Products > Test Equipment
BM235 vs BM867s
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HKJ:

--- Quote from: Fungus on April 07, 2023, 05:36:39 pm ---
--- Quote from: HKJ on April 07, 2023, 04:19:11 pm ---A special LED test socket may be a safety concern (Probably not on the Fluke).

--- End quote ---

If any sparks are big enough to come flying out of those LED test holes then you've probably got more important things to worry about.

--- End quote ---

It is more about isolation distance, CAT III 600V means the isolation must handle 6000V, i.e. a finger on top of the LED socket must not get zapped if 6000V is applied to the measurements inputs.
Fungus:

--- Quote from: HKJ on April 07, 2023, 06:43:58 pm ---
--- Quote from: Fungus on April 07, 2023, 05:36:39 pm ---If any sparks are big enough to come flying out of those LED test holes then you've probably got more important things to worry about.

--- End quote ---
It is more about isolation distance

--- End quote ---

I think that's what I said...  :-//

If any sparks are big enough to get past the input protection components and make it all the way to the top of the meter then you've probably got more important things to worry about.
HKJ:

--- Quote from: Fungus on April 07, 2023, 07:01:57 pm ---
--- Quote from: HKJ on April 07, 2023, 06:43:58 pm ---
--- Quote from: Fungus on April 07, 2023, 05:36:39 pm ---If any sparks are big enough to come flying out of those LED test holes then you've probably got more important things to worry about.

--- End quote ---
It is more about isolation distance

--- End quote ---

I think that's what I said...  :-//

If any sparks are big enough to get past the input protection components and make it all the way to the top of the meter then you've probably got more important things to worry about.

--- End quote ---

You obvious do not get it. The 6000V may come in on the black terminal and it is probably connected with a fairly low impedance to the LED test terminals. The only practical way to protect is distance from terminals inside the meter to the front place. Impedance and/or isolation is not practical in a cheap meter.
Fungus:

--- Quote from: HKJ on April 07, 2023, 07:12:09 pm ---You obvious do not get it. The 6000V may come in on the black terminal and it is probably connected with a fairly low impedance to the LED test terminals. The only practical way to protect is distance from terminals inside the meter to the front place. Impedance and/or isolation is not practical in a cheap meter.

--- End quote ---

Why do you imagine the LED test holes are directly connected in any way to the input jacks? It's not necessary.

(and it's Fluke, they think of these things...)

Edit: FWIW I found a picture of the PCB on the web. Judge for yourself if you think the LED socket is directly connected to the input jacks:
HKJ:

--- Quote from: Fungus on April 07, 2023, 08:03:23 pm ---Why do you imagine the LED test holes are directly connected in any way to the input jacks? It's not necessary.

(and it's Fluke, they think of these things...)

Edit: FWIW I found a picture of the PCB on the web. Judge for yourself if you think the LED socket is directly connected to the input jacks:


--- End quote ---

From the picture it looks like there may be isolation, that is better than I expected, but as I stated initially I expected Fluke to be safe.
I am a bit impressed that Fluke would use money on isolation in a cheap meter (cheap for Fluke).

Without that DC/DC converter block there would not be more than a few kohm from minus input to one of the LED terminals. That would mean higher distances then class II main equipment (Due to the higher voltage). Here the limiting factor is probably creepage under the DC/DC converter.
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