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DMMCheck Plus Multimeter Reference(and other References) - Experiences..
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tomud:

--- Quote from: Fungus on July 06, 2023, 05:09:12 pm ---
--- Quote from: tomud on July 05, 2023, 09:15:18 pm ---... the multimeter did not require calibration (saving calibration data in the eeprom memory).

--- End quote ---

Around here that would be called "adjustment".

"Calibration" - measuring reference values and producing a report.

"Adjustment" - modifying the device to improve the accuracy of the displayed values.

--- End quote ---

It's not like we call something a given procedure in our own way. It's about what nomenclature is used officially in different countries because unfortunately I don't know.

For example, in Poland there are two words that translate to the same word calibration in English ("wzorcowanie", "kalibracja")

The concept of calibration ("kalibracja"), for example in Poland, means setting the multimeter, if possible, that is, saving new correction data to the device, and if the equipment does not have such a possibility, providing a comparison table with the reference device. This is usually a much cheaper service that I personally use on hobby equipment. For example, the cost of such a service at the authorized distributor of Brymen in Poland (Biall company - have their own accredited laboratory) - i.e. calibration consisting in saving calibration data to the eeprom memory of the multimeter is about 45 euros + VAT.

There is also such a service performed in accordance with the ISO 17025 (PN-EN ISO/IEC 17025) standard, it costs more. This is called calibration ("wzorcowaniem" - written in Polish) by issuing a  "certyfikat wzorcowania" (written in Polish). Translating into English and German (but I don't know if it's a correct translation): "calibration certificate", "Kalibrierschein"... Such calibrations must, for example, be performed by ISO-certified companies.

Therefore, when writing about calibration here, there may be some misunderstandings due to language differences. So if we are talking about some documents issued by accredited laboratories, it is worth mentioning whether they are in accordance with ISO 17025 or is it just a simpler service of setting / comparing the multimeter with the reference.

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Coming back to cheap measuring equipment. It's ok, you can buy one (I recently bought such inventions as Aneng A3008 and A3009 - but I will use them more as an indicator of whether there is voltage). However, keep in mind that this accuracy may change over time. Similarly, in the case of such multimeters, quality control is practically non-existent, so here too there is a chance that we will receive a new multimeter that, due to some production problems, does not meet the expected parameters. Such multimeters also have other shortcomings. For example, the mentioned Aneng AN870, despite good parameters, has "shallow" sockets. So better cables, e.g. Brymen/Fluke, etc., do not fit it.

J-R:
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

So probably best to not get too bent out of shape on it.
I personally try to stick with the terms the manual states when discussing that product or repairs, just to be consistent.
But otherwise I'm happy to explicitly state such things as calibration/adjustment/data or etc. just to be clear.

With that in mind, my understanding of the DMMCheck Plus "re-calibration" procedure is: an adjustment of the voltage reference to be as spot-on as possible; a small drop of adhesive is applied to the trimmer pot; gather measurements of all references/standards; data printed.  I have never seen the "as-received" calibration data for the voltage reference but I am pretty sure they do perform that and perhaps it is available upon request.

The "recalibration" of the DC voltage references from VoltageStandard.com is also the same.  All the references are tweaked to be as close to the desired value as possible before being sent back to the customer.
mendip_discovery:
Things like this are handy as a check, much like if you use a weighing scale to measure products all the time it's handy to have a calibration weight to check it monthly/weekly etc. Engineers keep gauge blocks handy as a way of checking tools.

I would be happy to use a unit like that to check a home multimeter of 5.5 digits or less. 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.

There is nothing worse than having 2 meters disagree on a measurement to the point where it's hard to determine if it's the thing you are measuring or the kit you are using. Having a sanity check comes in handy then.

Cheap vs Expensive, my experience has been expensive 1 out of 10 might have an issue or two, but a cheap meter 1 out of 10 might actually be rather good. YMMV. As I noted the other day the RS-14 is rather crappy when its battery starts to get low, even though it doesn't tell the user.
bdunham7:

--- Quote from: J-R on July 07, 2023, 08:19:40 am ---The "recalibration" of the DC voltage references from VoltageStandard.com is also the same.  All the references are tweaked to be as close to the desired value as possible before being sent back to the customer.

--- End quote ---

FWIW, Doug puts the as-received value on the certificate as well.
Martin72:

--- Quote from: Martin72 on July 04, 2023, 06:49:45 pm ---Should arrive this week.

--- End quote ---

Has arrived... 8)

Tests will follow in the next days, with my brymen BM869s, East Tester ET4410 LCR Bridge and...
..Two scopes, a 8bit and a 12 bit from siglent(SDS1104X-E and SDS2504X HD which is known for it´s accuracy)
Could be interesting..
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