| Electronics > Repair |
| Weird USB oscilloscope ground issue? |
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| m k:
Different grounds can have different levels on purpose. 180mA can be an overcurrent protected short. |
| magic:
--- Quote from: wraper on June 23, 2024, 08:25:35 am ---To the level of what he'd seen it's not normal. --- End quote --- Fair enough, I measured my own computers and found only up to 10mV between USB port grounds and PSU chassis under full load, so 250mV may be a little excessive. I also have a few mV difference between the chassis and earth on a nearby mains socket, indicating that I already have ground loops sending DC through mains earth, maybe through the monitor. |
| Alex_Baker:
I have tested earth paths around my workbench, which is where I am using the scope. I have not tested the earth path of the actual outlets in the wall since that would need me to turn the power off, but other than that I have not found any problems. Correct me if I am wrong, but I don't think this stray current issue actually poses any risk to me or my electronics, so I don't think it is worth chasing any more. If I had to guess, a mixture of long usb cables and a sub-optimal set of power strips feeding my PC and workbench make this seem much worse than it normally would be. |
| wraper:
--- Quote from: Alex_Baker on June 26, 2024, 03:49:02 pm ---I have tested earth paths around my workbench, which is where I am using the scope. I have not tested the earth path of the actual outlets in the wall since that would need me to turn the power off, but other than that I have not found any problems. Correct me if I am wrong, but I don't think this stray current issue actually poses any risk to me or my electronics, so I don't think it is worth chasing any more. If I had to guess, a mixture of long usb cables and a sub-optimal set of power strips feeding my PC and workbench make this seem much worse than it normally would be. --- End quote --- You don't need to shut down the power to check the earth connection. Yes it poses safety risk as some devices my be working without proper protective earth connection. |
| Alex_Baker:
--- 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. |
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