Question copied from a thread on EEVblog by Serge 125
For as long as I can remember I would like learn how to check voltage on a live circuit but I've looked every where in books, vids etc.... for any detail on how to do this and I just can't find this. I remembering a long time ago I did poked on a live circuit and fried something and since then I have never poked on live circuit because I'm afraid to short something and make things worse. Mr EEVblog you have a MASSIVE vid collection on YT, but I don't know if you have one that explains how to check live voltage values on circuit boards
At a very fundamental level, any voltage you will measure is at a potential with reference to some other point of the circuit...
Usually 0V, or often that’s tied to GROUND, but [WARNING] you can’t guarantee that.
Consider that some voltages may be AC, so your readings, method and range of measurement will be different from DC measurements.
And finally, do your research on WHAT you’re probing. mains-level voltages (AC or DC), can kill you in a dozen different ways.
... and a quick reminder. If your meter is set to a current range (A or mA), that presents virtually a short-circuit across the probes. Don’t forget, when measuring a voltage in the current ranges will usually fry your device or meter?
Mains voltage did not kill me.
But almost.
The devil did not want me.
Yet.
I am now enjoying my second life.
I have now a permanent scar at my hand where the current entered.
It went out along my feet passing through the heart line.
@RIN6730 welcome back to Earth (literally). Many of us have had ‘small’ mains shocks, but you were very lucky.
A sensitive photo of your ‘scarf’ may help to pass on the risk/severity to the kids and tinkerers here. Glad you made it through.
lastchancename:
@RIN6730 welcome back to Earth (literally). Many of us have had ‘small’ mains shocks, but you were very lucky.
A sensitive photo of your ‘scarf’ may help to pass on the risk/severity to the kids and tinkerers here. Glad you made it through.
Twenty-five years after, my finger scar is not very spectacular any more:
It was just at the point where my finger did hold the plier at the end of the insulation.
I just could not unclasp the plier until I fell consciousless.
It was newertheless a third grade burning (painless, as all nerves are burnt).
You were VERY LUCKY !
Enough said.
@deepak, Not a bad example, but my meters don’t have a mAVΩ position... not many do.
Perhaps add some photos or diagrams (in-line) to show the methods, and break up your paragraphs to be more readable, particularly as you introduce steps. This has to be extremely clear and simple for beginners.
You can update your first post since you’re not changing anything.
+karma
