Patent ID: 6892566
Filing Date: 2005-05-17
Classification: G01N

Abstract:
1. A gas concentration sensor comprising: a measurement chamber for measuring the concentration of a specific gas component in a gas under measurement; an inflow path for allowing inflow of the gas under measurement to the measurement chamber and an outflow path for allowing outflow of the gas under measurement from the measurement chamber; a reflection wall disposed on one end surface of the measurement chamber and adapted to reflect an acoustic wave; and an acoustic wave transmitting-receiving element having, on the other end surface of the measurement chamber, which surface opposes the reflection wall, a transmitting-receiving surface adapted to transmit an acoustic wave toward the reflection wall and receive the acoustic wave reflected from the reflection wall, whereby the concentration of the specific gas component in the gas under measurement is detected on the basis of a propagation time between transmission of the acoustic wave and reception of the reflected acoustic wave, wherein the sensor is adapted such that, in use, the transmitting-receiving surface faces downward; a peripheral portion of the reflection wall includes a recess receded away from the transmitting-receiving surface; and the outflow path or the inflow path communicates with the recess at a predetermined position lower than a front surface of the reflection wall.