Products > Test Equipment
Brymen BM789
2N3055:
--- Quote from: Neutrion on September 24, 2021, 01:17:06 pm ---But than also designing your own thing, and knowing all the guts of it (I suppose you Joe mostly design stuff) makes you to to take different measures than starting to measure around in something which you have not much idea about, maybe not even a schematics is aviable. And there could be also some hazardous failure modes, which in theory should not happen but they do sometimes.
Can any of you also bring the 869 to show 0 Volts with a dc offset? Though there with the dual display less of an issue.
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It is irrelevant if you are designing thing on your own, or you are repairing someone else's design.
If you are repairing something unknown, first order of business is to make it known, at least to the point to be able to understand where are the dangerous parts. Any part of circuit that can become dangerous in any scenario (even the fault far outside normal operating parameters) should be permanently treated as dangerous. Not to protect your meter but your life..
BM869 question I answered 3-4 times already. Yes and no.
Neutrion:
I run through the topic, but only found this. But here you write about incorrect nubers, but not necessarily 0.
--- Quote from: 2N3055 on September 13, 2021, 03:27:40 pm ---
--- Quote from: Neutrion on September 13, 2021, 02:50:47 pm ---
But does the 869 correctly shows "OL" for AC in this scenario? Did you try to switch polarity?
With the 869 it makes sense to have everything on the same switch position, but with the single display if there is no way to show overrange they certainly could put in a separate AC mV position.
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I think we have a language barrier here.
BM869S has 2 different positions for DC and AC mV, but both are nevertheless still DC coupled .
It does show OVL if you apply larger AC voltage. If you combine it with DC, that combined goes over range it also behaves funny.
For instance 1V P-P 400HZ square wave, will show correct 500mV RMS. If I add more than 0.6 V DC to it (offset) it will start showing wrong numbers. Funny enough, I can add -2,3V offset before it starts making problems. So it is not symmetric.
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joeqsmith:
--- Quote from: Neutrion on September 24, 2021, 01:17:06 pm ---But than also designing your own thing, and knowing all the guts of it (I suppose you Joe mostly design stuff) makes you to to take different measures than starting to measure around in something which you have not much idea about, maybe not even a schematics is aviable. And there could be also some hazardous failure modes, which in theory should not happen but they do sometimes.
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Typically when I need to repair something that is new enough that I can't get schematics and it's actually something that is worth the time to attempt to repair, I start by writing down every part number of the ICs and pull the data sheets. Then I start to trace out the design. Most of the time, I have some idea where to look based on the symptoms and so I am only looking at small sections of the design.
Just because schematics are not available for free off the internet doesn't mean they are not available. I have written companies before and have been able to obtain schematics and service manuals.
--- Quote from: Neutrion on September 24, 2021, 01:17:06 pm ---Can any of you also bring the 869 to show 0 Volts with a dc offset? Though there with the dual display less of an issue.
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Does it really matter? I saw it as more a gimmick than anything useful.
Neutrion:
This is a good throughout approach, but often one does not have the time for it, and have to start to measure around to get an idea. Of course it's not ideal.
--- Quote from: joeqsmith on September 24, 2021, 02:16:02 pm ---
--- Quote from: Neutrion on September 24, 2021, 01:17:06 pm ---Can any of you also bring the 869 to show 0 Volts with a dc offset? Though there with the dual display less of an issue.
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Does it really matter? I saw it as more a gimmick than anything useful.
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No, but I am interested. And the 869 is the competitor to the 789 within Brymen. (And actually not much of a competition in this price/quality range anywhere else...)
But generally it matters with the 789 because first I thought, that below a given displayed mV AC level I could feel myself "safe" but it seems that it is not the case.
I don't know how fast it could work in FW but if the meter would only switch internally to DC measurement, it should only check if its above 1 V DC in any any direction, and than it could display OL.
We will see.
joeqsmith:
--- Quote from: Neutrion on September 24, 2021, 02:45:26 pm ---...
But generally it matters with the 789 because first I thought, that below a given displayed mV AC level I could feel myself "safe" but it seems that it is not the case.
...
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Feel Safe? It's rare I work on anything where I'm concerned with safety. In those cases, I never feel safe! :-DD I'm also not playing with mV. :-DD
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