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, <pa4tim@gmail.com> 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: acbern@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" <dgminala@mediacombb.net> >> An: "Discussion of precise voltage measurement" <volt-nuts@febo.com> >> Betreff: Re: [volt-nuts] AC calibration >> >> Adrian, >> Do you have a link or title for the NIST paper that you mentioned? >> >> Dave M >> >> >> acbern@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" <dgminala@mediacombb.net> >>>> An: "Discussion of precise voltage measurement" <volt-nuts@febo.com> >>>> 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 >>>> >>>> >>>> pa4tim@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 the people, there is liberty -- Thomas Jefferson >> >> >> Dave M >> >> _______________________________________________ >> 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 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.