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Oscilloscope and isolation.

Discussion in 'General Electronics Discussion' started by AcousticBruce, Apr 2, 2013.

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  1. AcousticBruce

    AcousticBruce

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    Apr 1, 2013
    Is there ever a time that hooking your scope up or a isolated transformer vs hooking up what you are testing a good idea?

    Thanks!
     
    Last edited: Apr 2, 2013
  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    It's difficult to understand what you're asking.

    Are you asking when an isolating transformer should be used on either the scope or the device under test?

    I suspect you might be thinking about earth currents that can flow if you connect your ground probe to the wrong place.

    But I'm not sure.
     
  3. AcousticBruce

    AcousticBruce

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    Apr 1, 2013
    I just read that it is not wise to hook your scope up to an isolated transformer that removes the reference to earth ground.

    Is this always the case?
     
  4. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    If I can infer what you're suggesting, it is that you isolate your oscilloscope from the mains and also disconnect the earth wire.

    It's generally discouraged (it's the disconnection from Earth that's the problem -- and also your aim).

    But it may also be required to use your scope in certain circumstances.

    The problem is that you can make the entire scope live (e.g. the case could be effectively connected to the live mains).

    If you're doing this you have to have a damn good reason, know what you're doing, and take many more precautions than usual.

    Frankly, "never" is a good start.
     
  5. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Oh, you're the guy with the semi-dead scope.

    If you're working on the scope, maybe an isolating transformer could help (not much point if it already has a transformer). Disconnecting the Earth would be something I would NEVER do.

    Even with the mains isolated by a transformer, the voltage is still there and is just as deadly. Also there are even higher voltages than mains, and they'll give you a kick that you'll never forget. (I've had 300VDC from a low impedance source an that was enough to put me off ever wanting another one -- and 300V is small bickies)
     
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