Both PM 2.5 and PM 10 are pollutants in the air, which will endanger our health. So when choosing a PM measuring device, you should be careful and serious. Today, I will introduce to you what online PM monitor methods are available for PM 2.5 and PM 10, so that you can know more about how to choose a PM measuring device.
1. Aerodynamic particle size detection method
The aerosol sampling airflow is accelerated by the acceleration nozzle. After the sampling airflow passes through the nozzle, the airflow velocity changes. Particles of different sizes in the airflow will have different accelerations due to inertia, for example, large particle size has large inertia and slow acceleration. As a result, the time to pass the fixed-width detector is different.
The aerodynamic method can directly obtain the particle size concentration distribution of PM10 and PM2.5. The aerodynamic method, which is widely used, is less affected by the shape, refractive index and density of the particles, and is closely related to human health.
2. Laser scattering intensity detection method
The laser scattering intensity detection method is to suck atmospheric aerosol into the instrument by a vacuum pump, and use a laser gas analyzer to detect aerosols of different particle sizes. Aerosols of different particle diameters generate scattering signals of different intensities through the laser detector. Large particles have strong scattering signals, and small particles have weak scattering signals. The signal processor converts the scattering signal into an electric pulse signal. The electric pulse signal intensity of large particles is high, and the electric pulse signal intensity of small particles is low. The number concentration information of different particle diameters is obtained by calculating the strength of the pulse signal. Generally, the detected particle size is 0.3 to 10 microns, or even larger.
3. Electric mobility detection method
The aerosol is sucked into the instrument by the vacuum pump. There is a gradient electric field voltage in the instrument. The charged aerosol undergoes the migration phenomenon in the electric field under the action of the electric field force, moves in a certain direction under the sheath gas, and finally deposits. At a certain point in the electric field. Different parabolic trajectories are formed under the profile of the same charge. Small particles have high electric mobility, and the distance flying in the electric field is short, which will form the short parabolic trajectory. And the electric mobility of large particles is low, so the distance flying in the electric field is long forming the long parabolic trajectory. By adjusting the voltage, particles of different particle sizes can be collected at the same location.
The electric mobility detection method is suitable for detecting nano-scale particles smaller than 1 micron, the smallest to 2.5 nanometers.