Glossary · Sensors and measurement
Light barrier
Also known as: Light beam sensor
German: Lichtschranke
In industrial automation, a light barrier is a photoelectric sensor that detects an object when it interrupts a light beam, either between a separate emitter and receiver (through-beam) or between the sensor and a reflector (retro-reflective).
- Sensors
In one sentence
A light barrier detects objects by the interruption of a light beam between emitter and receiver or between sensor and reflector.
Example
A retro-reflective light barrier across a conveyor counts packages as they interrupt the beam to the reflector.
How it applies
- Engineering: Through-beam light barriers have the longest range and are largely independent of object surface; retro-reflective types need only one electrical connection side. Transparent or shiny objects may need polarization filters or special variants.
- Commissioning: Align emitter, receiver or reflector and check the switching reserve. Contaminated optics reduce the reserve and cause failures.
- Safety: A standard light barrier is a process sensor. A single-beam safety light barrier or Safety light curtain used for safeguarding is a rated Active opto-electronic protective device (AOPD) and must be integrated into a designed safety function.
- Documentation: In the operating manual, distinguish process light barriers from protective devices and give cleaning intervals for the optics.
Light barrier vs. safety light curtain
The German term Lichtschranke is used for both process sensors and safety devices. In English documentation, write light barrier or photoelectric sensor for process sensors and name protective devices explicitly.