Particulate Matter (PM) refers to the solid and liquid particles suspended in air. PM Sensors are used to determine the PM2.5 and PM10 particle concentration in air. Optical PM sensors use light scattering principle to determine PM concentration in air. This application report looks into a single operational amplifier (Opamp) based analog front end (AFE) solution for Particulate Matter (PM) monitoring sensors. This application note discusses how the scattered light by the particles can be converted into an output voltage proportional to the intensity of light incident on the sensor. The voltage output can be processed using various algorithms to determine the concentration and size information.
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Particulate Matter (PM) refers to the solid and liquid particles suspended in air. PM2.5 and PM10 refers to particulate matter having diameter less than 2.5 μm and 10 μm respectively. There are several methods to measure the Particulate Matter (PM) concentration in air based on gravitational, centrifugal and optical concepts.
Optical based PM measurement techniques uses the concept of light scattered or light absorbed by the particles to estimate the size and concentration of the particle as shown in Figure 1-1. Light scattered by a particle depends upon the particle size, particle shape and refractive index of the particle. Apart from these parameters, optical chamber design, light source and detection angle influence the light scattering. Light scattering based PM measurement instruments can be of two types, Photometers and Optical Particle Counters.