Author Topic: DMM safety  (Read 2769 times)

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Offline Fungus

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Re: DMM safety
« Reply #25 on: December 02, 2022, 02:43:03 pm »
The reason I'm asking my original question is that I'm currently looking at a meter that noone, including Joe has tested yet. The Brymen BM089 which according to its datasheet complies with:

UL/IEC/EN61010-1 Ed. 3.0, IEC/EN61010-2-033 Ed. 1.0, CAN/CSA C22.2 No. 61010-1 Ed. 3.0, IEC/EN61010-2-032 Ed. 3.0 & IEC/EN61010-031 Ed. 1.1:Measurement Category III 1000V & Category IV 600V AC & DC.

If Bryman says that in the user manual then it's a safe bet that it met those standards.

So the question is basically does any of the aforementioned safety-standards imply that they actually tested the meter with all three leads connected to mains and put it in the µA range and it didn't blow up?

Yes.
 
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Offline Fungus

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Re: DMM safety
« Reply #26 on: December 02, 2022, 02:46:00 pm »
If you look at the specs more closely though, they say that the DC µA range of that meter has a burden voltage of 3.5mV/µA aka. 3.5kV/A which is pretty high. Still DC µA will create a short across the mains and there is a lot of energy involved...

The uA range is for measuring flame sensors so it will have a very limited range, hence the high burden voltage.

(and also the safety rating - the internal resistance in uA mode is nowhere near zero so only a low current will pass).
 
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Offline BeBuLamar

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Re: DMM safety
« Reply #27 on: December 02, 2022, 02:46:11 pm »
Thanks! I didn't know but when I called Fluke and told them they said it's underwarranty. Just have to send the old one for them to destroy they send me a new one.
 

Offline tautech

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Re: DMM safety
« Reply #28 on: December 02, 2022, 05:51:20 pm »
If you look at the specs more closely though, they say that the DC µA range of that meter has a burden voltage of 3.5mV/µA aka. 3.5kV/A which is pretty high. Still DC µA will create a short across the mains and there is a lot of energy involved...

The uA range is for measuring flame sensors so it will have a very limited range, hence the high burden voltage.

(and also the safety rating - the internal resistance in uA mode is nowhere near zero so only a low current will pass).
:-//
Maybe you have never built and needed to measure the quiescent draw of a micro power device.
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Offline Fungus

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Re: DMM safety
« Reply #29 on: December 02, 2022, 06:16:11 pm »
Maybe you have never built and needed to measure the quiescent draw of a micro power device.

I've built a lot of coin cell powered devices that lasted for years.

OTOH I wouldn't want "flame sensor test" to be the only uA range on my multimeter, and I certainly wouldn't want that huge burden voltage.
 

Offline BeBuLamar

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Re: DMM safety
« Reply #30 on: December 02, 2022, 06:27:07 pm »
Actually I bought the meter because the guys need to measure flame rod current and I can measure flame current well with very high burden voltage (the voltage that feed the flame rod is about 400V). That turns out to be a good things because I am afraid that someone will try to measure voltage with the selector set at microamps.
 
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Offline TracelessTopic starter

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Re: DMM safety
« Reply #31 on: December 03, 2022, 11:29:29 am »
You specifically mentioned 1.7V lithiums. I guess you are going to discharge them a bit or put a schottky or germanium diode in series with them. Because some meters like Brymen 235 don't accept them. At least they'll not leak.

I didn't know that Brymen meters had problems with Lithium batteries. I'll check back with Brymen and ask them if those are okay for that meter.

I haven't used many meters personally but a few meters that I have used so far that have high input impedance can do that trick (shows higher voltage when input jack is connected to phase than to the neutral).
Edit: Oh, I forgot to mention that in my humble opinion, it is always best to use fused probes like Fluke FTP with industrial mains regardless what meter someone is using.

I have noticed that too but not sure if I would trust this to work reliably every time - sometimes the readings are pretty similar. My favourite trick so far was remove the leads from the DMM touch one of the terminals with a disconnected lead and then use the NCV against the lead to detect the phase. While that works, the brymen's single probe voltage detection is more convenient. Of course it is not an indispensable feature, you could also always use a regular DMM + one of those flim-flam-sticks, I really like the swiss-army-knife nature of that particular brymen model it just replaces a lot of dedicated tools.

Sorry about that. I used it only as an example and suggested only for industrial work. There are a few other manufacturers in Europe offering fused probes, fused leads and even small fused attachment that connects directly to the meter and accepts normal probes.

Thanks for mentioning it I've never thought about fused probes. As you said those are probably well suited for industrial high energy work. For regular CAT II/III stuff it is probably overkill plus those probes can also be a safety hazard if you are not super diligent with testing your equimpment before every measurement. If the probe fuse is open circuit and you think a circuit is not energized when it is still live there might be an upleasant surprise around the corner.
 


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