Label：PM2.5, Sensor, Infrared, Laser
Jan 7, 2021540
PM is the abbreviation for particulate matter, suspended in the air. Among them, those with a diameter less than or equal to 2.5 microns are called PM2.5, or fine particles. Compared with coarser particles, fine particles are richer in toxic and harmful substances, and can stay in the atmosphere for a longer time, have a longer transportation distance, and have a greater impact on the atmospheric environment and human health.
In the particulate matter PM2.5 monitoring equipment, there are mainly two types of sensors: infrared PM2.5 sensor and laser PM2.5 sensor.
Infrared PM2.5 sensor is mainly used for industrial and mining dust due to insufficient accuracy. The detection object is large particle size and high concentration dust. The detection level is mg/m3. It cannot accurately measure the concentration of PM2.5. It can only detect the degree of dust pollution.
Later, the laser PM2.5 sensor was invented, which can accurately measure the concentration of PM2.5. It is mainly used in the field of PM2.5 detection and can be embedded in household (car, hand-held) air detectors and air purifiers. The new laser PM2.5 sensor is based on quantitative measurement, can detect 0.3μm particles, can accurately measure the value of PM1.0, PM2.5, PM10, with high accuracy.
So what are the differences between the two?
1. Structural Principle
The structure and circuit of the infrared PM2.5 sensor are relatively simple. The light source is an infrared LED light source. The air inlet and outlet are mainly heated by resistance to obtain hot air flow. When particles pass through, reflection occurs after contact with the LED light source. The photosensitive detector receives reflected light of different intensities and then undergoes amplification processing, and get the test result after calculation.
The structure and circuit of the laser PM2.5 sensor are relatively complicated. The light source is a laser diode. The sampled air is pushed by a fan or blower and passed through a complicatedly designed air duct for detection.
The structure and circuit of the laser PM2.5 sensor are relatively complicated. The light source is a laser diode. The sampled air is pushed by a fan or blower and passed through a complicatedly designed air duct for detection. When fine particles in the air enter the area where the laser beam is located, the laser will be scattered; scattered light is radiated at 360° in space, and a photodetector is placed in an appropriate position to receive the scattered light, and then generated by the photoelectric effect of the photodetector After the current signal is amplified and processed by the operational amplifier circuit, the concentration of fine particles can be obtained. The output signal can be in a variety of ways such as serial port, I2C, and PWM.
2. Measurement Accuracy and Life
The infrared PM2.5 sensor can only detect particles above 1um, and the measurement accuracy is insufficient. Because the infrared LED light scattering particle signal is weak, it only responds to the large particles larger than 1um, and only the heating resistor is used to push the sampling airflow, the number of samples is small, and the data calculation is completely handed over to the host computer.
The laser PM2.5 sensor can detect particles above 0.3um. Because it comes with a high-performance MCU, uses a fan or blower to collect a large amount of data, and analyzes it through a professional particle counting algorithm, it has more advantages than the infrared PM2.5 sensor in terms of sampling method, data accuracy, and algorithm processing.
3. Price and Cost
The cost of infrared PM2.5 sensor is generally between 20 and 50 yuan due to its simple structure.
The laser PM2.5 sensor has a relatively complex structure, and the market price is between 90-180 yuan. Because of the addition of laser generators and fans and the need for complex circuit structures, the technical threshold is higher, so the price is more expensive.
4. Development Trend
Before laser PM2.5 sensors entered the civilian field, many instruments for monitoring PM2.5 used infrared PM2.5 sensors. However, with the development of the sensor industry and the mass production of laser PM2.5 sensors by some major manufacturers, the cost of laser PM2.5 sensors is gradually decreasing.