| 摘要 |
PURPOSE:To shorten the propagation distance of an ultrasonic wave to 1/2 as long as before and also to reduce an oscillation output to 1/4, and to reduce a cost by installing an ultrasonic wave transmitter in a reference measurement surface right below an ultrasonic wave transmitter-receiver, and switching the driving and received signals of those transmitter and transmitter-receiver by a switching circuit. CONSTITUTION:The ultrasonic wave transmitter 7 is provided right below the ultrasonic wave transmitter-receiver 1 by being embedded in the reference measurement surface 2, and a body 6 to be measured is arranged between the transmitter-receiver 1 and transmitter 7. Then, an ultrasonic wave 9 sent by the transmitter-receiver 1 is reflected by the body 6 and inputted to the transmitter-receiver 1, which converts it into an electric signal. When the distance between the transmitter-receiver and body 1 is 3, the distance between the surface of the body 6 and reference surface 2 is 4, and the distance between the transmitter-receiver 1 and the reference surface 2 which is measured by the transmitter 7 and transmitter-receivers 1 in the reference measurement surface is 5, the propagation distance of the ultrasonic wave is 1/2 and the oscillation output is 1/4 if the distances 3 and 4 are equal to each other, thereby eliminating the need for a complex, expensive high-output circuit.
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