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What is the difference between the laser PM2.5 sensor and the infrared sensor

Update: 2021-06-15 10:12 Source: LUFTMY Reading: ↻ News

PM is short for "particulate matter", which is suspended in the air and has a diameter of 2.5 micrometers or less, known as PM2.5, or fine particulate matter.Compared with larger particles, fine particles contain more toxic and harmful substances, and can stay in the atmosphere for a longer time, transport distance is further, the impact on the atmospheric environment and human health is greater, is the cause of black lung and haze weather is the main culprit.


Among the equipment for detecting PM2.5 particles, there are mainly two kinds of sensors selected: one is the infrared PM2.5 sensor, the other is the laser PM2.5 sensor.


Infrared principle of PM2.5 sensors due to the precision is less than the laser, so it is mainly used for detection of mining dust, object detection for large particle size, high concentration of dust, detection level is mg/m3, unable to accurately measure the concentration of PM2.5, can only detect the dust pollution degree, of course early air purifier is using the principle of the sensor, measurement results are for reference only,Low accuracy, generally used to judge the degree of dust pollution grade.These are early infrared PM2.5 sensors, and Lufmai's infrared PM2.5 sensor can accurately measure fine particulate matter of 0.3-10 microns, so it is used more in the field of air purification equipment.

Luftmy LD09 Laser PM2.5 Dust Sensor Model


Later, the birth of laser-type PM2.5 sensor can accurately measure PM2.5 concentration, which is mainly used in PM2.5 detection field and can be embedded in home fields, such as vehicle purification equipment, hand-held air detector, air purifier and air conditioner. The new laser-type PM2.5 sensor is based on quantitative measurement and can detect particles with particle size as small as 0.1μm.Can accurately measure the value of PM1.0, PM2.5, PM10, and the measurement accuracy is high.


So what's the difference between the two?


1. Structure principle

Infrared principle PM2.5 sensor structure and circuit is relatively simple.The light source is infrared LED light source, and the air inlet and outlet are mainly heated by resistance to obtain hot air flow. When particles pass through, the reflection phenomenon occurs after contact with the LED light source. The photosensitive detector receives the reflected light of different intensities, and then obtains the detection results after amplification treatment and calculation.

Luftmy LD12 Laser PM2.5 Dust Sensor Model

However, the structure and circuit of the laser PM2.5 sensor are relatively complex.The light source is a laser diode.The sampled air is pushed through a fan or blower, through a complex design of air ducts, for testing.When fine particles in the air enter the area where the laser beam is located, the laser will be scattered;Scattered light radiates in 360° of space. A photodetector is placed at an appropriate position to receive the scattered light, and then the current signal is generated through the photoelectric effect of the photodetector. After amplification and processing by the opp amplifier circuit, the concentration value of fine particles can be obtained.The output signal can be serial port, UART, PWM and other ways.


2, measurement accuracy and life

Infrared principle PM2.5 sensor can only detect particles above 0.3 micron, the measurement accuracy is weak.Because the particle signal of infrared LED light scattering is weak, it only responds to large particles larger than 0.3μm, and it only uses heating resistance to push the sampling airflow, so the number of samples is small, and the data calculation is completely left to the upper computer.


The laser-based PM2.5 sensor can detect particles above 0.1μm.Because of its own high-performance MCU, the use of fans or blowers to collect a large number of data, through professional particle count algorithm analysis, so in the sampling method, data accuracy, algorithm processing and other aspects are more advantages than the infrared PM2.5 sensor.


3. Price and Cost

Infrared principle PM2.5 sensor because of its simple structure so the price is generally between 20-50 yuan.

And laser principle PM2.5 sensor due to the relatively complex structure, the market price between 50-100 yuan.Due to the addition of laser generator, fan and other mechanisms and the need for complex circuit structure, the technical threshold is higher, so the price is slightly higher.


4. Development trend

Before laser-based PM2.5 sensors entered the civil field, many PM2.5 monitoring instruments used infrared based PM2.5 sensors.But with the development of the sensor industry, and manufacturers have realized the mass production of laser principle PM2.5 sensor, and the price of laser principle PM2.5 sensor is also gradually reduced, the future has the potential to replace the infrared PM2.5 sensor.

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