National Institute of Advanced Industrial Science and Technology

Hideki Toda

Tatsu Kobayakawa

Hiroshi Yamada

Sachiko Saito

Sachiko Saitou

A gas concentration measurement instrument comprises: ultrasonic wave transmitting means for transmitting an ultrasonic wave according to an ultrasonic wave generation signal composed of a group of rectangular pulse waves; ultrasonic wave receiving means for converting the ultrasonic wave transmitted through the gas in the measurement region into an electric signal to use it as an ultrasonic wave reception signal; and gas concentration measuring means for measuring the signal output time when the ultrasonic wave generation signal is outputted, generating an envelope processing signal by subjecting the ultrasonic wave reception signal to an envelope extracting processing, measuring the threshold fall time when the envelope processing signal decreases below a predetermined threshold after exceeding the threshold, and measuring the difference between the threshold fall time and the signal output time as change in the gas concentration.

Gas concentration measurement instrument and gas concentration measurement method

A gas-concentration measuring apparatus for measuring the concentration variation of gas residing in a target region. The gas-concentration measuring apparatus comprises an ultrasound-transmitter adapted to transmit an ultrasound 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, and further adapted to output the ultrasound-generating signal. An ultrasound-receiver adapted to receive the ultrasound wave passed through the gas residing in the target region, and further adapted to convert the received ultrasound into an electrical signal serving as a received ultrasound signal is provided. A gas-concentration determiner adapted to input the ultrasound-generating signal and the received ultrasound wave signal into the operational amplifier to generate an amplified transmitting-side chopping wave and an amplified receiving-side chopping wave is further provided. The gas-concentration determiner is further adapted to compare the transmitting-side and receiving-side chopping waves independently with corresponding given threshold voltages to detect a first pair of time points when the respective chopping waves become equal to or greater than the corresponding given threshold voltages or to detect a second pair of time points when the respective chopping waves become equal to or less than the corresponding given threshold voltages. The gas-concentration determiner is further adapted to determine the concentration variation in the gas based on the pair of time points.

Growing community of inventors

Ibaraki, Japan

Hideki Toda