Photoelectric sensors, also called photocells, use light to detect the presence or passage of objects without physical contact. Typical applications include counting products on conveyors, checking packaging and detecting positions on machinery. The appropriate model depends on the target, sensing distance and available mounting space.

Diffuse-reflective sensors detect light reflected by the target and require no separate reflector; target color and surface finish affect selection. Retro-reflective sensors detect an interruption of light returning from a reflector mounted opposite the sensor. Through-beam sensors have separate emitters and receivers, requiring mounting and electrical connections on both sides.

Fiber optic sensors use small sensing heads to reach confined spaces; check compatibility between the fiber unit and amplifier. When choosing distance measuring sensors, compare measurement range, accuracy, repeatability and the output used to transmit the measured value.

Specialized options include label and label-gap detection sensors, color recognition sensors and sensors for monitoring yarn movement or breakage. Safety light curtains are assessed separately for machine safety applications.

Compare supply voltage, PNP/NPN or relay output, response time, housing dimensions and environmental requirements. Check output compatibility with the connected controller and the required Light-ON/Dark-ON operating mode. Transparent or reflective targets require a model suited to that application. The ultrasonic sensors linked in this section use sound rather than light and provide a different sensing option.