SU122879A1 - Method for measuring coating thickness - Google Patents

Description

Measures for measuring the thickness of coatings by means of devices containing an inductive sensor and a high-frequency generator measuring the thickness of the coating by voltage variation are known.

A distinctive feature of the proposed method is that in order to simultaneously measure two parameters, for example, the thickness of the coating and the interlayer or the thickness of the coating and its conductivity, the frequency is additionally measured and controlled parameters are determined from the values of frequency and voltage; The determination of the latter is carried out on the basis of the previously constructed curves of the experimental dependences of voltage and frequency on the variation of these parameters.

FIG. Figure 1 shows the frequency and voltage curves of a high-frequency generator; in fig. 2 is a schematic diagram of an apparatus for carrying out the described method; in fig. 3 - curves obtained through this device.

Below, as an example, a method is described which makes it possible to measure the thickness of nickel coatings and the copper layer without destroying the product. This method is based on the fact that the change in the frequency and voltage of the generator, in the resonant circuit of which a measuring sensor is included (a coil on a ferrite core), depends on the thickness of the coating and the layer on the product being tested. This dependence is associated with the occurrence of eddy currents on the surface. Eddy currents affect the electrical properties of the sensor, and a change in the latter causes a change in the frequency and voltage of the generator.

FIG. 1 shows the curve O of the variation of the frequency F and the voltage of the generator at zero thickness of the interlayer as a function of the change in the thickness of the nickel coating from 0 to the thickness of the greater penetration depth of the electromagnetic field created by the sensor; , 10 m, and

No. 122879-2 -

15 m. A device whose diagram is shown in FIG. 2 consists mainly of a generator, a resonant circuit sensitive to changes in the frequency of the generator, an instrument / measuring the voltage of the generator, and a recording change in the frequency of the last device 2. With this device, the curves shown in FIG. 3. These curves are as follows. The indications of the instruments Vi and 1/2 were determined for interlayers with a thickness of 0 m, 10 m, 20 m, 30 m and 40 m with a nickel coating of ohm, 10 m, 20 m and 30 m thick. The corresponding points were connected by curves. In this case, the bold curves show the location of points for the case when the thickness of the nickel coating changes at a certain thickness of the copper interlayer. The thickness measurement of the nickel and copper layer is carried out in the following sequence. A measuring sensor is installed on the monitored product with a double-layer coating. The readings of the instruments / and 2 are counted and the resulting point is marked on the coordinate grid.

The location of this point indicates the corresponding thickness of the nickel coating and interlayer & ki.

Subject invention

The method of measuring coating thickness by means of an inductive sensor and a high-frequency generator measuring the thickness of the coating by voltage variation, characterized in that, in order to simultaneously measure two parameters, such as coating thickness and interlayer or coating thickness and its conductivity, the frequency and by determining the values of frequency and voltage, the controlled parameters are determined on the basis of previously constructed experimental dependences of voltage and frequency on the variation of these parameters.

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