How to Choose Laser Dust Sensor and Infrared Dust Sensor

The laser can be focused into a very concentrated parallel beam, and can maintain a small spread angle and high power density over a long distance. Common lasers are generally divided into three categories: solid-state lasers, gas lasers and semiconductor lasers (commonly known as laser LEDs). In the field of instrument laser particle counters, (helium-neon) gas lasers are generally used as light sources. In the field of dust sensors, due to cost constraints, laser LEDs are generally used as light sources.

Jun 30,2022


The laser can be focused into a very concentrated parallel beam, and can maintain a small spread angle and high power density over a long distance. Common lasers are generally divided into three categories: solid-state lasers, gas lasers and semiconductor lasers (commonly known as laser LEDs). In the field of instrument laser particle counters, (helium-neon) gas lasers are generally used as light sources. In the field of dust sensors, due to cost constraints, laser LEDs are generally used as light sources.

Infrared LEDs are light-emitting diodes with emitting wavelengths in the infrared range. The common wavelengths are generally around 850nm to 940nm. They are widely used in medical, security, communication, remote control and sensing fields. Since the emitting wavelength of infrared LED is outside the visible spectrum, with the receiver of a specific spectrum, the influence of ambient light on the received signal can be greatly reduced. Due to the continuous maturity of infrared LED technology in recent years, infrared LEDs have the characteristics of long life, high emission efficiency, good monochromaticity and good directionality. This makes infrared LEDs widely used in the sensor field, especially in the dust sensor industry.

In the current field of dust particle PM2.5 detection, two types of dust sensors are mainly used: infrared dust sensors and laser dust sensors.

Some customers have questions about the difference between them. Winsen Technology will give you a brief introduction from five aspects.

1. Structure and principle

The structure and circuit of the infrared principle dust sensor are relatively simple. The light source is an infrared LED light source, and the air flow into and out are mainly heated by resistor to obtain hot air flow, and a high level is output when particles pass through. The output signal is only PWM model.

The structure and circuit of the laser sensor are relatively complex. The light source is a laser diode. The sampled air is pushed by a fan or blower through a complex designed air duct for detection. When the fine particles in the air enter the area where the laser beam is located, the laser light will be scattered; the scattered light is radiated in 360° of space, we place a photodetector in an appropriate position so that it only receives scattered light. Then a current signal is generated by the photoelectric effect of the photodetector, which can be amplified and processed by the circuit to obtain the concentration of fine particles. The output signal is generally serial output.

2. Price and cost

Infrared dust sensors have been used in the industry for many years, the market price is about 5.4-7.7USD/PC, and the market price of laser dust sensors is 13.8-27.7USD/PC.

The cost gap between the two sensors is mainly because the material cost of the latter adds mechanisms such as laser generators and fans, requires complex circuit structures, and has a high technical requirement.

3. Measurement accuracy

The infrared principle dust sensor can only detect particles above 1um, and the measurement accuracy is insufficient. Because the particle signal scattered by infrared LED light is weak, it only responds to large particles larger than 1um, and only the heating resistor is used to drive the sampling airflow, the sampling number is small, the data calculation is completely handed over to the host computer.

While the laser dust sensor can detect particles above 0.3um. Because of its own high-performance CPU, a large amount of data is collected by fans or blowers, and analyzed by professional particle counting algorithms. In summary, it has more advantages than infrared dust sensors in terms of sampling number, data source and algorithm.

4. Application

Due to the lack of precision, the infrared principle sensor is mainly used for industrial and mining dust. The detection object is large particle size and high concentration dust. The detection level is mg/m3, which cannot accurately measure the concentration of PM2.5.

The laser principle sensor is mainly used in the field of PM2.5 detection to quantify the quality of PM2.5 with precision. It can be used in household (vehicle, handheld) air detectors and air purifiers. In addition, laser principle sensors are also used in Internet of Things data collection, environmental quality detection and other fields.

5. Development trend

Before laser dust sensors entered the domestic field, infrared dust sensors were widely used in air purifiers. However, with the development of the air purifier industry and the mass production of laser dust sensors by some large factories, the cost of laser dust sensors is gradually decreasing. Meanwhile, end customers have higher requirements for accurate air quality measurement. Using laser principle sensors to accurately quantify PM2.5 quality is a recognized trend in the industry.

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