Glossary · Sensors and measurement
Through-beam photoelectric sensor
Also known as: Through-beam sensor, Opposed-mode sensor
German: Einweglichtschranke
In industrial automation, a through-beam photoelectric sensor is a photoelectric sensor with separate emitter and receiver facing each other; it detects an object when the object interrupts the light beam between them.
- Sensors
- Standards
In one sentence
A through-beam photoelectric sensor uses separate emitter and receiver and detects objects when they interrupt the beam between them.
Example
A through-beam photoelectric sensor across a wide conveyor detects dark, matte parts that a diffuse sensor would miss.
How it applies
- Engineering: Through-beam sensors have the longest range and the highest switching reserve of photoelectric sensors and work largely independently of object color and surface. They require wiring on both sides.
- Commissioning: Align emitter and receiver precisely; check that reflections from shiny surfaces cannot bypass the object.
- Safety: Single-beam or multi-beam safety light barriers are designed and rated as protective devices. A standard through-beam sensor is not one, even though the principle looks the same.
- Documentation: Specify range, alignment and cleaning in the maintenance manual, and label process sensors and protective devices distinctly in drawings.
Through-beam vs. diffuse-reflective sensor
A through-beam sensor needs two devices but offers long range and reliability. A Diffuse-reflective photoelectric sensor needs only one device but depends on the object's surface.