Dust concentration detector is a key equipment for environmental monitoring and industrial safety, and its core technologies mainly include light scattering method, beta ray absorption method, and electrostatic induction method. The three principles are different and applicable to different scenarios.
1、 Light scattering method
Principle: Laser or infrared light irradiates suspended particles, and the sensor receives the scattered light intensity from the particles. The scattered light intensity is positively correlated with the concentration of particulate matter, and can be converted to mass concentration through calibration.
Advantages:
Extremely fast response (in seconds), suitable for real-time monitoring and alarm.
Compact structure, low cost, and relatively simple maintenance.
Can distinguish different particle size channels (such as PM2.5, PM10).
Disadvantages:
The measurement results are significantly affected by the material, color, and shape of particulate matter, and need to be calibrated for specific dust.
In high humidity environments, water mist can cause interference.
Usually used as a relative measurement, the absolute accuracy is lower than that of the beta ray method.
Typical applications: indoor air quality monitoring, rapid industrial process alarm, portable detector.
2、 β - ray absorption method
Principle: The attenuation that occurs when low-energy beta rays (such as C-14 source) penetrate the dust collected on the filter membrane. The degree of attenuation is strictly proportional to the quality of the collected dust, thus directly calculating the mass concentration.
Advantages:
Direct measurement of quality is one of the benchmark methods with high accuracy and data.
Almost unaffected by the physical and chemical properties of particles, the results are reliable.
Long term continuous sampling analysis can be conducted.
Disadvantages:
Slow response speed (usually one data per hour), unable to provide real-time alerts.
The equipment is expensive, bulky, and requires regular replacement of the radiation source and filter membrane, making operation and maintenance complex.
Involving low-dose radioactive sources, special permits and management are required.
Typical applications: National control stations for environmental air quality, scientific research calibration, regulatory arbitration measurement.
3、 Electrostatic induction method
Principle: Based on the static charge carried by dust particles due to friction during movement. The probe measures the electrostatic current or potential fluctuations generated by dust passing through the sensing area, and its signal is related to the dust concentration and velocity.
Advantages:
No optical components, extremely sturdy and durable, suitable for harsh industrial environments such as high temperature, high pressure, and high humidity (such as smoke ducts and conveying pipelines).
Fast response speed, simple equipment, easy installation and maintenance.
Suitable for large particles and high concentration ranges.
Disadvantages:
The measurement results strongly depend on the charging characteristics and flow rate of dust, and require strict calibration.
Relatively low sensitivity, not suitable for monitoring low concentrations or clean environments.
The accuracy is average, mostly for trend monitoring or alarm.
Typical applications: leakage monitoring of industrial bag filter, monitoring of powder conveying process, monitoring of flue dust emission trend.
Summary and Comparison
Pursuing high precision in law, choose the beta ray method.
Pursuing real-time performance, cost-effectiveness, and wide application, choose the light scattering method.
Used for monitoring and trend alarm in harsh industrial processes, using the static inductance method.
In practical applications, a combination mode of "real-time monitoring by light scattering method+regular calibration by beta ray method" is often used to balance speed and accuracy.