Particulate matter sensors are used to detect the particulate matter concentration in the air. Particulate matter refers to solid particles or liquid droplets with a diameter of less than 100 micrometers, including naturally occurring dust, smoke, and haze, as well as industrial dust and exhaust emissions generated by human activities. Particulate matter pollution causes serious harm to human health and the environment, so the monitoring and control of particulate matter concentration is of great significance.

There are many types of particulate matter sensors, which can be divided into the following categories based on their working principles:

Optical sensors are currently the most widely used particulate matter sensors. Their working principle is to use light scattering or absorption to detect particulate matter. Laser scattering sensors are the most common type of optical sensors, working by using a laser beam to irradiate particulate matter in the air and measuring the scattering intensity on the particle surface. Light absorption sensors work by using the absorption of light beams on the surface of particles. Photoresist sensors work by detecting changes in light resistance caused by the absorption or scattering of light by particulate matter.

Electrochemical sensors are based on the principle of electrochemical reactions. Their working principle is to use the reaction of particles on the electrode surface to generate electrical signals. Ion-selective electrode sensors are the most common type of electrochemical sensors, using ions produced by the reaction of particles on the electrode surface. Electrochemical impedance sensors work by utilizing resistance changes caused by reactions of particles on the electrode surface.

Thermal sensors are based on the principle of heat conduction. Their working principle is to use the influence of particulate matter on heat conduction. Thermistor sensors are the most common type of thermal sensors, utilizing the temperature influence of particles on the thermistor. Thermocouple sensors work by utilizing the influence of particles on the thermoelectric potential of the thermocouple.

Ion sensors are based on the principle of ion migration. Their working principle is to use the influence of particulate matter on ion migration. Electrostatic induction sensors are the most common type of ion sensors, using the influence of particles on the output signal of the electrostatic inductor. Ion-sensitive crystal sensors work by utilizing the influence of particles on the vibration frequency of the ion-sensitive crystal.

The choice of particulate matter sensor should be based on its application scenario and requirements. For example, for application scenarios requiring high precision and stability, optical or electrochemical sensors should be chosen; for application scenarios requiring low cost and portability, thermal or ion sensors should be selected.