Diffuse Photoelectric Sensor


What is a diffuse photoelectric sensor?

diffuse photoelectric sensor

A diffuse photoelectric sensor is also called diffuse-reflective sensor, is a type of optical sensor that uses light to detect objects. It works by emitting a beam of light and then detecting the scattered light that bounces off a detected object. This type of sensor contains two components: an emitter and a receiver. The emitter houses the light source while the receiver houses the light detector. When an object is present, the light reflects back to the receiver, and this triggers an output signal that can be used to activate or deactivate a process.

The characteristics of the diffuse reflection photoelectric switch

The characteristics of the diffuse reflection photoelectric switch include fast response time, high resolution, high precision, , ease of  heat dissipation, lead-free materials, and long service life. It complies with RoHS standards and is a new generation of green and environmentally-friendly energy sources. 

  1. This type of switch has a long sensing distance, and because it is non-contact, it does not damage the sensing object and is unaffected by the object being sensed. Unlike proximity switches, the photoelectric switch is not limited by the material of the object being detected, as it uses reflection and light transmittance methods to detect the object.
  2. Due to its lack of mechanical parts, the response time is quick, allowing it to detect high-speed moving objects.
  3. However, the lens can be easily affected by organic dust and other contaminants, which cause the light to scatter or become obstructed. Therefore, it is necessary to apply appropriate protective devices when using it in environments with high levels of water, steam, dust, and other substances.
  4. While it is not affected by general lighting, strong light sources such as direct exposure to sunlight can cause misoperation or damage to the sensing device.

diffuse photoeletric sensor applications

Diffuse photoelectric sensors are widely used in a variety of applications:

  1. Packaging and Material Handling – Diffuse photoelectric sensors can be used to counting the quantity of a objects on conveyor belts, packaging machines or filling lines. They are used to ensure that no empty containers or improperly packaged products make it through the production line.

  2. Automotive Industry – In the automotive industry, diffuse photoelectric sensors are used to detect the presence of vehicles in parking garages, car washes or traffic light systems. They are also used in collision avoidance systems to detect nearby objects.

  3. Food and Beverage Industry – Diffuse photoelectric sensors are used to detect the presence of objects in food processing lines, conveyor systems or automated packaging systems. They are commonly used in the food and beverage industry because of their resistance to dust, dirt, and moisture.

diffuse photoeletric sensor Wiring

Proximity sensor wiring diagram

The diffuse photoelectri sensor is also a kind of proximity sensor, even its working principle is different as the inductive or capacitive sensor, but the output of them are same, it can be NPN+NO, NPN+NC, PNP+NC, PNP+NO etc., so their wiring is same, you can see this article to get the knowledge of the wiring.

diffuse photoelectric sensor troubleshooting

If you’re experiencing issues with your diffuse photoelectric sensor, here are some troubleshooting steps to follow:

  1. Check the power supply: as the working voltages of a photoelectric sensor can be DC10-30V or AC90-260V, make sure that the voltage is suitable for your diffuse photoelectrical sensor.
  2. Clean the lens: Dirt and dust build-up can interfere with sensor performance, so cleaning the sensor with a soft, dry cloth may solve the problem.

  3. Check the output: If the output is PNP, you need to connect the load to the sensor signal wire and another end shall be wired to a negative pole, NPN wiring is just converse.
  4. Try to talk with its manufacturer to get a professional advice.


the difference between a diffuse and retroreflective sensor

Diffuse sensor detects the presence of an object using reflected light, while the retro reflective sensor needs a reflector to get back the emitting light. 

Property Diffuse-reflective Sensor Retro-reflective Sensor
Reflection methodLight reflected by object Interrupted light beam
Need for dedicated reflectorNoYes
Easiness of mounting Easier without the need for a dedicated reflector Requires mounting of a dedicated reflector
Effect of physical conditions Performance affected by color and texture of object Less affected by color and angle of the object
Functionality Object acts as the reflector Dedicate reflector is required
Dead-zone distance None Visible at extremely close distances
Sensing distance Several centimeters to several meters Several centimeters to several meters
Wiring complexityWiring complexity Wiring complexity
Cost LowerModerate to higher
Application examples Object detection, assembly line quality control, packaging controlDetecting transparent objects (like glass), detecting small objects in machinery, etc.


In conclusion, diffuse photoelectric sensors are used in almost every industry to improve automation, safety, and process efficiency. Whatever the application, diffuse photoelectric sensors are a reliable and fast tool for detecting the presence or absence of objects in automated systems.


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