How does Atmotube PM sensor work?

The PM sensor uses a laser scattering principle, which works by using a laser to radiate suspending particles in the air. Then scattering light is collected in a certain degree, and finally the curve of scattering light change with time is obtained. In the end, equivalent particle diameter and the number of particles with different diameter per unit volume can be calculated by microprocessor based on MIE theory.

PM light scattering
  1. Fan draws in air through inlet
  2. Air passes through the laser where the light reflected off the particles is captured by the photodiode.
  3. The photodiode passes information to the photoelectric converter. The photoelectric converter processes the signal from the particles into density.
  4. Signal is transmitted to micro control unit where a proprietary algorithm processes the data and supplies outputs for the density of the particulate (μg/m³).

Functional diagram of the sensor’s operation (figure courtesy of ©Honeywell).