Ground Safety

[dstrukov]

Have a small question about work safety if you do not own an isolation transformer

Should the AC appliance be connected to ground while you are working with it?

(example: A power supply.)

Everyone, please share your opinion.
If you know what you are talking about, please elaborate.

EDIT: Even If you are unsure about the answer, please vote for the one that seems most plausible to you. Thanx

[dstrukov]

I realized that this is the wrong board. Can someone move this to Beginners board

[dstrukov]

how about if circuit is out of the enclosure .... on the bench
does that make any difference?

[Things]

AC appliances should always be connected to ground unless they're double isolated.

Although it may seem counter intuitive, in case you accidentally touch a live part while leaning on the case, most houses these days have a GFI that should interrupt the circuit very quickly in such a situation. If you don't have a ground connected, chances are the power would stay on.

[StubbornGreek]

This depends on the test equipment you're using. If you're using a battery powered handheld, then no worries but if you're probing around with an oscilloscope, make sure not to create any ground loops or you'll not have a good day, seriously.

Do you have access to an isolation transformer (not a medical grade type)? That would be your best solution - oh and remember, its the DUT not the test equipment you connect to the iso.

EDIT: Could you be a bit more specific? What device and equipment are you using and what are you trying to accomplish?

[dstrukov]

Thank you all for your responses. I am troubleshooting an ATAG induction cooking plate. It has blown one of the PCB tracks during cooking ... The track was meant to blow as a fuse. I found a short on the circuit and replaced the shorted part (a relay). but the thing still refuses to work correctly. I did poke around with oscilloscope a bit while it was connected in its place, but it is not exactly comfortable to work in the kitchen. So I took the whole thing to my bench and now struggling on the safest way to connect it.

Thanks for pointing out the GFI or residual-current device (RCD)  ... totally forgot about those. Indeed, if you have those installed in your home, then it is highly recommended mandatory to ground everything.

But the best idea to date, i guess, is to get an isolation transformer. By the way, the medical grade transformer will also do good (as usual - my amateur opinion, NOT a fact), BUT you will have to modify it first. The mod is simple - cut off the ground wire going to the secondary coil of the transformer. By doing that you de-reference the secondary coil from the ground.

I am using a Rigol DS1052E to probe around.
If I have a ground lead connected, I remove the ground lead from my probe, so it does not touch anything by accident. In case I want to do differential measurements, I would use both channels on my  oscilloscope and a Math function to get the difference.

Perhaps off-topic:
I do not have an ESR meter, but I try to get around with my signal generator (to generate 100kHz square) + oscilloscope to measure voltage drop. Gives me (I think ... please tell me if I'm wrong) a rough indication of ESR.  If square wave flats out - ESR is low ... The higher the amplitude of the square wave, the higher the ESR. Right?

[slashguitar]

Regarding the ESR measurement, take a look at how Bob Parker ESR meter works. You should generate a narrow pulse(so the capacitor doesn't charge) and the voltage you see on the scope should be the voltage drop on the ESR

[dstrukov]

Thanks for the great link. Seen bits and pieces of it, but never found a full article. Thanks