DIY 10k/10V calibration help request - London/Bay area - Page 1
Forum section: electronics / general

author: Hydron
author_rank: Super Contributor
timestamp: August 31, 2025, 11:30:24 pm
content: So I've just gone and got myself a R6581T, which brings some calibration questions along with the extra digits...The unit I got has an 18 year old calibration, and with the best of my other meters (DMM6500) is sitting at about 4.5 years since last cal and only 6.5 digits, it's difficult to verify much about the new meter other than range transfer accuracy. Getting a professional calibration will probably cost about as much as I paid for the Advantest meter in the first place.What I do have is a well-aged LTZ1000A reference I got from Lee Essen, and a 9k hermetic fluke WW resistor (to which I've added a copper padding resistor to reduce it's initial -1.5ppm/C tempco to about -0.1ppm/C) which could potentially be used as transfer standards for an artifact calibration if anyone is willing and able to measure them well enough to be useful. I live in London but will be heading off tomorrow to Sunnyvale for a couple weeks, so thought I'd ask incase someone is in the bay area and willing to help (or is near enough London for when I'm back home, obviously that would be more convenient especially as the Vref could be carried while hot). If anyone is able to help then it would be much appreciated (DM or post here I guess?)!Futher efforts will probably be trying to figure out how to do the linearity adjustment on the R6581T - it seems that the best way is with a stack of 3458As or possibly a very well adjusted Fluke 720A, which I sadly do not have! I do have a RV722 KVD on it's way, and am thinking of building a AD5791 board, either of which might work as a linearity transfer standard, or at a pinch I could try and do some measure-and-add on the hermetic WW resistor string I salvaged from a Fluke 335D (this is potentially a source of resistors for a better 10k standard too, though I'm reluctant to mess with it's beautiful TC matched resistors!). Any suggestions on this would also be greatly appreciated.

author: Dr. Frank
author_rank: Super Contributor
timestamp: September 01, 2025, 08:18:13 am
content: Hello,as you're now outside of the EU, heavy tariffs will apply, and a very unsafe and longish transport, therefore it's not feasible that I would offer you to fully calibrate your DMM here in Germany.Aren't there any other volt-nuts in UK, who have a complete set of calibration instruments?What about Ian Scott Johnston, he owns a calibrated 3458A, but probably he lacks the necessary stimuli (calibrators)Frank

author: Hydron
author_rank: Super Contributor
timestamp: September 01, 2025, 08:56:20 am
content: Yep the "Brexit dividend" strikes again- that stupidity already cost me a bunch extra when receiving the R6581T. Thanks for the thought though!There is also a forum member in Portugal who may be able to help with the resistance cal (according to a post last year) but again Brexit. At least with a resistance standard it can probably be sent around in a small box as a "gift".If all else fails there's always a chance that I might end up in .de for work (likely Stuttgart) or even a holiday, but it is a big place, though with what seems to be good scattering of voltnuts.I will ping Ian Scott Jonston on the off chance he is willing - a calibrated 3458A, a decent KVD and a decent reference will probably be enough for the R6581T linearity tweaking (or possibly even a popcorn-noise free PVDSmini might do it - it looks like you just need a stable stimulus and very low INL reference meter). I strongly suspect he is in Scotland though, so even if possible would have to be as part of some other trip (train fare to Scotland is normally about as much as an airfare to Germany).

author: perdrix
author_rank: Frequent Contributor
timestamp: September 01, 2025, 10:10:27 am
content: I have a Datron 4808 which agrees with my 3458A which was calibrated against a friends 3458A about two days after he got it back from a Keysight calibration.It's a while since I last used it tho' ...I'm in Warwickshire (Pillerton Priors).David

author: Hydron
author_rank: Super Contributor
timestamp: September 01, 2025, 12:43:51 pm
content: Thanks all,It's sounding like there are a couple of options somewhat reachable from London (though closer would always be better - I think I will need to hire a car for a day), at least for voltage measurements. I've got my fluke resistor with me incase there's someone in the bay area that pops up that could measure it, but otherwise will pick this back up when I'm back. The resistor (or an improved standard if I make one) at least should be relatively easy to ship to someone to measure. Much appreciate the responses

author: RandallMcRee
author_rank: Frequent Contributor
timestamp: September 01, 2025, 02:37:08 pm
content: Hydron,I'm near enough to the Bay Area to measure your Fluke, perhaps.But, of course, I have an informal set of standards, all somewhat like what you are planning, I guess.Let me know if you would like to pursue further and we can meetup while you are in Sunnyvale. I'm in Davis CA 95616.Keithley 2002, cal 2020. R6581T cal via the K2002 in 2020, various 10K standards.Thanks,Randall