Measurement error reducing in the ultrasound time-pulse systems

Abstract

Ultrasound wave propagation in bounded media results in change of the echo-pulse shape, therefore the use of traditional method of determining of the propagation time of the ultrasound pulse based on use of threshold device (comparator) gives a large error of measurement. To reduce this error the new methods of the determining of echo-pulse propagation time are proposed in this paper. The first method is the method based on the use of two comparators, the second one is the method based on second-order polynomial approximation of the echo-pulse envelope. Analysis showed that the steeper the rising edge of the echo-pulse envelope, the less the error of determining of the pulse start time. The more the difference between comparator thresholds the less the error of determining of the pulse start time. Application of the method of two comparators gives two times systematic error reducing. Minimal sampling of input signal is determined for the method based on echo-pulse envelope. Dependence of the error at start echo-pulse determining on adjacent samples amplitude ratio is obtained. Application of echo-pulse envelope gives three times systematic error reducing.