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According to the detection method, photoelectric switches can be classified into diffuse-reflective, through-beam, retro-reflective, slot-type, and fiber-optic photoelectric switches.
The through-beam type consists of a transmitter and a receiver, which are structurally separate. In the event of interruption of the light beam, a switch signal change is generated. A typical arrangement is that through-beam photoelectric switches located on the same axis can be separated from each other up to 50 meters.
Characteristics: able to detect opaque reflective objects; large effective distance, as the only needs to traverse the sensing distance once; resistant to interference, suitable for reliable use in outdoor or dusty environments; high device consumption, as both units require cable installation.
In diffuse-reflective type, when the switch emits the beam, the target produces diffuse reflection. The emitter and receiver constitute a single standard component, and the switch state changes when sufficient combined light returns to the receiver. The typical value of the operating distance is generally up to 3 meters. Characteristics: the effective operating distance is determined by the target's reflectivity, influenced by the surface properties and color of the target; smaller assembly costs, as positioning can usually be achieved roughly with a single component switch; measurement distance adjusted by background suppression function; sensitive to dust on the target and changes in the target's reflective performance.
Mirror reflection is a standard configuration where the sensor consists of an emitter and a receiver. The light beam emitted by the emitter is reflected by a mirror on the opposite side and returns to the receiver. When the light beam is interrupted, a change in the switch signal occurs. The time it takes for the light to pass through is twice the duration of the signal, and the effective operating distance ranges from 0.1 meters to 20 meters. Its characteristics include the ability to detect opaque objects, the use of mirror components to achieve a high effective distance range, and resistance interference, making it suitable for reliable use in outdoor or dusty environments.
Slot-type photoelectric switches are typically a standard U-shaped structure, with the emitter and receiver located on opposite sides of the U-shaped slot, forming an optical axis. When the detected object passes through the U-shaped slot and interrupts the optical axis, the photoelectric switch generates a detected switching signal. Slot-type photoelectric switches are safe and reliable for detecting high-speed changes and differentiating between transparent and translucent objects.
Fiber-optic photoelectric switches use plastic or glass fiber optic sensors to guide light and enable detection of objects in distant areas. Fiber optic sensors are typically divided into through-beam and diffuse-reflective types.
