Working principle and usage precautions of dust particle counter

Particle counter is an instrument used to measure the number and size distribution of particles per unit volume of air in a clean environment. Particle counter is widely used in medicine, electronics, precision machinery, color tube manufacturing, microbiology and other industries to monitor the purification effect and cleanliness level of workbenches, clean rooms and clean workshops of various cleanliness levels to ensure product quality.

The most common particle counters are light scattering (APC) type, which can measure particle sizes from 0.1 to 10 μm. In addition, there are condensation nucleus particle counters (CNC) that can measure smaller particles. This article will introduce light scattering particle counters.

Working principle of dust particle counter

Particles in the air will scatter when exposed to light, a phenomenon called light scattering. Light scattering is related to factors such as particle size, light wavelength, particle refractive index, and particle absorption characteristics. However, in terms of scattered light intensity and particle size, the intensity of particle scattered light increases as the surface area of ​​the particle increases.

Particle Counter Workflow

First, the vacuum pump system allows the gas to be detected to pass through the particle counter laser head at a specified flow rate. The dust particles in the gas will scatter the laser signal in the particle counter, so that the optical sensor in it receives and generates a pulse information number. Secondly, the pulse information number is output and amplified, and then digital signal processing is performed. By comparing it with the standard particle signal, the comparison result is expressed by different parameters. The number of electric pulses corresponds to the number of particles, and the amplitude of the electric pulse corresponds to the size of the particles.

Precautions for using particle counters

1. Do not start the counter when the inlet tube is covered or blocked.

2. The particle counter should be used in a clean environment to prevent damage to the laser sensor.

3. Do not measure mixed gases that may react (such as hydrogen and oxygen). These gases may also explode in the counter. To measure these gases, you need to contact the manufacturer to obtain more information.

4. Do not sample compressed air without high-pressure pressure reducing equipment (such as a high-pressure diffuser). All particle counters are designed to operate at atmospheric pressure.

5. Water, solution or other liquids cannot enter the sensor from the inlet pipe.

6. The particle counter is mainly used to test the clean environment of the purification workshop. When the measuring place has loose particle materials, dust sources, and spray places, it must be kept at least twelve inches away from the inlet pipe to prevent the above particles and liquids from contaminating the sensor and pipeline.

7. When sampling, avoid sampling the gas exhausted from the counter itself or contaminated by the gas discharged from the counter.

8. When connecting an external printer or an external temperature and humidity sensor, you must turn off the counter first; when performing a printing operation, there must be printing paper on the printer, otherwise the print head will be damaged.