| 摘要 |
The invention relates to a means and an apparatus for the determination of the mass concentration of suspended particles in a gaseous medium. By generating and transmitting siniusoidal sound waves with one or more predetermined frequencies through a gaseous medium and, at a certain distance from the transmitter, receiving and converting the sound waves to electrical signals, the sound velocity change of the sound signal or signals is measured. By producing and processing this information, a direct measure of the aerosol concentration in the medium can be obtained. The arrangement according to the invention consists mainly of a measuring chamber (5), an electronic unit (2), a transmitter (3) and a receiver (4). The electronic unit (2) consists in its turn mainly of first and second frequency channels (7, 8), a phase measuring unit (6), a delay circuit (17) and a digital display arrangement (9).
|
