How are dust particle counters classified? What is their working principle?

    Dust particle counters are devices specially used in clean rooms to detect the particle size and distribution of dust particles in the air. They have been developed from microscopes and have gone through the process of microscopes, sedimentation tubes, sedimentation instruments, centrifugal sedimentation instruments, particle counters, laser particle counters, and PCS nano-laser air particle counters. Laser air particle counters have become equipment in many industries for many years because of their advantages such as fast detection speed, wide dynamic distribution, and freedom from human influence.
 

 

Classification standards for dust particle counting

1. According to the detection principle: Light scattering detection (white light, laser), microscope detection, weighing method detection, DMA method detection (particle size analyzer), inertial method detection, diffusion method detection, condensation nucleus detection (CNC), etc.

2. By flow rate: Small flow rate 0.1cfm (2.83L/min) Large flow rate 2cfm (50L/min-100L/min).

3. By shape and volume: Portable, handheld, online.

4. By test channel: Single channel (only one particle size is measured);dual channel (two particle sizes are tested);multi-channel (multiple particle sizes are tested).

5. Others: Application fields of laser dust particle counter

Particles in the air will scatter under the irradiation of light, which is called light scattering. Light scattering is related to factors such as particle size, light wavelength, particle refractive index and particle absorption characteristics of light. However, as far as the intensity of scattered light and the size of air particles are concerned, there is a basic rule that the intensity of scattered light from particles increases with the increase of the surface area of the particles. In this way, the size of the particles can be inferred by measuring the intensity of scattered light. This is the basic working principle of the light scattering particle counter.

In fact, the intensity of scattered light generated by each particle is weak, which is a very small light pulse. It is necessary to convert the light pulse into an electrical pulse with a larger signal amplitude through the amplification of the photoelectric converter, and then further amplify and identify it through the electronic circuit to complete the counting of a large number of electrical pulses. At this time, the number of electrical pulses corresponds to the number of particles, and the amplitude of the electrical pulses corresponds to the size of the particles.

How does the dust particle counter work?

    The light from the light source is focused into the measuring cavity by lens group 1. When each particle in the air passes through the measuring cavity quickly, it will scatter the incident light once, forming a light pulse signal. This light signal is sent to the light detector through lens group 2, and is proportionally converted into an electrical pulse signal. After amplification and screening by the electronic circuit of the instrument, the required signal is picked out and displayed through the counting system.