A photoelectric proximity sensor is an electronic device that detects the presence or absence of an object using light — typically an infrared or visible beam. Unlike inductive or capacitive proximity sensors that rely on electromagnetic or electrostatic fields, a photoelectric sensor works purely on an optical principle, making it suitable for detecting almost any material, including metal, plastic, glass, wood, or even transparent objects.
The sensor consists of three key components — a light emitter, a receiver, and a signal processor. The emitter sends out a beam of light, and when this beam is reflected or interrupted by an object, the receiver detects the change and converts it into an electrical output signal. This signal is then sent to a controller, such as a PLC, to perform a specific action like counting, sorting, or stopping a machine.
Photoelectric proximity sensors are classified into three main types:
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Through-beam type – has separate emitter and receiver units; offers the longest sensing distance and high reliability.
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Retro-reflective type – the light beam is reflected back by a reflector, and any interruption triggers detection.
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Diffuse-reflective type – the sensor detects light reflected directly from the object itself, making it compact and easy to install.
In simple terms, a photoelectric proximity sensor uses light instead of magnetism or capacitance to detect objects. It offers longer sensing ranges, faster response, and versatility, making it ideal for applications like packaging, conveyor systems, object counting, and position detection. Because of its accuracy and non-contact operation, it’s one of the most widely used sensors in modern automation.