Which sequence correctly describes a proper functional test of a sensor circuit to verify connectivity?

• A. Disconnect power, verify continuity across the sensor connections, check ground reference, reapply power and observe sensor output under known stimuli.
• B. Reapply power first, then test output without continuity checks.
• C. Only measure resistance with power on.
• D. Visual inspection of sensor leads only.

Answer: (A)

In a proper functional test of a sensor circuit, you want to confirm both the wiring and the sensor’s ability to respond when powered. Start with the power off to keep you safe and to avoid damaging equipment. Then verify continuity across the sensor connections to ensure there are no breaks in the wiring path. Next, check the ground reference to make sure the sensor and the controller share a solid return path, which is essential for a stable, accurate signal. Once these checks pass, reapply power and observe the sensor output under known stimuli to confirm the sensor actually responds as expected and the signal path remains intact.

Why the other approaches don’t fit: applying power before checking wiring can hide open connections and risks damage or erroneous readings; measuring resistance with power on is unsafe and the readings don’t reflect the sensor’s functional operation; relying on visual inspection alone won’t verify electrical continuity or the sensor’s functional response.