Ground Safety - Page 1
Forum section: electronics / projects

author: dstrukov
author_rank: Newbie
timestamp: December 12, 2012, 09:23:41 pm
content: Have a small question about work safety if you do not own an isolation transformerShould 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

author: dstrukov
author_rank: Newbie
timestamp: December 12, 2012, 09:36:08 pm
content: I realized that this is the wrong board. Can someone move this to Beginners board

author: dstrukov
author_rank: Newbie
timestamp: December 12, 2012, 11:18:54 pm
content: how about if circuit is out of the enclosure .... on the benchdoes that make any difference?

author: Things
author_rank: Regular Contributor
timestamp: December 13, 2012, 05:34:28 am
content: 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.

author: StubbornGreek
author_rank: Frequent Contributor
timestamp: December 13, 2012, 06:52:25 am
content: 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?

author: dstrukov
author_rank: Newbie
timestamp: December 13, 2012, 09:57:13 am
content: 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 ishighly recommendedmandatory 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?

author: slashguitar
author_rank: Contributor
timestamp: December 13, 2012, 10:23:44 am
content: Regarding the ESR measurement, take a look at howBob Parker ESR meterworks. 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

author: dstrukov
author_rank: Newbie
timestamp: December 13, 2012, 10:37:17 am
content: Thanks for the great link. Seen bits and pieces of it, but never found a full article. Thanks