SU1262367A1 - Multichannel device for acoustical-emission check of articles - Google Patents

Abstract

This invention relates to non-destructive testing of products by acoustic emission. The aim of the invention is to increase the reliability of control by reducing the influence of noise by leveling the reference levels of the comparators installed in each channel. The signal in each channel is received by the converter, amplified, fed to one of the inputs of the comparator, and through the switch alternately measured in amplitude. The smallest signal level is then determined, the difference between this level and the levels of each of the channels is measured. Through a digital-to-analog converter, the threshold level of the comparator in each channel is changed by the amount of this difference. The output signals from the comparators are fed to the unit for calculating the coordinates of the acoustic emission sources. 1 il. (ABOUT

Description

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The invention relates to non-destructive testing by the method of acoustic emission and can be used to monitor the developing defects of various products (pressure vessels, boilers, pipelines, etc.) to prevent accidents.

The purpose of the invention is to increase the reliability of control by reducing the influence of noise.

The drawing shows a block diagram of a device for acoustic emission monitoring of products from four channels.

Each channel of a multichannel device for acoustic emission monitoring of products contains a converter 1 -If connected in series, a preamplifier -2, an amplifier and a comparator, the second input of which is connected to the output, an D / S converter S S-. The preamplifier output of each channel is connected to the corresponding information input of the switch 6, the output of which is connected to the input of the amplitude meter 7. The output of the comparator 4 of each channel is connected to the corresponding input of the coordinate calculation unit 8. The output of the amplitude meter 7 is connected to the memory unit 9 connected in series, the smallest amplitude determination unit 10 and the subtraction unit 11, the second input of which is connected to the output of the memory block 9 and the output to the input of the coordinate calculation unit 8. The operation of the switch 6 and the memory block 9 is controlled by the clock generator 12.

The device works as follows.

In the locus of points equidistant from the receiving transducers 1 of several channels of the group, an acoustic emission simulator is installed.

Signals are received at each station by converter 1, converted to electric, amplified by preamplifier 2 (mainly located in the area of the control object), and then by amplifier 3 and fed to comparators 4. When these signals exceed the voltage level at the second input of the comparators 4, it comes from to the coordinate calculation unit 8 a pulse, based on the difference in arrival times from which each channel calculates the coordinates of the source of the acoustic emission signals.

The signals after the preamplifier 2 arrive at the corresponding inputs of the switch 6.

Next, their amplitude is measured, memorized, the channel with the smallest amplitude is found, and the difference in the signals of each channel with this found level is determined by which the comparator threshold of the comparators 4 is changed using 7 amplitude meter, memory block 2, unit 10 for determining the smallest amplitude, block 11 subtraction and digital-to-analog converters 5 -5-.

This leveling of the operation of the channel comparators depending on the amplitudes of the signals makes the dynamic range of the amplitude measurement path constant and sufficiently large. There is no need to regulate periodically

in the process of monitoring the gain of this path, which reduces the noise. This increases the accuracy of determining the coordinates, the accuracy of measuring the amplitude of the signals, and hence the reliability of the control.

Claims (1)

Invention Formula A multichannel device for acoustic emission monitoring of products, containing, in each channel, a serially connected converter, preamplifier, amplifier and comparator, a unit for calculating the coordinates, whose inputs are connected to the outputs of the comparators, in order to increase the control reliability by reducing the influence no noise it is equipped with series-connected clock generator, a switch, the inputs of which are connected to the outputs of preamplifiers, an amplitude meter, a memory unit, the second input of which is connected to the output of the clock generator, the smallest amplitude determining unit and the subtraction unit, the second input of which is connected to the output of the memory unit, and each channel is equipped with a digital-analogue converter connected between the second input the comparator and the outputs of the subtraction unit and the amplitude meter.