SU1613941A1 - Method of checking parameter of electric conducting layer - Google Patents

Abstract

This invention relates to instrumentation technology. The aim of the invention is to improve the accuracy of the control. The eddy current transducer is placed in the control zone, the frequency of the transducer excitation current is changed in the range that permits the penetration of the electromagnetic field to a depth from a few fractions to a value equal to or greater than the layer thickness, the amplitude of the signal inserted into the transducer is measured, and frequency function of the eddy current converter. Before control, the transducer is placed above the sample with a thickness much greater than the depth of penetration of the electromagnetic field into it and plotting the amplitude versus frequency over the entire range of possible variations of the electrical conductivity of the monitored layer, and then comparing the amplitude of the measured signal with the amplitude of the signal on the plotted dependencies at equal frequencies and measurements the frequency when they match. 2 hp ff, 2 ill.

Description

The invention relates to instrumentation engineering and can be used in non-destructive, quality control of products (eddy, ultrasonic, and other methods).

The invention is aimed at increasing the control accuracy by increasing the reliability of determining the informative parameter — the drive excitation current frequency, as the intersection point of two amplitude-frequency dependencies, as well as expanding the range of values of the parameter being monitored by expanding the range of possible intersection of these dependencies.

FIG. 1 shows a block diagram of a variant of the device for carrying out the proposed method; monitoring the parameter of the electrically conductive layer; in fig. 2 — Dependences of the amplitude A of the signal of the converter system — electric wire 1nd non-magnetic layer with a thickness much greater than the penetration depth of the electric field (curve 6) into it and amplitude Ag of the signal of the converter system — electrically conductive nonmagnetic

WITH

layer (curve 7) from the change in the frequency of the signal td

I A device for implementing the method contains a variable frequency generator 1 of adjustable frequency, an eddy current transducer 2, an measuring unit 3 and a processing unit 4 connected at the first input to the output output, a second input to the frequency output of the measuring unit 3, and on the third input - to the output of the storage unit 5, Connected at the input to the frequency OUTPUT of the measuring unit 3. The output of the processing unit 4 is the output of the device as a whole.

The method is based on the presence of a countable set of points of coincidence (intersection) of the amplitude-frequency dependences of the converter system — the control layer and the converter system — an electrically conductive non-magnetic product with a thickness of t-co.

The method is implemented as follows.

The eddy current transducer 2 is placed in the control zone. With the help of generator 1, the frequency of the excitation current of converter 2 is regulated in the range that ensures the penetration of the electromagnetic field to a depth from several distances of the thickness of the layer to € equal to or greater than the thickness of the layer. After that, the output signal of the converter 2 is fed to the input of the measuring unit 3. With the help of block 3, the amplitude A and the frequency CO (Fig. 2, curve 7) of the signal introduced into the converter 2 are measured with a test layer. Then, the voltages proportional to the measured parameters of the Ag and CO signal from the outputs of the measuring unit 3 are fed to the corresponding inputs of the processing unit 4. Before control (experimental or calculated), the dependence (Fig. 2, curve .6) of the amplitude of the signal AJ introduced into the converter 2 by an electrically conductive nonmagnetic layer with a thickness much greater than the depth of penetration of the electromagnetic field, on the frequency tx) is determined. The obtained dependence is introduced into the storage unit 5, the input of which is simultaneously the frequency output of the measuring unit and the output is the third input of the processing unit 4. The output of block 3 is affected by a voltage proportional to the amplitude of signal A. In block 4, the processing at the measured frequency of the signal of converter 2 is compared, the amplitude A is obtained from the resulting dependence and the measured amplitude A and the condition of the frequency and signal of the converter is fixed. In this case, the output of block 4 is affected by a voltage proportional to the value of the monitored parameter of the electrically conductive layer.

Additional improvement in the accuracy of the control parameters of the layer is achieved

 the fact that from the set of 4 frequency values recorded in the block 60 (t. O, - C, etc. in Fig. 2), its minimum value is chosen, i.e. in t. O (A, SOO) in the vicinity of which the difference () of amplitudes is greater than, for example, in t. C.

Introducing amplitude comparison operations on frequency dependencies of a transducer system — an electrically conductive layer; a different, much greater penetration of electromagnetic field into it; and a transducer system — an electrically conductive layer of finite thickness, and measuring the frequency values at their coincidence points, judged by About the parameter of the monitored layer, it allows to significantly increase the accuracy of the control. At the same time an additional increase in accuracy. Control is provided

5 by selecting the minimum value from the set of frequency values at which the amplitude-frequency dependencies coincide.

five

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Claims (3)

Formula shade shadow 1, The method of controlling the parameter of the electrically conductive layer, which consists in placing the eddy-current transducer in the control zone, changes the frequency of the transducer current in the range that permits the penetration of the electromagnetic field to a depth from several fractions of thickness to a depth equal to or greater than the thickness of the layer, The amplitude of the signal of the converter is used, and the frequency of the excitation current is used as an informative parameter, characterized in that, in order to increase the control accuracy, WCE tolshrnoy with much greater depth of penetration into it of electromagnetic FIELDS obtain the dependence of the amplitude of the transducer signal on the frequency of the excitation current, compare the amplitude of the signal of the transducer located in the control zone with the amplitude of the signal on the resulting relationship at equal frequencies and use the informative frequency when the amplitudes coincide. 2. The method according to p. 1, TL and .4 AU - Y and with the fact that, in order to expand the range of values of the monitored parameter of the layer, the dependence of the signal amplitude of the converter on the frequency of the excitation current is obtained on samples with conductivity within its possible variation under control. 3. The method according to paragraphs. 1 and 2, that is, from the set of frequencies corresponding to the coinciding amplitude values, the minimum   .g