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COATING-THICKNESS

GAUGES

R. A. Laaneot-s

UDC 531.717.5.082.74.089.6

In a formerly proposed device for testing electromagnetic thickness gauges [i] the thickness of coating was simulated by means of an air gap. This has been found possible since the magnetic permabi!ity of air and nonmagnetic coatings (varnishes, paints, plastics, etc.) is practically the same (p ~ I). However, the thickness gauge transducer of the device and its air gap meter, a multi-turn MIG indicator with a scale value of 2 pm, were mounted in parallel thus violating the Abbe principle and introducing considerable testing errors. For example, with air gaps of 2-8 pm, the relative error of the thickness gauge reading was 5-20%. Here we describe a device for testing electromagnetic thickness gauges in which the Abbe principle is satisfied. The device is shown schematically in Fig. i. Two angle brackets 2 and 3 are mounted on guide bar i. Bracket 2 holds reference device 8 with base 6 made of the same material as the products whose coating is the bar measured with the thickness gauge under test 9. Base 6 is mounted in place of the measuring tip of reference device 8. This base can be moved by means of lever 7. The measuring transducer 5 of the tested thickness gauge 9 is mounted on bracket 3 by means of sleeve 4. To test the thickness gauge with the aid of the suggested device, the reference device 8 is adjusted so that the surface of base 6 touches the measuring transducer 5. The reference device and the tested instrument are set to read zero in this position. Base 6 is then lowered with the aid of lever 7. The thickness of the resulting gap between the measuring transducer and the base is simultaneously measured by reference device 8 and instrument 9. The error of the tested thickness gauge 9 is found from the difference between these readings. The base 6 can be moved through any distance by means of lever 7 so that electromagnetic thickness gauges can be checked over the entire measuring range at any dial point. The described device can improve the efficiency and accuracy of testing. tion is very simple and so can be constructed in any workshop.

Its construc-

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Fig. 1 LITERATURE CITED !.

V. A. Greshnikov,

I. T. Gubin, and L. A. Minenko,

Izmer. Tekh., No. 5 (1976).

Translated from Izmeritel'naya Tekhnika, No. 2, pp. 27-28, February,

0543-1972/78/2102-0189507.50

1978.

9 1978 Plenum Publishing Corporation

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