EEVblog Electronics Community Forum
Electronics => Beginners => Topic started by: d4n13l on March 12, 2016, 06:37:00 pm
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Hi everyone,
So I manage to get an oscilloscope, which I'm starting to learn how to use. I know that the probes are connected to earth ground through the power cord, however at home there aren't power sockets with a ground slot. So I want to know if would there be any problem if I use the oscilloscope without grounding it to earth.
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It won't be too much trouble providing you stick to low voltage circuits. The thing you need to bear in mind is that the ground is the whole Chasse of the oscilloscope and the ground clips of the probes and the metal parts of the BNC sockets on your scope. So the essential thing is that the Chasse does not end up at a dangerous potential with respect to ground because you touch it in use. If you're going anywhere near the mains it needs grounding.
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Any mains appliance with a 3 core mains lead must be grounded, whether they are washing machines or Oscilloscopes. This is required for electrical safety. The only things safe without a ground are specifically designed double insulated products with 2 core mains lead. Sorry, but there is no alternative.
EDIT: Sorry, just re-read your original post and realized that you have no grounded outlets. In that case it's not so easy, you need to arrange some sort of local equipotential system so that it is impossible to touch two cabinets or pieces of metalwork at different potentials.
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You'll need to tell us a bit more about the building you are in. Would it be possible to drive an Earth rod outside and run a heavy wire to your workbench? Are there any metal waterpipes in the room and are they grounded?
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I'm on a 3rd floor apartment and the bigger piece of metal I can see is an 2x2m window frame next to my room window. I think that driving an Earth rod outside would be troublesome.
However for the near future I think I'll only work on low voltage circuits. So it should be ok right?
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You've got problems. Without a ground, significant voltages can be present between the chassis of different items of mains powered test equipment, easily enough to blow sensitive chips. The leakage current is limited by design and for any single piece of test equipment should be touch-safe for a human, but if you bond all the grounds together the leakage currents can add up and become unsafe. If your apartment building has a steel or reinforced concrete frame, any added equipotential bonding *MUST* make a good connection with either ground or the building frame or concrete reinforcement as the floors and walls can provide a low enough resistance to ground for an ungrounded equipotentially bonded area to be hazardous.