SYSTEM FOR TRANSMITTING AND RECEIVING ULTRASONIC PULSE

PURPOSE:To remote the effect of an interference wave by the averaging effect of propagation time difference, by selectively outputting either one of positive and negative polarity transmission signals and setting the point of time when a receiving signal arrived a predetermined change point as the arrival time of an ultrasonic signal. CONSTITUTION:A transmission signal output means 10 is constituted of a pulse generation circuit 11, a drive circuit 12, a transmitting and amplifying circuit 13 consisting of transistors 13A, 13B and a transmission terminal 14 connected to ultrasonic transmitter receivers 2, 3 through a transmission and reception change-over circuit 4. This ultrasonic signal output means 10 selectively outputs either one of positive and negative polarity ultrasonic signals taking the relation of mutually inverse polarity according to preset sequence or random sequence and allows said signal to propagate through the medium to be measured of a flow pipe 1 to selectively output the same to ultrasonic signal detection means 20 and the point of time, when the ultrasonic signal arrived a predetermined change point, is set as the arrival time of the ultrasonic time regardless of the polarity of the ultrasonic wave propagated through the medium to be measured.