Mistake-Proofing Resource Center

Photoelectronic Sensors

There are three main types of photoelectric sensors:

  • A through-beam unit has a light source and a separate receiver. It looks for the beam between the two to be broken.
  • A reflective unit has the receiver in the same unit as the light source and looks for the “bounce-back” of the light off an object.
  • Retro-reflective units bounce a light source off a reflector and sense when this beam is broken.


  • Sensing of tank or bin level.
  • Confirmation of part or object passage.
  • Detection presence or absence of object.
  • Positioning of work piece.
  • Measuring distance.


  • Non-contact.
  • Works in harsh environments.
  • Detects targets of almost any material.
  • Color discrimination capabilities.
  • Capable of long detecting distances.
  • Can have high accuracy detection.