Dual-wavelength optical sensor for measuring the surface area concentration and the volume concentration of aerosols

The surface area concentration and the volume concentration of aerosols can be used to detect fire smoke. However, existing optical sensors with a single wavelength source cannot measure these two concentrations accurately. In this paper, we design a sensor to measure these two concentrations with dual wavelength sources, based on the phenomenon that the surface area concentration and the volume concentration of aerosols are proportional to the scattering intensity of the different wavelength incident lights. The prototype sensor is tested by monodisperse aerosols with particle sizes ranging from 200 nm to 2000 nm. The standard measurement deviations of the surface area concentration, volume concentration and Sauter mean diameter are 11.6%, 21.9% and 9.4%, respectively, which are better than the results of sensors with a single wavelength source. Moreover, the Sauter mean diameter of fire smokes measured by our sensor are consistent with calibration instruments, which is helpful to resist false alarm in fire detection. With simple mechanical structure and high accuracy, this sensor is promising in fire detection and atmosphere environment monitoring.