Michelin ECT GAP Practice Test 2026 - Free Practice Questions and Study Guide

For a Retro-reflective Photo Detector, the correct output state when the target is present is "ON." This type of sensor works by emitting a light beam, usually infrared, toward a retro-reflective surface. When the target (the retro-reflector) is in the path of the emitted light and reflects it back to the sensor, the detector recognizes the presence of the target and activates its output, signaling that the target is there.

Understanding how retro-reflective sensors work is important because their function relies on the return of the emitted light. If the target is absent, the light does not return, and therefore the sensor remains off or in a low state, indicative of no detection. Thus, when the target is indeed present and reflecting light back to the sensor, the output will be "ON."