Comments on Is it always necessary to use the ground terminal of the oscilloscope probe?
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Is it always necessary to use the ground terminal of the oscilloscope probe?
Assume my oscilloscope is grounded, and the DUT is grounded as well (earth ground). I am using a standard 10 Mohm impedance 1:10 passive probe. So, the ground terminal of the probe is in fact connected to earth through the oscilloscope chassis.
Is there any reason to connect the ground tip of the probe to the ground of the DUT?
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To add to Olin's excellent answer, if you were probing on a digital IO line in order to view a fast changing signal, without the local ground clip (or spring) grounded close to where you make the measurement, you would, in effect, be adding an antenna to that IO line and causing interference to other parts of the circuit and even other circuits in the same vicinity. The signal captured by your o-scope would contain all-manner of unwanted artefacts as well.
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