kHz (or less) and something like for 1V, 10V and 100V (and use several resistors/heaters.) Or mabey there is an other way to convert AC (for RF it can be done with lightbubs but I never tryed that) I do not mind if it is slow etc, I like this sort of experiments. You can learn a lot from it. Fred, pa4tim Verzonden met Windows Mail Van: Bill Gold Verzonden: maandag 25 augustus 2014 15:40 Aan: volt-nuts Randy: Sorry my fault. You have to use the "RMATH" command to get the various values stored in the registers. See the "RMATH" command in the User's Guide for a list of what registers you can read. I sure haven't found any other guides other than the 4 manuals. User's Guide, Quick Reference Guide, Calibration Manual, and Assembly Level Repair. It is just a matter of reading the guides and trying to remember what commands are available. It took me a lot of time to figure out what commands I use now. I am sure I am missing other commands that might be useful. Bill - Original Message - From: "Randy Evans" To: "Discussion of precise voltage measurement" Sent: Sunday, August 24, 2014 6:04 PM Subject: Re: [volt-nuts] 732A and Prologix received > Bill, > > I am trying to figure out the MATH function without much success. I input > the sequence you said (I looked up the instructions to understand what you > did - seems logical), BLUE DEFKEY BLUE F1 MATH 14;NRDGS 40;TRIG 4;TRIG; and > it shows up on the display when I input BLUE F1. I hit ENTER and it takes > the 40 measurements and the MATH symbol shows on the display during the > measurements. After the SMPL symbol no longer blinks I hit MATH 2 and I > get a MATH ERR symbol on the display. I tried it a couple of times and the > same result so I am doing something wrong. Is there a better source for > explaining how to do front panel masurements than the User Guide, which > seems oriented at programming automatic rather than manual measurements. > > Randy > > > > On Sun, Aug 24, 2014 at 4:46 PM, Bill Gold wrote: > > > Randy: > > > > The MATH function is accessible from the keypad. I don't have an IEEE > > interface right now that works. You can also program the numeric keypad > > keys to have preprogrammed functions. DEFKEY > > > > I have made my own "low thermal" measurement leads from Pomona #4892 > > banana plugs and Belden #9272 wire. Why 9272, because it was handy at the > > time. It is tin plated copper, shielded twisted pair 20 ga. I have plans > > to do custom cables with 16 ga. bare copper wire that I will twist and then > > put a braided shield over it. I simply cannot find what I want so I will > > build my own cable. I have done something like this before and it worked > > fine. When I get a "round toit". > > > > I have 6 ea. Pomona 1756-48 spade lug low thermal leads that I have > > used > > in the past to verify my homemade "low thermal" leads as described above. > > Frankly I cannot see any difference between using the 1756 cables and my > > homemade cables once I give them a few minutes for the thermals to go away. > > As far as I can tell and measure the differences, if any, are below 0.1 ppm > > at 10 volts. > > > > Since the 10 volt, 1.0 volt and 1.018 volt outputs on the 732A are all > > adjustable you may be seeing a misadjusted 1 volt from the 732A. As far as > > the instability of the readings it is hard to determine which is causing > > the > > problem. I have programed (DEFKEY) a numeric keypad key #1 with the > > following code. "MATH 14;NRDGS 40;TRIG 4;TRIG ;" So what this does is > > set > > the MATH to "Statistics" (store high reading/low reading/ and mean of the > > readings) in the registers, the number of readings to "40", the trigger to > > "hold" (which keeps the meter from triggering until I press "ENTER" and > > then > > trigger the sequence of 40 readings when I push the "ENTER" button. You > > can > > do all of this manually from the keypads but since I use this sequence a > > lot > > I have preprogrammed it. This is after I set digits to "8" and PLC to 100. > > Once those 40 readings are finished then you can access the various MATH > > statistic registers, using the menu, by entering "MATH" and then a 2 for > > low, a 4 for mean, and 13 for high. Of course you could do all of this > > through the IE
