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How to calibrate the coating thickness gauge
Jan 11, 2019

How to calibrate the coating thickness gauge

 

For accurate measurements, the instrument should be calibrated at the measurement site.

 

1. Calibration standard (including foil and substrate)

 

A foil of known thickness or a sample of known thickness of the cover layer can be used as a calibration standard. Referred to as a standard film.

 

a) Calibration foil

 

For magnetic methods, "foil" refers to a non-magnetic metal or non-metallic foil or gasket. For the eddy current method, a plastic foil is usually used. "Foil" facilitates calibration on curved surfaces and is more suitable than standard sheets with overlays.

 

b) Standard film with overlay

 

A cover layer of a known thickness which is uniform and firmly bonded to the substrate is used as a standard sheet. For magnetic methods, the cover layer is non-magnetic. For eddy current methods, the cover layer is non-conductive.

 

2. Matrix

 

a) For magnetic methods, the magnetic properties and surface roughness of the standard sheet base metal should be similar to the magnetic and surface roughness of the base metal of the part to be tested. For the eddy current method, the electrical properties of the standard sheet base metal should be similar to the electrical properties of the base metal of the part to be tested. To confirm the suitability of the standard sheet, the base metal of the standard sheet can be compared to the measured reading on the base metal of the part to be tested.

 

b) If the thickness of the metal substrate of the part to be tested does not exceed the critical thickness specified in Table 1, the following two methods can be used for calibration:

 

1) calibrating on a metal standard sheet having the same thickness as the metal substrate of the member to be tested;

 

2) A standard metal sheet or test piece of a metal of sufficient thickness and of similar electrical properties is used, but the bi shall have no gap between the base metal and the gasket metal. For the test pieces with the cover on both sides, the pad method cannot be used.

 

c) If the curvature of the coating to be tested has reached a level that cannot be calibrated on the plane, the curvature of the standard sheet with the overlay or the curvature of the base metal placed under the calibration foil should be the same as the curvature of the specimen.

 

Let's talk about the following, how to calibrate the coating thickness gauge

 

The coating thickness gauge uses calibration methods for three measurements: zero calibration, two-point calibration, and calibration on the sandblasted surface. The two-point calibration method is divided into a test piece method and a second test piece method. There is also a basic calibration for the probe.


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