Anyone with multimeter calibration facilities based in UK? - Page 1
Forum section: electronics / testgear

author: giosif
author_rank: Frequent Contributor
timestamp: September 08, 2015, 12:24:40 am
content: Hi,Is there someone UK based (ideally, South East England) who might have the right gear and be willing to help this poor fella with calibrating his meters?He's got 2 DMM's and one bench multimeter that he would like to calibrate but, with a budget as good as non-existent, going the commercial route is not really an option.Of course, he would like to offer something equivalent in exchange, but all he knows is a bit of computing and (Wi-Fi) networking (which, most likely, everyone in here knows already).Thanks!

author: artag
author_rank: Super Contributor
timestamp: September 09, 2015, 09:05:55 pm
content: He's welcome to compare it with my selection of meters (best is probably an HP34401A or a Keithley 2000). I'm in east anglia, between A1 and M1. Deciding which is most correct is probably the tough option.Maybe ask on the volt-nut mailing list for a wiser and better calibrated view ?

author: giosif
author_rank: Frequent Contributor
timestamp: September 10, 2015, 01:00:09 pm
content: Thanks for the offer, artag!However, I already have an idea which of the meters is off and, roughly, with how much.What I'm looking for is something like a multimeter calibrator or equivalent, so I can actually perform the calibration procedure on the meters.I'll try volt-nut and see what luck I have there.Thanks again!

author: Howardlong
author_rank: Super Contributor
timestamp: September 10, 2015, 01:54:19 pm
content: Not sure if it's any good to you I'm in Central London and have the enclosed version of the DMM Checker Plus set of DC/AC voltage/current/resistance standards and a 34401A too.http://www.voltagestandard.com/DMMCheck_Plus.html

author: giosif
author_rank: Frequent Contributor
timestamp: September 10, 2015, 05:27:18 pm
content: Location is fine, but I'm afraid I'm still out of luck with the calibration, as what I need is a device or set of devices capable of providing tusted high resolution & high accuracy voltage, current, and resistance (and, possibly, even capacitance)at specific values.And those specific values are dictated by the multimeter you are trying to calibrate.For instance, for a Fluke 8842A multimeter I have, I'd need the values in the attached picture (and quite possibly some other values).Unless I'm reading the calibration instructions the wrong way...

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: September 10, 2015, 05:34:01 pm
content: Quote from: giosif on September 10, 2015, 05:27:18 pmYou don't necessarily need a precise value, just a stable (ideally adjustable) one and something accurate to measure it with..

author: giosif
author_rank: Frequent Contributor
timestamp: September 10, 2015, 07:12:57 pm
content: I'm not sure I follow: if it's not precisely the value(s) they mention, how would the meter record the drift/offset?

author: Fungus
author_rank: Super Contributor
timestamp: September 10, 2015, 07:26:10 pm
content: Quote from: giosif on September 10, 2015, 07:12:57 pmIt doesn't have to be pretty number like 10.0000V, it can be 7.2165V (or whatever). The only important thing is that it's stable and always outputs that exact same voltage.To calibrate your meter you connect it up and twiddle the knob until it reads "7.2165".

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: September 10, 2015, 07:58:13 pm
content: Quote from: giosif on September 10, 2015, 07:12:57 pmIf it has an auto cal procedure that needs a specific input voltage, use an adjustable voltage source that you can monitor with an accurate DMM - adjust til it's bang on then hit the "calibrate" button

author: Macbeth
author_rank: Super Contributor
timestamp: September 10, 2015, 08:05:58 pm
content: I know what you mean, you want a calibrator like aFluke 5720A. Personally, I think they are just a smidgeon too expensive, even 2nd hand on ebay.There is alsoProject KXwhich looks like an excellent idea, but is not yet available.A more old fashioned and realistically achievable way is to look up Conrads Mini Metrology Lab, then when you find the Kelvin Varley Divider is probably too much work, go for a Hamon Divider with /10 and /100.Of course a decent calibrated 10V ref is a good idea. I've got a couple of LM399's as LTZ1000 territory is too costly. (LM399's and LT1001's etc I got for free from Linear as samples)It becomes a never ending project and beware - volt nuttery is involved.Now the issue is the calibration procedure on your devices. Like you, I have meters that need an exact multiple of 1.9 on all ranges with a limited deviation. Other meters like the Keithley will allow 9-11 volts for it's 10V cal and let you program the actual voltage. This is great as my Chinese ref puts out 10.00275V so I have my 2 Keithleys exact.My other meters are lower spec from 3.5 to 5.5 digit and so I can get away with using my PSU with my Keithley to measure the voltage output and I hit the cal button when I get exactly 190.000mV, 1.90000V, 19.00000 etc.I need higher voltages and an accurate divider to do the rest.Then there is resistance, and AC to deal with...

author: giosif
author_rank: Frequent Contributor
timestamp: September 10, 2015, 08:45:14 pm
content: @Fungus: That procedure would work for some meters, but what I have supports what is called "closed-case calibration" - a.k.a. the auto calibration Mike is referring to and Macbeth describes in more detail.@Mike: True, but that assumes two things: first, you have another accurate DMM and, second, you have a voltage source that can go all the way up to 1,000 V DC !!!@Macbeth: Yes, the calibrator is what I had in mind (or something equivalent per each measurement).Wow. Based on your story, I might be better off starting saving money and going for the commercial calibration option.And interesting aspect about Keithley, as that makes calibration much easier to achieve.