Why can an oscilloscope have the probes changed in position and have a

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Discussion Overview

The discussion revolves around the behavior of oscilloscopes when measuring DC and AC signals, specifically addressing why changing probe positions affects readings differently for DC and AC currents.

Discussion Character

  • Technical explanation, Conceptual clarification, Debate/contested

Main Points Raised

  • One participant questions why an oscilloscope can show a DC current reading when probes are switched, but not for an AC current.
  • Another participant notes that oscilloscopes measure voltage, implying that current measurements would require a current transducer.
  • A participant describes their experience of switching the input selector to DC, resulting in a downward trace movement, and contrasts this with the lack of waveform when the selector is on AC.
  • One participant explains that a capacitor filters out the DC component of the signal when AC is selected, suggesting that this is why a DC signal can only be measured with the DC setting.
  • It is mentioned that either AC or DC settings can work for measuring an AC signal.

Areas of Agreement / Disagreement

Participants express differing views on the implications of switching probe positions and settings, with no consensus reached on the underlying reasons for the observed behavior of the oscilloscope.

Contextual Notes

The discussion does not clarify the specific configurations of the oscilloscope or the nature of the signals being measured, leaving assumptions about the setup and definitions of AC and DC signals unresolved.

Who May Find This Useful

Individuals interested in oscilloscope operation, electrical engineering, and signal measurement may find this discussion relevant.

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Why can an oscilloscope have the probes changed in position and have a dc current reading but not for an ac current? I put the oscilloscope leads with the probe at D and the ground side at A, and there was no waveform, why is this?
 
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Scopes measure voltage so unless you had a current transducer I am not sure what you measured.
 


I turned the input selector switch to DC and the trace moved downward about 5 divisions, representing -10 V. When I did it with the selector switch on AC, there is no waveform apart from the horizontal trace. Why was it possible to reverse the oscilloscope leads with the DC circuit switch but not with the AC circuit switch?
 


There is a capacitor that filters out the DC of the signal when AC is selected. So if you send a DC signal to a scope the only way to measure it is with DC selected. To measure an AC signal, either AC or DC will work.
 

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