Gas concentration and flow rate sensor

摘要

A gas vapor sensor indicates the relative concentrations and flow rate of a gas mixture. Acoustic noise is generated within a closed chamber by the gas mixture flowing therethrough or by ambient noise sources. The chamber has a fundamental resonant frequency which varies with the vapor concentration. Acoustic frequency components of the noise corresponding to the resonant frequency of the chamber are sharply reinforced and dominate the acoustic spectrum within the chamber. The spectrum is detected and frequency filtered by a pair of dissimilar parallel filters to produce two attenuated outputs. The difference between the attenuated outputs indicates the resonant frequency and is a measure of the vapor concentration. The strength of the acoustic spectrum together with the measured vapor concentration indicates the flow rate of the mixture.