Patent ID: 6823715
Filing Date: 2004-11-30
Classification: G01N

Abstract:
A gas-concentration measuring apparatus for measuring the concentration variation of gas residing in a target region, said gas-concentration measuring apparatus comprising:an ultrasound-transmitter adapted to transmit an ultrasound wave in response to an ultrasound-generating signal having a rate of voltage change equal to or greater than a slew rate of an operational amplifier, said ultrasound wave being transmitted through the gas residing in the target region; an ultrasound-receiver adapted to receive the ultrasound wave after passing through said gas residing in said target region, and further adapted to convert said received ultrasound wave into an electrical signal serving as a received ultrasound signal; and a gas-concentration determiner adapted to input said ultrasound-generating signal and said received ultrasound signal into said operational amplifier to generate an amplified transmitting-side chopping wave and an amplified receiving-side chopping waver; wherein the gas-concentration determiner is further adapted to compare said transmitting-side and receiving-side chopping waves independently with corresponding given threshold voltages to detect a first pair of time points when said respective chopping waves become equal to or greater than said corresponding given threshold voltages or to detect a second pair of time points when said respective chopping waves become equal to or less than said corresponding given threshold voltages, and wherein the gas-concentration determiner is further adapted to determine the concentration variation in said gas based on said pair of time points.