This specification is applicable to the calibration of light-scattering laser airborne particle counter (hereinafter referred to as particle counter).
2 Terms
2.1 monodisperse particle
a batch of polystyrene spherical particles with a relative standard deviation of particle diameter ≤ 5%, see Annex A
2.2 particle size
diameter of a certain kind of disperse particles in the air (abbreviated as particle size), is the diameter of a certain monodisperse particle corresponding to the intensity of the scattered light, in units of μm, the particle size measured with particle counter is within (0.1~10)μm
2.3 particle concentration
quantity of disperse particles with diameter not less than the designated diameter exist in the measured air per unit volume within the specified sampling flow rate and sampling time
2.4 error of particle size
error of measurement for percentage of particles in different sizes with particle counter in the aerosol
3 General
Particle counter is the instrument that measures the size of discrete particles and the particle concentration in clean air to determine the cleanliness class of clean room and clean environment. The airborne particle counter may also be used for the measurement of dust content in the air, as well as the performance testing of clean bench and filter.
The particle counter is mainly composed of pneumatic system, optical system, data processing system, etc. The working principle is that the particles in the air have a scattering effect on the incident light, and the intensity of the scattered light is related to the particle size. The air containing airborne particles is sucked from the sampling port of the airborne particle counter, when passing through the light sensitive area, the airborne particles are scattered into the optical pulse signals which are proportional to the particle size under light irradiation, and the signal is accepted by the photosensor and converted into corresponding electric pulse signal which is amplified again, and the number of airborne particles in the sample air per unit volume, that is, the particle concentration, may be known by counting the electric pulse in one testing period.
