Text: A noncontacting transducer which detects the level of reflectivity of an observed surface. A light-emitting diode, operating in the infrared region, provides a light source out the tip of the transducer. When light is reflected back to the transducer from the observed surface, it is focused by the transducer lens into an infrared sensitive phototransistor whereby a voltage is generated. The most common application is as a temporary Keyphasor transducer observing a once-per-turn change in reflectivity (dark or light paint spot or strip of reflective tape) on the shaft.

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