Products > Test Equipment
New EEVblog BM786 Multimeter
bdunham7:
--- Quote from: rsjsouza on January 08, 2022, 04:38:04 pm ---While I agree with the premise, I can't shake the feeling that something is amiss if this should be considered a normal behaviour of the BM78x series. I have been through many multimeters of several brands and the RM102Pro was the only one that gave me random beeps that I can recall. And I have used and tested many crap and excellent models/brands.
--- End quote ---
If you set up a test rig with a capacitor and a bleed resistor well above the continuity threshold, say 10k, and then test continuity with different capacitors and different meters you should find that all of the meters will emit a beep, squeak or chirp if you go above a certain capacitor size. The capacitor size at which you first hear a sound will vary quite a bit from meter to meter. Those meters that respond to the smaller capacitors will also be the ones that catch a short as you scan a probe down a row of connectors. AFAIK, there's no easy way around that tradeoff. One other variable would be the continuity threshold--it would make some difference it were unusually high. The BM786 says "100 to 420ohms".
Edit: There's one more variable--test current--and for the BM786 it is fairly low at ~350uA. That would also make it more sensitive to capacitors.
tautech:
--- Quote from: rsjsouza on January 07, 2022, 11:40:53 pm ---I had this on an ultra-cheap Richmeters RM102Pro (Aneng 113D). It pissed me off.
With Brymen, it might be a random issue, although having a fellow youtuber go through this as well is concerning.
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Why ?
Just like any instrument learn to know what it does under various usage conditions and adapt to it. You can't have super fast continuity and it not also react to probing across a capacitance.
The Kaise moving coil meter I got for my 21st would always display a cap charging and for really stuffed ones display if they were leaking too. Way back in the 70's we used this behavior to good effect before the days of cap testers.
Fungus:
--- Quote from: Meter Deter on January 07, 2022, 07:11:02 pm ---i never had this issue with a Amprobe AM-570 that got stolen.
or my cheap UNI-T UT61E that i replace for this BM786
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Maybe they had slower continuity function.
As others have said, if you probe a discharged capacitor it will appear as a short-circuit for a fraction of a second. That's electronics.
If a meter's continuity test is fast then it will beep. If it's slower, it won't.
nb. It will also depend on the meter's continuity test voltage, the size of the capacitor, the ESR of the capacitor, etc.
OTOH the meter might be defective. Find the minimum resistance it beeps on, eg. with a potentiometer and measure that resistance. Does it match what it says in the manual?
rsjsouza:
--- Quote from: EEVblog on January 09, 2022, 04:03:27 am ---
--- Quote from: rsjsouza on January 08, 2022, 04:38:04 pm ---
--- Quote from: EEVblog on January 08, 2022, 06:32:15 am ---
--- Quote from: rsjsouza on January 07, 2022, 11:40:53 pm ---I had this on an ultra-cheap Richmeters RM102Pro (Aneng 113D). It pissed me off.
With Brymen, it might be a random issue, although having a fellow youtuber go through this as well is concerning. Perhaps it is a variability of part tolerances?
--- End quote ---
The Brymen is a fast responding meter, and there is always variability in the detection threshold between meters. No two model meters will be idential here is you are dealing with capacitive loads.
--- End quote ---
While I agree with the premise, I can't shake the feeling that something is amiss if this should be considered a normal behaviour of the BM78x series. I have been through many multimeters of several brands and the RM102Pro was the only one that gave me random beeps that I can recall. And I have used and tested many crap and excellent models/brands.
--- End quote ---
There is no way this can be verified without proper testing under controlled repeatable conditions.
I'm not saying it's not a thing, but no one else has reported this, and I am not in a position to test this at present.
Do you have the BM786 and are getting the same problem?
Also, and issue on the Bm786 will almost certainly be present on the other models in that series.
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I don't have the BM786 (I wish), but reading other's comments I suspect I misunderstood the original problem :palm:
My RM102Pro had very occasional beeps if you shook the probes flailing in the air or if only one of them touched a circuit. That is what I read from the original issue and that is a problem in on itself with the meter. If probing and the occasional beep happens, I fully agree the influence of the circuit is to blame here.
--- Quote from: bdunham7 on January 09, 2022, 04:23:38 am ---If you set up a test rig with a capacitor and a bleed resistor (...)
--- End quote ---
--- Quote from: tautech on January 09, 2022, 06:19:15 am ---(...)You can't have super fast continuity and it not also react to probing across a capacitance.(...)
--- End quote ---
--- Quote from: Fungus on January 09, 2022, 09:11:19 am ---(...)As others have said, if you probe a discharged capacitor it will appear as a short-circuit for a fraction of a second. That's electronics.(...)
--- End quote ---
Indeed. I might have misread the original problem.
Meter Deter:
so let me get this straight. its normal to give false beeps?
for me to avoid false beeps i need to drain the capacitors first?
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