METHOD FOR PHOTO ACOUSTIC MEASUREMENT OF FOREIGN SUBSTANCES IN GASES

摘要

A process for the photoacoustic measurement of foreign matter in gases, in particular of air pollutants in air or exhaust gases, comprising the irradiation of the carrier gas with modulated light, and thus modulated heating of the gas, as well as the detection of the induced due to this modulated heating of acoustic emission, wherein the vectorial components of the ermittierten sound, preferably the amplitude and phase, are determined. In order to allow the correct amount of determination even at high background signal due to contamination of the measuring apparatus, the acoustic emission is detected both an impurity-free carrier gas as well as for the laden with impurities carrier gas, and is a vector quantity of the amount of foreign substances Duch a weighted subtraction of the signal determined for the fremstofffreie carrier gas from the signal for the laden carrier gas with impurities.