RC integrator fault diagnosis — zero output reading: “If the output of an RC integrator is zero volts, the capacitor might be open.” Decide whether this is a reliable diagnostic conclusion for the standard topology (output across the capacitor).

Difficulty: Easy

Correct Answer: Incorrect

Explanation:


Introduction / Context:
Fault-finding in simple RC networks often relies on qualitative symptoms. In an RC integrator (input → R_series → node → C_to_ground, with output measured at the node across C), a “zero volts” reading at the output suggests a specific type of failure. This question checks whether “capacitor open” is the likely cause or if another fault better explains the symptom.


Given Data / Assumptions:

  • Standard RC integrator topology with output across the capacitor.
  • Assume the input provides a nonzero signal.
  • Measurement made under load that does not by itself short the output to ground.


Concept / Approach:
In the integrator, the capacitor must charge and discharge to develop output voltage. If the capacitor is shorted, the output node is effectively clamped to ground potential, resulting in ~0 V regardless of input (apart from possible small source resistance drops). If the capacitor is open, the node becomes floating; depending on stray/leak paths, the output may drift, show spikes via parasitics, or even mirror portions of the input through stray capacitances—but it is not automatically a rock-solid 0 V. Thus, “0 V ⇒ capacitor open” is not the best conclusion; “0 V ⇒ capacitor short” is more consistent with the observed symptom.


Step-by-Step Solution:

Identify symptom: V_out ≈ 0 V while a signal is applied.Analyze shorted C case: node hard-tied to ground → output forced to ~0 V.Analyze open C case: node floating; without a discharge path, DC may float and AC coupling may produce some nonzero behavior.Conclude that “capacitor open” is not the most plausible cause for a strict zero reading; a shorted capacitor is.


Verification / Alternative check:
Practical troubleshooting guides list “shorted shunt capacitor” as a cause of no output in RC coupling/integrator stages. Replacing the capacitor or lifting one lead to test continuity confirms the diagnosis empirically.


Why Other Options Are Wrong:

  • Correct: Misidentifies the most likely fault given a zero-voltage output.
  • Applies only if series resistor is shorted / Undetermined…: While other faults can also kill the output, the specific claim about an open capacitor being the cause is not reliable.


Common Pitfalls:
Equating “no signal” with any component being open; overlooking that an open component often yields a floating node (undefined), not a hard zero.


Final Answer:
Incorrect.

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