A fork sensor (also known as a slot sensor) is a photoelectric sensor designed in a U-shaped or fork-shaped housing, where the emitter and receiver are built into opposite arms of the fork. It’s used to detect the presence, position, or movement of small objects that pass through the slot. Because the emitter and receiver are factory-aligned in a single compact body, fork sensors offer high precision, easy installation, and reliable operation without the need for external alignment.
The working principle of a fork sensor is based on the through-beam photoelectric detection method. The emitter (usually an infrared or visible LED) sends a continuous light beam to the receiver (a phototransistor or photodiode). When an object — such as a label, paper edge, wire, or packaging material — passes through the fork gap, it interrupts the light beam. This interruption causes a change in the sensor’s output signal, which can then be processed by a PLC or controller to perform an action like counting, cutting, or positioning.
Fork sensors are widely used in label detection, packaging machines, printing, textile, and electronics assembly lines, where high-speed and accurate detection of small parts or materials is essential. They come in various slot widths (typically from 2 mm to 220 mm) and can detect transparent, reflective, or opaque objects depending on the light type and sensitivity settings.
In simple terms, a fork sensor works like a light gate — when something passes through the “U” and blocks the beam, the sensor immediately detects it. It’s a compact, plug-and-play sensor that provides fast, reliable, and maintenance-free detection, making it one of the most commonly used optical sensors in modern automation systems.
A fork sensor is a special type of photoelectric sensor designed in a U-shaped housing. It consists of two key parts — a light emitter on one arm and a receiver on the opposite arm. These components are aligned so the light beam travels across the slot. When an object passes through the fork, it interrupts this beam, and the sensor immediately detects the obstruction. This simple yet effective design makes fork sensors highly reliable in industrial automation.
The working principle of a fork sensor is based on beam interruption. When the light beam remains uninterrupted, the sensor output stays in its normal state. As soon as an object, label, or edge cuts through the beam, the sensor changes its output state, signaling detection. This allows for extremely fast and precise object sensing without any physical contact, reducing wear and maintenance needs in continuous production lines.
Fork sensors are widely used in packaging, labeling, printing, and material handling systems. In packaging machines, they detect label positions and verify presence. In printing systems, they identify edges and marks for alignment. Their compact and pre-aligned design means no complex setup or calibration is required, saving time during installation and maintenance.
Depending on the requirement, fork sensors come in optical, infrared, or ultrasonic types. Optical fork sensors are ideal for label detection, infrared fork sensors work well in dusty environments, and ultrasonic fork sensors handle transparent materials efficiently. Each type offers high response speed and consistent accuracy, even in demanding industrial conditions. In short, a fork sensor works by detecting the interruption of a light or sound beam, providing reliable, fast, and contactless detection essential for modern automation applications.