Electronics > Metrology

121GW not passing calibration

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J-R:
I experimented with calibrating the ACV ranges of the 121GW but the documented procedure is blatantly incorrect (even with the 10% offset).  I am trying to track down the correct, full procedure.  I have one Kickstarter 121GW that is not so great at ACV and another newer one that is very good (2021-ish).

mbd16:
Thanks for looking into this! Are you suggesting the calibration procedure in the 121GW documentation is not correct?

My 121GW was purchased September of 2021 from the EEVBlog store for reference.

I think at this point I'm just going to have them label this unit as uncalibrated and not to be used for official testing. We've got plenty of calibrated multimeters in back I can use, and just keep this around for testing simple prototypes. Can always reference it with other calibrated meters every now and then just to see where it's at.

But i'll stay posted and check back here for updates (if any).

Thanks again!


Edit: got the full calibration report back. See attachments below

mendip_discovery:
I would just put a label on that says do not use on AC above 1 kHz

Its a good meter and would be a shame not to use it just because of an edge case that someone might be measuring AC voltage at 5 kHz with a handheld multimeter.

J-R:
The 121GW calibration procedure from the manual is somewhere between incomplete and blatantly incorrect.  It makes no sense to not have this information all these years later after release so it seems clear UEi is playing some games here.

I adjusted/calibrated at various specific frequencies using different methods based on the manual, community information and other info gleaned from a similar DMM sold by UEi.  If you test afterwards at that same frequency, the readings are perfect, but simply select another frequency and they are very far off.

I reached out to the company I purchased the unit from and they said they would contact the manufacturer, but I have not heard anything since.

J-R:
Got my hands on this.  I tried the 5V range and it worked.  Back up your calibration first!

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