Three monitoring methods are commonly used by Particle Monitors:
Light scattering method: the basic principle of this method is that the light emitted by a laser light source projects on the measured particles, causing light scattering, and receives scattered light signals through photoelectric conversion elements in a certain direction. This includes the number and intensity of scattered light. The number of scattered light detected represents the number of particles, and the light intensity signal represents the size of particles. The particle number can be obtained directly by this method, but it can be converted into mass concentration after statistical calculation.
Ray method: when a ray appears on the medium, particles collide with electrons in the medium, lose energy and are absorbed, but under low energy conditions, it is independent of particle size, composition, color and dispersion state, and depends on the quality of the medium. The atmosphere gas is sucked into the sampling tube by the sampling head, discharged through the filter paper, and the particles are stacked on the filter paper. When the ray passes through the filter paper with particles, the energy is attenuated. The mass concentration of particles can be calculated by measuring the ray energy before and after attenuation.
Micro-vibration balance method: the micro-vibration balance method is to use a vibrating hollow cone tube in the mass sensor and installs a replaceable filter membrane at its vibrating end. The vibration frequency depends on the characteristics and quality of the cone tube. When the sampling gas flow passes through the filter, in which the particles are deposited on the filter, and the change of the filter quality causes the change of the vibration frequency, the mass of the particles deposited on the filter is calculated through the change of the vibration frequency, and the mass concentration of the particles in this time period is calculated according to the flow rate, on-site ambient temperature and air pressure.