Author Topic: BM869s protection in diode mode?  (Read 814 times)

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Offline Noy

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BM869s protection in diode mode?
« on: July 19, 2019, 08:15:32 pm »
Hello,
I measured with my multimeter BM869s (only half a year old ... :-() a diode and after that the output of a working PFC (420V)
Since it has sparked briefly, I have looked at the setting of my multimeter and thought: "Shit forgot to switch"
I checked voltage and current mode with a DMM Check Plus and against my Fluke 8840A its still working fine.
Diode mode and capacitor mode seem to work also. But i have no idea how I can verify the readings there, at least in diode mode. Does anyone have an idea? A chinese LCR meter and the cheap transistor tester is  available for testing ...
Does anyone know how the diode mode is normally protected within multimeters? Possibly even in my model?
I've looked at the circuit diagram of the 121GW at least one PTC is installed there ...
 

Offline exe

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Re: BM869s protection in diode mode?
« Reply #1 on: July 19, 2019, 08:19:21 pm »
From what I saw in @joeqsmith videos, all input and ranges should be protected.

How you can verify diode mode: just measure diode, hook in parallel another DMM to verify they show the same dropout voltage.

PS may be this video will be helpful:
 

Offline Noy

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Re: BM869s protection in diode mode?
« Reply #2 on: July 19, 2019, 08:30:38 pm »
I do nott have another dmm with diode mode. The Fluke measures diodes in Ohm, so no forward voltage...

Maybe i will find my old uni-t. But i do not know if it has diode mode.
 

Offline exe

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Re: BM869s protection in diode mode?
« Reply #3 on: July 19, 2019, 09:01:48 pm »
Connect your fluke in parallel in voltage mode.
 

Offline windsmurf

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Re: BM869s protection in diode mode?
« Reply #4 on: July 19, 2019, 09:24:03 pm »
Should diode measurements between different multimeters read the same if they're calibrated and reading properly?  From what I understood, you can get different readings depending on the design of the multimeter (different current put through the diode)?  Or is there a current standard?  Pun intended.





 

Offline Noy

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Re: BM869s protection in diode mode?
« Reply #5 on: July 19, 2019, 09:30:24 pm »
@exe good idea. I did not think about that right now. Will try this.
 
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Offline MosherIV

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Re: BM869s protection in diode mode?
« Reply #6 on: July 19, 2019, 10:49:02 pm »
Do not worry too much about it. Dmm like these are properly designed and can take the sort of abuse.

You can check the diode check by a) in diode check setting, short the leads together, the meter should read 0V, b) get a diode measure the diode in both directions - one direction should read the forward V drop (0.7V) the other direction should read open. If this works, your dmm is ok.
 


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