| Electronics > Repair |
| Weird USB oscilloscope ground issue? |
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| wraper:
--- Quote from: Alex_Baker on June 26, 2024, 04:06:00 pm --- --- Quote from: wraper on June 26, 2024, 04:01:13 pm ---Yes it poses safety risk as some devices my be working without proper protective earth connection. --- End quote --- I have tested all the earthed devices in this room, I cant find anything wrong with any of them. --- End quote --- So what? Device can be 100% fine but dangerous at the same if there is an issue with mains wiring. |
| Alex_Baker:
How about this, I know that there exists and earth connection between my workbench and my PC, which are on different wall outlets. I know one exists because I can create a current loop by connecting my scope ground to earth at my workbench, which must mean that current is flowing back to the PC through the outlet earth wiring. I don't exactly know the condition of the earth path, but it cant have too high a resistance or 100mV would not result in much current flow. |
| m k:
Famous last words. Here all deadly electric accidents have had two faults. You seem to have one already. |
| magic:
If there is abnormally high voltage between different "grounds" in the PC then the problem is likely in the PC. If in doubt, disconnect everything from it and measure if the motherboard to case offset is still there. Theoretically, there is possibility that something else is broken and sends tons of DC through a ground loop passing through its PC connection cable, the PC and mains earth, but IMO the PC is the chief suspect. |
| Alex_Baker:
--- Quote from: m k on June 26, 2024, 06:35:43 pm ---Famous last words. Here all deadly electric accidents have had two faults. You seem to have one already. --- End quote --- I get the message, thanks --- Quote from: magic on June 26, 2024, 11:05:14 pm ---If there is abnormally high voltage between different "grounds" in the PC then the problem is likely in the PC. If in doubt, disconnect everything from it and measure if the motherboard to case offset is still there. Theoretically, there is possibility that something else is broken and sends tons of DC through a ground loop passing through its PC connection cable, the PC and mains earth, but IMO the PC is the chief suspect. --- End quote --- I could not find anything that was more than 6mV. |
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