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DMMCheck Plus Multimeter Reference(and other References) - Experiences..
mendip_discovery:
Do some tests, and record the results. Do it again ina few months. Compare it to another TEA victim nearby. If you can find a nice lab that will do calibration for sensible money in the future do it and you can build up some confidence in the unit.
Thanks for sharing the cert btw. I like to see what others do.
tomud:
--- Quote from: mendip_discovery on July 07, 2023, 01:33:36 pm --- It might be a bit of a challenge for a 6.5 or 8.5 as they are much better than the specs of the DMMCheck.
--- End quote ---
6 and 1/2 digits is ok, 8 and 1/2 digits make absolutely no sense. While buying such a multimeter is real, keeping it in good condition, including calibration, is not easy fun. These are high costs, not all laboratories can calibrate such an 8 1/2 multimeter. On the other hand, buying 8 and 1/2 of some old one, which has no known accuracy, does not make any sense. Well, unless I just boast that I have such a multimeter.
In fact, if I wanted to become independent, I'd build my own real calibrator, although it's expensive fun. Right now it's cheaper for me to calibrate my 6 1/2 digit multimeters (non-ISO 17025 certified) - as it's not terribly expensive. However, as standards in my home laboratory, they are sufficient - I absolutely do not need 8 1/2 digits to calibrate a multimeter bought for around 200 euros (6 1/2 is fully sufficient).
Steve77:
--- Quote from: J-R on July 07, 2023, 08:19:40 am ---The International Vocabulary of Metrology (VIM) was first published in 1984 and has had many revisions since. The VIM of course pushes the separate definitions of calibration and adjustment among other specific terms, but it's not a guarantee that everyone just adopts such things immediately. Plenty of older manuals consider calibration to include adjusting the instrument if necessary, and I still see this used in modern times as well: https://www.ianjohnston.com/index.php/onlineshop/handheld-precision-digital-voltage-source-2-mini-detail
J-R: Thank you for mentioning this document. I did a quick Google search and came up with a 2021 version that I will archive. It will be nice to use standard language in procedures and test documents so I can pretend that I know what I am talking about.
--- End quote ---
alm:
--- Quote from: tomud on July 07, 2023, 05:46:48 pm ---6 and 1/2 digits is ok, 8 and 1/2 digits make absolutely no sense. While buying such a multimeter is real, keeping it in good condition, including calibration, is not easy fun. These are high costs, not all laboratories can calibrate such an 8 1/2 multimeter. On the other hand, buying 8 and 1/2 of some old one, which has no known accuracy, does not make any sense. Well, unless I just boast that I have such a multimeter.
--- End quote ---
Adjustment is actually quite straight-forward for a certain popular 8.5 digit meter (3458A), all it requires is a good short, an accurate 10 kOhm resistor and an accurate 10 V source. Costs about €130 here (forum user AP). That's actually much easier than adjusting something like a HP/Agilent 34401A which requires a whole bunch of voltages, currents and resistances to calibrate and adjust it.
Resolution, stability and linearity has value beyond accuracy. For example, you might compare two resistors by putting them in series, putting a voltage across them and then comparing the voltage across the two resistors. If the meter has good short term stability and linearity, you can measure the ratio of the two resistors very accurately without needing any absolute accuracy.
--- Quote from: tomud on July 07, 2023, 05:46:48 pm ---Right now it's cheaper for me to calibrate my 6 1/2 digit multimeters (non-ISO 17025 certified) - as it's not terribly expensive. However, as standards in my home laboratory, they are sufficient - I absolutely do not need 8 1/2 digits to calibrate a multimeter bought for around 200 euros (6 1/2 is fully sufficient).
--- End quote ---
No argument there :)
Martin72:
I have already tried something, the L/C/R section.
The meter was the ET4410 (LCR Bridge).
This is exactly how I imagined it, I now have a reference with which I can compare different devices, this makes things easier in the future.
The next device will be the Brymen 869s, then possibly the Oscilloscope, a Hioki LCR, and so on.
I will always post here.
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