A background check for photoelectric sensors

摘要

Consider a photoelectric sensor operating in simple diffused mode (i.e., as a proximity sen-sor). The sensor uses the tar-get to reflect light back and senses the reflection as an indication of the target's presence. A point to note is such applications work properly without a secondary device such as a reflector. But there is a downside to working without a reflector: It may be tough to precisely control the sensing range even if the sensor has a sensitivity adjustment. This conundrum can cause significant problems when sensitivity is such that the sensor accidentally triggers on shiny objects well beyond its specified sensing range. In fact, it is not uncommon for a sensor with a specified range of 15 in. to falsely detect a piece of metal, Plexiglas, or other highly reflective object 6 ft away or more.