SU1548746A1 - Eddy current device for nondestructive inspection - Google Patents

Abstract

The invention relates to non-destructive testing and can be used to measure the thickness of dielectric coatings on electrically conductive bases. Measurement of the thickness of dielectric coatings is achieved by processing the signals of the inductor coils of the eddy current transducer, which alter their signals in the same way as the base parameters are varied. When an eddy current transducer interacts with a controlled product, the impedances of inductance coils 4 and 5 vary in different ways as the dielectric coating thickness of the product changes. If the ratio R ₁ F ₁ = R ₂ F _{2 is} observed, where R ₁ and R ₂ are the radii of coils 4 and 5, respectively

F ₁ and F ₂ are the frequencies of the high and low frequency generators 1 and 2, respectively, the variation of the specific electrical conductivity and magnetic permeability can be suppressed by further processing carried out by the information processing unit. 1 il.

Description

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The invention relates to non-destructive testing and can be used to measure the thickness of dielectric coatings on electrically conductive bases.

The purpose of the invention, measuring the thickness of dielectric coatings, is achieved by using an information processing unit, which eliminates the influence of the variation of the electrical conductivity and magnetic permeability of the product on the combination of signals from the eddy current transducer inductance lithitation and unequal radii.

The drawing shows the block diagram of the eddy current device,

The eddy current device contains a source of harmonic voltages of fairies and lower frequencies, consisting of generators 1 and 2, the highest and lowest parts, respectively, switch 3, their current converter, consisting of coaxial coils 4 and 5, inductive-1st, placed in the same plane, an information processing unit consisting of series-connected switches 6, amplifier 7, amplitude detector 8, amplifier 9, amplitudes of detector 10 and divider 11, for example, keny, and a low-frequency filter 12 connected between amp output If there is a good detector 8 and the second input of the voltage generator 11, the indicator 13, connected to the output of the voltage divider 11, and the generator 14 clock pulses. The signal inputs of the switch 6 are connected to the outputs of the vortex converter, and the control

the input of the switch b is connected to the generator output 14 clock pulses. The device works as follows.

The coils 4 and 5 of the inductance alternately connect to alternators 1 and 2, respectively, and with the switch 6, the output voltage of the eddy current transducer from coils 4 and 5 alternately enters the input of the series-connected amplifier 7 and amplitude detector 8 When placing the end of a eddy current transducer on the surface of a controlled product, the impedances of inductance coils 4 and 5 are different due to the difference in their radii when the thickness of the dielectric coating is changed.

As a result, the voltage amplitude at the input of amplifier 7 depends on the inductance connected to it, and the output of the amplitude detector 8 is a constant (average) voltage level and an alternating voltage, the frequency of which is determined by the oscillator 14 clock pulses. The alternating voltage at the output of the amplitude detector 8 is amplified by the amplifier 9, detected by the amplitude detector 10 and fed to the first input of the voltage divider 11, and the constant (average) voltage level after filtering (to reduce the voltage ripple, frequency which is determined by the frequency of the generator 14 clock pulses) in the low-pass filter G2 is fed to the second input of the voltage divider 12.

At the output of divider i 2, a signal is extracted, the value of which is unambiguously related to the thickness of the dielectric coating (the distance to the product) and practically does not depend on changes in the specific electrical conductivity and magnetic permeability of the base material over wide limits. This signal is recorded by indicator 13. The minimum effect of the base material on the indicator readings is provided by observing the following relationship between the radii R1, R of the inductors and the frequencies f of the generators I and 2: R, f g

This follows from the fact that at the chosen ratio the generalized parameters of both inductors are the same.

Claims (1)

Invention Formula An eddy current device for non-destructive testing, containing a source of high and low frequency harmonic voltages, a eddy current converter consisting of two coaxial inductors, a switch, inclusions between the outputs of a source of harmonic voltages and inductors of the eddy current converter, a clock pulse generator connected by an output to a controller. to the input of the switch, an information processing unit connected signal inputs to the outputs of the vortex converter and a control input to the output of the clock generator, and an indicator connected to the output of the information processing unit, characterized in that, to measure the thickness of dielectric coatings, the inductors of the eddy current converter are located in one plane, the information processing unit is made in the form of serially connected second switch; body, amplitude detector, second amplifier, second amplitude detector and voltage divider, as well as a low-pass filter connected between the output of the first amplitude detector and the second input of the voltage divider, the output of which is the output of the information processing unit, the control input of the second switch and its signal inputs are the control input and signal inputs of the information processing unit.