ULTRASONIC WAVE PROPAGATION TIME MEASURING SYSTEM

摘要

A position detecting method and system which eliminate the influence of residual vibration of a piezoelectric or magnetostrictive element, increases the correlation between a received ultrasonic waveform and a model waveform, and are not affected by a reflected wave of an ultrasonic wave signal. A transmitting unit (2) of an ultrasonic wave propagation time measuring system generates an electromagnetic wave signal including a trigger signal indicating transmission timing and an ultrasonic wave driving signal by modulating an ultrasonic wave on the basis of a pseudorandom signal with high autocorrelativity simultaneously with transmission of the electromagnetic wave signal, and transmits an ultrasonic wave signal with a frequency higher than that of the ultrasonic wave driving signal by an ultrasonic wave transmitter (104). A receiving unit (3) detects the electromagnetic wave signal and the ultrasonic wave signal, and includes a data processing circuit (206) which using the ultrasonic wave driving signal as a model waveform, calculates a correlation value between the detected ultrasonic wave signal and the model waveform, detects a main peak value of the calculated correlation value, and calculates the ultrasonic wave propagation time from the detection time point of the electromagnetic wave signal and the detection time point of the main peak value (Fig. 1).