Laser dust sensor: Aside from obscure physical terms, compared with ordinary visible light, laser has the characteristics of high coherence, strong directivity, good monochromaticity and high power density. For example, the light generated by the laser light source is like a chorus, and everyone's voice is the same tone and the rhythm is neat; The light produced by ordinary visible light sources is like the noise in a teahouse, which is chattering and chaotic.
Therefore, the laser can be focused into a very concentrated parallel beam, and a small diffusion angle and a high power density can be maintained over a long distance. Common lasers are generally divided into three categories: solid-state lasers, gas lasers and semiconductor lasers (commonly known as laser light-emitting diodes). In the field of instrument-level laser particle counter, (He-Ne) gas laser is generally used as the light source.
Difference between them: 1. The structure and circuit of PM2.5 dust sensor based on infrared principle are relatively simple. Its light source is infrared LED light source, and the air inlet and outlet mainly rely on resistance heating to obtain hot air flow, and the particles output high level when passing through. The output signal is only in PWM mode.
2. The structure and circuit of the laser PM2.5 sensor are relatively complex. Its light source is a laser diode. The sampling air is driven by a fan or blower and tested through a complicated air duct. When fine particles in the air enter the area where the laser beam is located, it will scatter the laser beam; Scattered light radiates at 360 degrees in space. We put a photodetector in a proper position to receive only scattered light, and then generate a current signal through the photoelectric effect of the photodetector. After circuit amplification and processing, the concentration of fine particles can be obtained. The output signal is usually a serial output.
3. Price and cost Dust sensors based on infrared principle have been used in the industry for many years, and the market price is about tens of yuan. The price of laser dust sensor is around 200 yuan. The cost difference between the two is mainly due to the fact that the latter adds mechanisms such as laser generator and fan to the material cost, which requires complex circuit structure and high technical threshold.
4. Measurement accuracy The infrared principle dust sensor can only detect particles above 1 micron, 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 1 micron, and only uses heating resistor to drive the sampling airflow, so the sampling times are few, and the data calculation is completely handed over to the upper computer. The laser sensor can detect particles above 0.3 micron. Because of its own high-performance CPU, a large amount of data is collected by fans or blowers and analyzed by professional particle counting algorithm; To sum up, it has more advantages than infrared dust sensor in sampling quantity, data source and algorithm.
5. Due to the lack of accuracy, the infrared principle sensor is mainly used for industrial and mining dust, and the detection object is large particles and high-concentration dust, and the detection level is mg/m3, so it is impossible to accurately measure the concentration of PM2.5. The laser principle sensor is mainly used in the field of PM2.5 detection, which can accurately quantify the quality of PM2.5 and can be embedded in household (vehicle-mounted, handheld) air detectors and air purifiers. In addition, the laser principle sensor is also used in the fields of data acquisition and environmental quality detection in the Internet of Things.
6. Development Trend Before the laser principle sensor entered the civil field, infrared principle sensors were widely used in air purifiers. However, with the development of air purification industry, the cost of laser principle sensor is gradually decreasing, and the requirements of end customers for accurate measurement of air quality are getting higher and higher. It is a recognized trend in the industry to accurately quantify the quality of PM2.5 by using laser principle sensors, and some air purifiers have adopted laser principle sensors.
7. Infrared dust sensor and PM2.5 sensor have their own advantages, and there is no exact statement about which PM2.5 detector is better. The appropriate detector should be selected according to the customer's requirements (such as cost requirements, accuracy, signal output, application site, related particles to be detected, etc.).
CW-76S dust sensor (dust detector) is a high-tech product which integrates aerodynamics, digital signal processing and photoelectricity independently developed by Shenzhen Sainawei. It is mainly used to detect the dust mass concentration (PM value) in the atmosphere, and is suitable for construction sites, urban grid monitoring, mobile monitoring and other fields and occasions. It is the core module of air quality detection system.