SU1746293A1 - Method of determination of time of propagation of acoustic vibrations in medium - Google Patents

Abstract

The invention relates to non-destructive testing of building materials, mainly soils, and can be used to determine their physico-mechanical properties. The aim of the invention is to improve the accuracy when measuring in environments with high elastic wave attenuation. The method, which compares the parameters of the received signal with given constant electric level, the times at which the value of the first and second half-waves modulo the magnitude exceeds the constant level are additionally measured, and the correction time they are calculated taking into account these measured times 1 or

Description

(L

WITH

The invention relates to non-destructive testing of building materials, mainly soils, and can be used in determining their physical and mechanical properties.

A known method of adjusting the origin when measuring the propagation time of acoustic waves in a material is that they emit and receive an acoustic signal, convert it to electric, establish two levels of electrical signal and determine the origin of reception of an acoustic signal by reducing the time the front reaches an electrical signal & t level at the time of correction.

The closest in technical essence is a method for determining the origin when measuring the propagation time of acoustic waves in a material, which consists in the fact that they emit and receive an acoustic signal, convert it into an electrical one, establish two levels of an electrical signal that are equal in magnitude but opposite in sign and the correction time is defined as half the time of the change in the decay of the signal from the first to the second level

Use this method to determine the time of entry. A fading acoustic signal leads to an error associated with that. that the amplitudes of the first and second half-waves are not the same, therefore, half the time interval for the change in the signal decay from the first to the second level does not coincide with the point of transition of this signal through zero

4 O Yu Yu

s

The purpose of the invention is to improve the accuracy in measurements in environments with a large attenuation of elastic waves.

The drawing shows the plot of the signal received in the process of acoustic control.

The reference point is the moment of emission of the signal, U is the value of the constant electric level, t is the time between the moment of emission and reception, i.e. intersections of the first half-wave constant level, ti is the time between the moments of time at which the signal values during the fall of the first half-wave and the rise of the second half-wave are equal to the value of the constant level, ta is the time during which the value of the first half-wave exceeds the constant level; t4 is the time during which the value of the second half-wave modulo exceeds a constant level.

The essence of the invention is that they emit and receive an acoustic signal, convert it into an electrical one, set a constant electrical level, measure the time of arrival of the signal at a time instant corresponding to the equality of the values of the first half-wave signal and constant level, measure the time ti between the points in time at which the signal values during the fall of the first half-wave and the rise of the second half-wave are equal to the constant level, and, in contrast to the known one, the times ta and t4 are also measured, at which ache- of the first and second half-wave modulo

BUT

exceeds the value of a constant level. Time ta correction calculated by the formula

t4-t3 + 2tl

four

And the time t of propagation of acoustic oscillations in the medium is defined as

,

Claims (1)

Claims The method of determining the time of propagation of acoustic oscillations in a medium, which consists in emitting and receiving an acoustic signal, converting it into an electrical one, setting a constant electrical level, measuring the time of arrival of the signal according to the moment of time corresponding to the equality of the first half-wave signal and constant level, measure the time ti between the points in time at which the signal values during the fall of the first half-wave and the rise of the second half-wave are equal to the value of the constant level, the correction time t2 is calculated, and the propagation time of acoustic oscillations is determined taking into account the correction time, characterized in that, in order to improve accuracy when measuring in media with a large elastic wave attenuation, the times ta and t4 are also measured, at which the first and the second half-wave modulo exceeds a constant level, and the correction time t2 is calculated by the formula t2 (tHs + 2ti) / 4.