Basic maintenance check: Can an ohmmeter (resistance meter) be used for a simple go/no-go test of a capacitor (e.g., to detect a shorted or open device) even if it cannot measure true capacitance accurately?

Difficulty: Easy

Correct Answer: Correct

Explanation:


Introduction / Context:
Technicians often need a quick field test to identify gross capacitor faults without a dedicated LCR meter. An ohmmeter cannot report capacitance value directly, but it can still reveal shorts, opens, or severe leakage by observing the time-varying resistance as the capacitor charges from the meter's internal source.


Given Data / Assumptions:

  • Handheld ohmmeter provides a small DC voltage for measurement.
  • We look for qualitative behavior, not precise capacitance.
  • Capacitor is discharged before testing; polarity respected for electrolytics.


Concept / Approach:
When connected, a healthy capacitor initially appears as a low resistance (inrush as it charges) and then the indicated resistance rises toward a high value as the charge current decays. A shorted capacitor reads near-zero resistance and stays there; an open capacitor shows no charging action (reading may remain infinite). Excessive leakage yields a steady mid-range resistance. Thus an ohmmeter provides a practical go/no-go assessment.


Step-by-Step Solution:

Discharge the capacitor safely. Connect the ohmmeter and watch the resistance climb in time for a good part. Interpret steady zero as short, infinite as open, mid-range as leaky. Use a proper LCR meter for quantitative capacitance/ESR if needed.


Verification / Alternative check:
Technician guides describe this classic method; bench LCR readings can confirm findings. Oscilloscope with a known resistor can also time the charge curve (V(t) = V_s * (1 − e^(−t/RC))).


Why Other Options Are Wrong:
Incorrect: discards a widely used diagnostic technique.
Only true for electrolytics / above 1 μF: the behavior occurs for any capacitor; larger C simply makes the effect more visible on slow meters.


Common Pitfalls:
Failing to discharge first; reversing polarity on electrolytics; concluding “bad” solely from a fast change on a digital meter with autoranging.


Final Answer:
Correct

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