Measuring chamber for photo-acoustical sensors

A measuring chamber for photo-acoustical sensors for the continuous measurement of radiation-absorbing substances, in particular of radiation-absorbing particles, in gaseous samples includes at least one entry and at least one exit for the samples, a tube section with microphone that allows for the flow-through of the sample in longitudinal direction, and at least one entry and exit point for a laser beam that is aligned with the tube section, and whereby these entry and exit points are both arranged at a distance from the measuring tube by at least one chamber with a cross-sectional area that is expanded relative to the tube section. To prevent soiling of the windows at the points of entry of the radiation into the cell and to slow down the deposition of the particles of the measured aerosol, whereby long-term, high-sensitivity operation of the measuring cell is possible, two entries are envisioned at two ends of the tube section that are opposite relative to each other and at least one exit that is arranged at a location which is centered between the entries.