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Brymen 869s DC offset issue when reading ACmV
bdunham7:
--- Quote from: Neutrion on January 24, 2022, 08:21:11 pm ---Did by the way anyone tested this scale of the 87V with a DC bias, and for overrange indication?
--- End quote ---
IIRC yes, but it is AC coupled so there are no surprises there and not a memorable event.
You mentioned in another thread that this issue was 'common' and that even many Flukes exhibit it. I can't comment on any that I don't have to test, but I'm not seeing that at all. What might be observed is that some of the Flukes, for example my F116, will appear at first to have an error when you apply a DC bias to an AC signal in the mVAC range. This actually takes effect even at lower signal levels and is not due to overloading. What these meters with DC-coupled mVAC ranges are doing is correctly displaying the TRMS AC+DC value, not just the AC component. That isn't clear just by looking at the meter, so demerits points for that. However, keeping that in mind, I still haven't managed to get any of them to display a 'wrong' reading. It is correct or OL.
J-R:
To clarify, I only tested some of my handheld DMMs and didn't provide the full list of failures. I have a few more from Amprobe, UEi, etc. that I didn't mention.
There are plenty of handheld DMMs that can get away with showing some/most readings. There are also plenty of tricks to work around the "issue".
But I consider it a fail if it can't correctly display all three of the signal properties, AC, DC & frequency. This also goes for bench DMMs that don't support frequency.
I gave the Sanwa a pass but the others get a hard fail for not being able to show the frequency, even despite the fact they can display 100mVAC correctly in VAC mode.
bdunham7:
--- Quote from: J-R on January 24, 2022, 09:54:22 pm ---But I consider it a fail if it can't correctly display all three of the signal properties, AC, DC & frequency. This also goes for bench DMMs that don't support frequency.
I gave the Sanwa a pass but the others get a hard fail for not being able to show the frequency, even despite the fact they can display 100mVAC correctly in VAC mode.
--- End quote ---
I don't see the point of 'failing' a device for lacking a specific feature that it doesn't purport to have.
J-R:
--- Quote from: bdunham7 on January 24, 2022, 10:07:49 pm ---
--- Quote from: J-R on January 24, 2022, 09:54:22 pm ---But I consider it a fail if it can't correctly display all three of the signal properties, AC, DC & frequency. This also goes for bench DMMs that don't support frequency.
I gave the Sanwa a pass but the others get a hard fail for not being able to show the frequency, even despite the fact they can display 100mVAC correctly in VAC mode.
--- End quote ---
I don't see the point of 'failing' a device for lacking a specific feature that it doesn't purport to have.
--- End quote ---
I was primarily referring to the handheld DMMs that DO claim to have that feature. The bench DMMs that can't do frequency I am considering a fail for the OPs original request.
bdunham7:
--- Quote from: J-R on January 24, 2022, 11:21:08 pm ---I was primarily referring to the handheld DMMs that DO claim to have that feature. The bench DMMs that can't do frequency I am considering a fail for the OPs original request.
--- End quote ---
OK. If you take the OP's stated needs to be AC-coupled mVAC, readout in dBm, 20,000 counts or more, frequency readout at ~100mVAC or lower and then you read in handheld and probably CAT-rated, that knocks out a lot of products. If he doesn't need handheld and CAT III/IV ratings, then most modern bench meters will likely work.
The only inexpensive (relatively) meter I can think of that may meet the OP's specific requirements in this case is the manual-ranging BK Precision 391A. All the AC ranges are AC coupled, it has a 200mVAC range, the frequency range stated sensitivity is 50mVrms and it is 20,000 counts.
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