Practical Guide: Master Photoelectric Sensors for Through-beam, Diffuse Reflection, and Retroreflective Applications
What is a Photoelectric Sensor?
What is a Photoelectric Sensor?
Photoelectric sensors detect the presence or absence of objects through the amount of light reflected back to the receiver, based on the degree of light blocking (light shielding), enabling non-contact detection.
As shown in the figure, the transmitter on the left emits light, and when the receiver on the right receives sufficient light (light intensity), it is judged as ON; otherwise, it is OFF.
Common Photoelectric Sensor Types and Application Examples
1. Through-beam Type:
The emitter and receiver are separate. This type of sensor detects whether the transmitted light is blocked or interrupted, making it unaffected by the object's shape, color, or angle.
Application Example:
In food packaging production lines, many food products are sealed in transparent packaging. A through-beam sensor can detect whether the food is sealed inside the transparent package.
2. Retro-reflective Type:
This type of sensor integrates both the emitter and receiver into a single unit and uses a reflector to bounce the light back to the receiver. Detection is based on whether the reflected light is blocked or interrupted. Compared to through-beam sensors, retro-reflective sensors are easier to wire and more cost-effective.
Application Example:
Retro-reflective photoelectric sensors can be used to detect the presence or absence of objects on production lines. Wiring is required on one side, and a reflector is installed on the opposite side.
3. Diffuse-reflective Type:
In this type, the emitter and receiver are integrated into one unit. The emitted light is reflected by the object and detected by the receiver. However, the sensor's performance can be affected by the object's shape, color, or angle.
Application Example:
During metal processing, diffuse-reflective sensors can confirm the presence or absence of holes in the metal. If the light is projected into a hole, no signal is reflected back to the sensor; if there is no hole, the light is reflected back, making it easy to detect the hole.
4. Background Suppression Type:
These sensors use PSD/C-MOS photoelectric elements and detect objects based on distance rather than light intensity. This effectively reduces the influence of an object's color on detection, which is common in diffuse-reflective sensors. Background suppression sensors typically have a shorter detection range.
Application Example:
This type of sensor is often used to detect the presence of objects in trays. By measuring the height difference, it can reliably detect the presence or absence of items, even when the color of the objects or tray changes, without requiring adjustments.
Recommended Photoelectric Sensors
Photoelectric Sensors Through-beam Sensors GM18 Series
The GM18 series photoelectric sensor is a cylindrical through-beam sensor, featuring a copper-nickel plated housing and using invisible infrared light (880 nm) as the light source. It offers detection ranges of 5 meters and 15 meters, with an operating voltage range of DC 10 - 30 V and output options of NPN/PNP. The sensor is connected via a 2-meter PVC cable. The GM18 series is capable of operating stably in high-temperature environments up to 55°C, making it suitable for use in automation equipment operating in temperatures ranging from 0°C to 55°C. To ensure product quality, DADISICK's GM18 photoelectric sensors undergo a rigorous seven-step inspection process, including high and low-temperature shock, load aging, performance testing, full-body testing, insulation resistance testing, wire bending and tensile tests, and surge testing, ensuring each sensor's stability and reliability.
Related Photoelectric Sensors
Detection range: 30-300mm
Detection range: 50-500mm
Detection range: 80-1000mm
Material: Nickel-copper alloy
Connection type: 3pin/4pin with 2M cable
Detection range: 2-50mm
Detection range: 2000mm
Casing material: SUS316L
Connection type: Wire lead type (standard wire length 2m)
Detection range: 2000 mm, 3000 mm
Material: Nickel-copper alloy
Connection type: 3pin/4pin with 2M cable
Maximum detection distance: 2 - 150 mm
Stable detection distance: 3 - 120 mm
Power supply voltage: 12 - 24 V DC
Switch output: NPN/PNP
Connection type: Cable, 4 cores, 2 m
