SU905620A1 - Dielectric coating thickness gauge - Google Patents

Description

I

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

Dielectric coating thickness gauges are known that contain a parametric eddy current transducer with a ferrite core included in the resonator circuit of the auto-oscillator, a compensation unit, an amplifier, a dial gauge and a power supply unit. They allow measurement of the thickness of dielectric coatings on a non-magnetic electrically conductive base. Reducing the interfering effect of the udipy electrical conductivity of the base is achieved by selecting a sufficiently high operating frequency i.

However, for accurate measurements, it is necessary to calibrate the instrument for each base material.

The closest in technical essence to the present invention are dielectric coating thickness gauges containing series-connected

an auto-oscillator, an overhead eddy current transducer, a phase-sensitive detector, a reference voltage to which is supplied from the auto-generator through a phase shifter, and an indicator 2. However, these thickness gauges do not provide sufficient accuracy and do not allow measuring the thickness of dielectric coatings on both non-magnetic and ferromagnetic basis simultaneously.

The purpose of the invention is to increase the accuracy of measuring the thickness of dielectric coatings, regardless of the value of the specific electrical conductivity and magnetic permeability of the base material.

Claims (2)

This goal is achieved by the fact that the thickness gauge is equipped with an amplitude detector and adder, the input of the amplitude detector is connected to the output of the eddy current transducer, and the output is connected to one of the inputs of the adder, the other input of which is connected to the output of the phase-sensitive detector, and the output to the indicator. FIG. 1 hodographs of the applied nagf of the laid on eddy converter, depending on the specific electrical conductivity and relative magnetic permeability (U /, characterized by the generalized parameter piq // -Y - R ijjTZ C / И, where and is the radius of the eddy-transformer; is the steep frequency of the excitation current; fj. is the magnetic constant and from the distance V between the windings of the vyusra current transducer and the electrically conductive surface characterized by the generalized parameter II 2ii (R; Fig. 2 is a block diagram of the device. FIG. 1 species but that the hodographs of the applied voltage of the overlaid eddy converter, depending on the general parameter (bd / l / x, for a ferromagnetic material, are close to arcs of circles whose centers lie on the axis Yivy, and axis ;, they all intersect at the same angle For non-matrix materials, hit on these hodographs is achieved by selecting a sufficiently high frequency of the excitation current. It is very important that the radii of these circles depend only on the generalized parameter H or, in other words, on the thickness of the dielectric coatings. At the same time, the order of a raschgus with a fault of not more than 4% can be found from the inflator .5-RgO + A, where Re0 (4 is the active component of the apparent voltage of the eddy current generator; A is the amplitude of the applied voltage. The device (Fig. 2) a) contains atophore 1, an overhead eddy current transducer 2, a phase-sensitive detector 3, a reference voltage to which is supplied from an auto-oscillator through a phase shifter 4, an output detector 5, an adder b and an indicator 7. The auto-oscillator 1 feeds a sinusoidal overhead eddy-current converter 2. The input voltage from the output of the eddy current transducer 2 is simultaneously applied to the inputs of the phase-sensitive 3 and amplitude 5. The vector voltage of the phase-sensing detector 1. is set using a phase-shifter 4 with the exciter current of the transducer 2. Transmission coefficient the amplitude detector 5 is 1.45-1.55 times less than that of the phase-sensitive detector 3. The constant voltages from the outputs of both detectors are fed to the inputs of the adder 6 and, having developed, from its output are fed to the indicator 7. The proposed stroystvo za ene ey known devices which make it possible to measure the dielectric coatings toshii1gu or only on the basis of non-magnetic or only on a ferromagnetic base. At the same time, when switching from one base material to another, no additional settings of the device are required. The invention The thickness gauge of dielectric coatings containing a series-connected auto-oscillator, an invoice eddy current transducer, a phase-sensing detector, a reference voltage supplied to the auto-oscillator through a phase shifter, and an indicator that, in order to improve the accuracy of measuring the thickness of the dielectric coatings independently of the values of electrical conductivity and magnetic permeability of the base material, it is equipped with an amplitude detector and adder, the amplitude input th detector connected to the output of the eddy current transducer and an output coupled to one of the adder inputs, DRU1YUY ksggorogo input connected to the output of phase-sensitive detector, and an output - to an indicator. Sources of information taken into account in the examination 1. Dorofeev A. L. and others. Induction thickness gauge, M., Energie, 1978, p. 142-146. 2. Devices for non-destructive control of materials and products. Directory. Pope rep. at. V. Klyuev, Vol. 2, M., Mechanical Engineering, 1976, p. 143-1-16 (prototype).