Electronics > Beginners
OScope Safety Question
David Hess:
--- Quote from: KungFuJosh on September 03, 2018, 10:19:22 pm ---Nope. The "genius" uses ungrounded DUTs on ITs. Exactly what I wrote. He literally has a video on youtube where he demonstrates doing that. :palm: :palm: :palm:
Sorry if the quotes on "genius" didn't convey my sarcasm strongly enough. ;)
--- End quote ---
Ah, well I do not know why one would bother doing that except in special circumstances. One might for instance want to disconnect the chassis ground so that one does not inadvertently ground oneself or something else while poking about inside while the DUT is energized. I might also want to use a different ground in place of the AC power ground if I thought electrostatic coupling was causing a problem.
--- Quote from: ogden on September 03, 2018, 10:43:45 pm ---When you connect scope ground clip to your device somewhere, you effectively ground that particular point of circuit to scope ground AND chassis of device. I do not find this safe, especially for your scope. Slightest error of yours or problem with equipment under test and least of your problems could be shopping for new scope.
You definitely shall use probe that is safe w/o isolation transformer.
--- End quote ---
That is why I mentioned attaching a real ground connection to the point where the oscilloscope's probe ground is connected. At least then if there is a fault, some or most of the current will be diverted away from the oscilloscope. It is not always feasible to avoid using a probe ground with differential probes although newer ones usually do not provide the option to do so even if you wanted to.
KungFuJosh:
--- Quote from: David Hess on September 03, 2018, 10:49:49 pm ---Ah, well I do not know why one would bother doing that except in special circumstances. One might for instance want to disconnect the chassis ground so that one does not inadvertently ground oneself or something else while poking about inside while the DUT is energized. I might also want to use a different ground in place of the AC power ground if I thought electrostatic coupling was causing a problem.
--- End quote ---
Well, in my case and his, we're talking about tube guitar amplifiers. There's always a metal chassis, and whether or not it's grounded is kinda a big deal. I know people can get away with doing that, but it's...so...stupid.
--- Quote ---That is why I mentioned attaching a real ground connection to the point where the oscilloscope's probe ground is connected. At least then if there is a fault, some or most of the current will be diverted away from the oscilloscope. It is not always feasible to avoid using a probe ground with differential probes although newer ones usually do not provide the option to do so even if you wanted to.
--- End quote ---
My differential scope is powered by USB on the oscilloscope. Should I not do that, or is it cool?
ogden:
--- Quote from: KungFuJosh on September 03, 2018, 10:46:50 pm ---
--- Quote ---You definitely shall use probe that is safe w/o isolation transformer.
--- End quote ---
I think something is lost in translation here. What do you mean?
--- End quote ---
Yes, it's late here. Ignore that. If every voltage you measure in tube amp is chassis-referenced, then all you need is hi-voltage 1:100 probe, or two. Original probe is 150V rated in 1:1 and 300V rated in 1:10, I would not use such in 400..500VDC (or whatever voltages you have there) tube amp, especially knowing how sloppy that switch is.
David Hess:
--- Quote from: KungFuJosh on September 03, 2018, 11:26:26 pm ---
--- Quote ---That is why I mentioned attaching a real ground connection to the point where the oscilloscope's probe ground is connected. At least then if there is a fault, some or most of the current will be diverted away from the oscilloscope. It is not always feasible to avoid using a probe ground with differential probes although newer ones usually do not provide the option to do so even if you wanted to.
--- End quote ---
My differential scope is powered by USB on the oscilloscope. Should I not do that, or is it cool?
--- End quote ---
It does not matter either way. Just use it as designed.
KungFuJosh:
--- Quote from: ogden on September 03, 2018, 11:38:24 pm ---Yes, it's late here. Ignore that. If every voltage you measure in tube amp is chassis-referenced, then all you need is hi-voltage 1:100 probe, or two. Original probe is 150V rated in 1:1 and 300V rated in 1:10, I would not use such in 400..500VDC (or whatever voltages you have there) tube amp, especially knowing how sloppy that switch is.
--- End quote ---
I've changed my setup, but I'm well covered. I returned the DS1054Z and bought a Siglent SDS1104X-E instead. I have Pico TA131 250MHz probes, which are rated 600V in 10X, and I have a BK PR2000B 100X probe that's rated 2000V. I did also buy a differential probe, but that's 1300V at 500X, which isn't always useful.
Navigation
[0] Message Index
[#] Next page
[*] Previous page
Go to full version