Pressure sensor and its application

Abstract

A pressure sensor includes a detection unit 1 having capacities C1 and C2 varied by a predetermined external action, a reference detection 2 unvaried by the predetermined external action, a first oscillator 31 and 32 for generating a detection frequency signal according to the capacities C1 and C2 of the detection unit 1, a second oscillator 33 for producing a reference frequency signal according to the capacity of the reference unit 2, and measuring circuits 34, 35, 36 and 37 for measuring the number of the periods of the detection frequency signal within a predetermined period of the reference frequency signal to produce a measured signal. The sensor can minimize a detection error, and directly convert the change of capacity into a pulse signal (digital signal) without convertion into an analog, so that the circuit construction be simplified and realized at a reduced cost. The gas meter G includes a gas pressure introducing path 155 formed on a wall of a measuring chamber 154 within its meter body 150, and the pressure sensor S secured on a wall of the measuring chamber 154 through a sealing means the pressure receiving portion of which communicates with the gas pressure introducing path 155, whereby any specific gas introducing tube to introduce the gas into the pressure sensor S is not required and the problems of sealing at an insertion portion of the specific gas introducing tube toward the measuring chamber 156 are resolved.