| Electronics > Beginners |
| Probing usb powered circuit. Should I be scared? |
| << < (4/7) > >> |
| Moriambar:
Oh lord, there seems to be no end to this, what have I done? :D |
| GeoffreyF:
Always check the grounds to assure they are at the same potential. At the least your scope measurement will not be accurate if there is even a small amount of current flowing through the ground or a difference in ground potentials. Technicians supporting rock concerts also check this before a performance. In a mild case, there is a hum which ruins the performance. If the potential difference is enough it can kill. An example would be a microphone amplifier connected on one side of the stage and a guitar amplifier on the other. The grounds are far enough apart that there can be an even lethal potential difference. Nowadays, most use wireless transmitters which removes the problem. I once saw this problem in a friends kitchen. The metal case of the refrigerator had that false texture which represents current flow. Someone had done an amazingly bad job of connecting the mains socket for the fridge and it was not properly grounded. I fixed it and fortunately nobody was hurt before that. "The art of electronics" by Paul Horowitz and Winfield Hill discusses this from a measurement and safety point of view. I recommend the book for many reasons but one of them is that. |
| Moriambar:
--- Quote from: GeoffreyF on October 19, 2018, 01:01:15 pm ---Always check the grounds to assure they are at the same potential. At the least your scope measurement will not be accurate if there is even a small amount of current flowing through the ground or a difference in ground potentials. Technicians supporting rock concerts also check this before a performance. In a mild case, there is a hum which ruins the performance. If the potential difference is enough it can kill. An example would be a microphone amplifier connected on one side of the stage and a guitar amplifier on the other. The grounds are far enough apart that there can be an even lethal potential difference. Nowadays, most use wireless transmitters which removes the problem. I once saw this problem in a friends kitchen. The metal case of the refrigerator had that false texture which represents current flow. Someone had done an amazingly bad job of connecting the mains socket for the fridge and it was not properly grounded. I fixed it and fortunately nobody was hurt before that. --- End quote --- Ok, I'll try and measure... --- Quote ---"The art of electronics" by Paul Horowitz and Winfield Hill discusses this from a measurement and safety point of view. I recommend the book for many reasons but one of them is that. --- End quote --- I have the book (although I have not read it cover to cover, just skimmed about some parts that interested me), can you please point me to where they discuss this? It sounds interesting |
| ebastler:
--- Quote from: Moriambar on October 19, 2018, 12:42:01 pm ---Oh lord, there seems to be no end to this, what have I done? :D --- End quote --- This thread is no longer yours... ;) Actually, the thread is doing fine. Everybody is actually still discussing the original topic! :) |
| Moriambar:
--- Quote from: ebastler on October 19, 2018, 01:26:47 pm --- --- Quote from: Moriambar on October 19, 2018, 12:42:01 pm ---Oh lord, there seems to be no end to this, what have I done? :D --- End quote --- This thread is no longer yours... ;) Actually, the thread is doing fine. Everybody is actually still discussing the original topic! :) --- End quote --- I meant that I thought to ask a simple question and to get a boring universal answer... Instead this interesting discussion has come along, and I hope to learn the most from it |
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