RU1797697C - Method of determining zero time reference in measuring propagation time of acoustic waves in materials - Google Patents

Abstract

The invention relates to acoustic measurements and can be used to control the stress state of a rock mass. An object of the invention is to increase accuracy in measuring the propagation time of acoustic waves. The goal is achieved by determining the reference point, taking into account the attenuation of acoustic waves in the material. When implementing the method, the first period of the transmitted signals is recorded. The maximum signal values of the half-cycles of the received signal are determined, and the coefficient M used to select the threshold signal value is determined from their ratio. The tij t2 corresponding to two threshold values are recorded in the decay portion of the received signal, and the reference point is determined by the half-sum of the measured times. 1 ill. ate with

Description

The invention relates to acoustic measurements and can be used to control the stress state of a rock mass.

A known method for determining the reference point when measuring the propagation time of acoustic waves in a medium is that the received acoustic signal is converted into an electric signal, two levels of the electrical signal are set and the reference time between the signals is determined by decreasing the time that the front of the signal reaches the first level by the correction time .

Closest to the invention is a known method for determining the reference point when measuring the propagation time of acoustic waves in a material, which consists in emitting an acoustic signal into the material, receiving the first period of past vibrations, recording the time t2 and the signal reaching two threshold values of different signs by the decay portion of the received signal, which is used to determine the origin.

The disadvantage of this method is the low accuracy of measurements in an inhomogeneous medium with noticeable attenuation in amplitude and frequency, for example, in rocks during geophysical measurements and acoustic control methods.

An object of the invention is to increase accuracy in measuring the propagation time of acoustic waves.

This goal is achieved by the fact that in the method of determining the reference point when measuring the burden of propagation of sharks | O XI O

Yu

VI

with

waves in the material, which consists in emitting an acoustic signal into the material, receiving the first period of the past vibrations, recording the time the signal reaches two threshold values of different signs in the decay portion of the received signal, determine the maximum half-periods of the received signal, and the threshold threshold level is negative signal values are selected by the threshold level of the positive signal value multiplied by the ratio of the maximum values of the signal half-periods, and the reference point is determined by half-sum times corresponding to thresholds of the received signal.

The drawing shows a timing diagram of a received signal.

The method for determining the reference point when measuring the propagation time of acoustic waves is carried out as follows.

Acoustic vibrations are emitted into the material and take the first period of the past vibrations. The maximum half-lives of the received UMI and UM2 signal are recorded. Determine the ratio of the maximum signal values

.. um2

M ": -: -, characterizing the attenuation of aku

static wave. The threshold value Um of the positive half-signal of the signal and Una MUni of the negative half-period of the signal are selected. Time ti is recorded and

t2 corresponding to the threshold values of Urn and Uri2 in the decay portion of received signal 5

0

5

Q

5

la, and the reference point is determined by the half-sum of the measured times:

. t1 + t2

1

The use of the method of determining the reference point when measuring the propagation time of acoustic signals makes it possible to increase the accuracy of acoustic control methods in real media in which attenuation in amplitude and frequency is noticeable during geophysical studies, monitoring the stress state of a rock mass, the stability of structures, etc. d.

Claims (1)

The claims The method for determining the reference point when measuring the propagation time of acoustic waves in a material, which consists in emitting an acoustic signal into the material, receiving the first period of transmitted vibrations, recording the time it takes for the signal to reach two threshold values of different signs in the decay area of the received signal, which are used to determining a reference point, characterized in that in order to improve accuracy, determine the maximum values of the half-periods of the received signal, the threshold level of a negative value with The needle is selected by the threshold level of the positive signal value multiplied by the ratio of the maximum values of the signal half-periods, and the reference point is determined by half the time corresponding to the threshold values of the received signal. S f m “h m  Bc Ј