What are the factors that affect the accuracy of the measurement value of the coating thickness gauge?
1. Magnetic properties of the base metal: The thickness measurement by the magnetic method is affected by the magnetic change of the base metal (in practical applications, the magnetic change of low carbon steel can be considered slight), in order to avoid the influence of heat treatment and cold working factors, it should be used and tested Calibrate the instrument with a standard sheet with the same properties as the base metal of the piece; it can also be calibrated with a test piece to be coated.
2. Base metal thickness: Every instrument has a critical thickness of base metal. Above this thickness, the measurement is not affected by the thickness of the base metal. See attached table 1 for the critical thickness value of this instrument.
3. Electrical properties of the base metal: the electrical conductivity of the base metal has an impact on the measurement, and the electrical conductivity of the base metal is related to its material composition and heat treatment method. The instrument is calibrated using a standard sheet having the same properties as the base metal of the test piece.
4. Edge effect, the coating thickness gauge is sensitive to the sudden change of the surface shape of the test piece. It is therefore unreliable to measure near the edge or inside corners of the test piece.
5. Curvature: The curvature of the test piece affects the measurement. This effect always increases significantly with decreasing radius of curvature. Therefore, measurements on the surface of curved test pieces are not reliable.
6. Deformation of the test piece: the probe will deform the soft covering layer test piece, so reliable data can be measured on these test pieces.
7. Surface roughness: The surface roughness of the base metal and the covering layer has an impact on the measurement. The greater the roughness, the greater the impact. Rough surface will cause systematic error and accidental error, and the number of measurements should be increased at different positions for each measurement to overcome this accidental error. If the base metal is rough, it is also necessary to take several positions on the uncoated base metal test piece with similar roughness to calibrate the zero point of the instrument; or use a solution that does not corrode the base metal to dissolve and remove the covering layer, and then calibrate the instrument. zero.
8. Attached substances: The instrument is sensitive to those attached substances that prevent the close contact between the probe and the surface of the covering layer. Therefore, the attached substances must be removed to ensure that the probe of the instrument is in direct contact with the surface of the test piece.
9. The orientation of the measuring head of the coating thickness gauge: the placement of the measuring head has an influence on the measurement. During the measurement, the probe should be kept perpendicular to the surface of the sample.
10. Probe pressure: The pressure exerted by the probe on the test piece will affect the measurement reading, so keep the pressure constant.
11. Magnetic field: The strong magnetic field generated by various electrical equipment around will seriously interfere with the magnetic thickness measurement work.
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