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

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SUMMARY

An oscilloscope can measure DC and AC signals differently due to the presence of a capacitor that filters DC when the AC setting is selected. When the input selector is set to DC, the oscilloscope can display a voltage reading even if the probes are reversed, as it measures the absolute voltage level. However, in AC mode, the oscilloscope does not display a waveform for DC signals because the capacitor blocks the DC component, resulting in only a horizontal trace. This behavior is crucial for understanding how oscilloscopes interpret different types of signals.

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  • Understanding of oscilloscope operation and settings
  • Knowledge of AC and DC signal characteristics
  • Familiarity with capacitive filtering in electronic circuits
  • Basic principles of voltage measurement
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  • Research the function and types of capacitors used in oscilloscopes
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  • Investigate the role of probes and their positioning in oscilloscope measurements
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Electronics students, engineers, and technicians who work with oscilloscopes and need to understand signal measurement techniques for both AC and DC signals.

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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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