1st half time meter, gas concentration measuring device, 1st half time measuring program and 1st half time measuring method

摘要

The present invention aims to improve the measurement accuracy of the first half time of ultrasonic waves. The processor 28 as an arithmetic unit includes a first correlation target signal obtained based on a first upper limit change rate, which is a rate of change of the upper envelope of a direct wave signal, and a first lower limit change rate, which is a rate of change of the lower envelope of a direct wave signal, and one round-trip delayed wave. The correlation target determination unit 32 is configured to obtain a second correlation target signal obtained based on the second upper limit change rate, which is the rate of change of the upper limit envelope of the signal, and the second lower limit change rate, which is the rate of change of the lower limit envelope of the 1 round trip delay signal. In addition, the processor 28 is configured with a correlation processing unit 34 that obtains a correlation value between the signal to which the first correlation target signal and the second correlation target signal are moved on the time axis. The correlation processing unit 34 functions as a first half time measurement unit to obtain a time difference between the first correlation target signal and the second correlation target signal based on the correlation value, and the time at which the ultrasonic wave propagates the concentration measurement space based on the time difference. Have