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Coating Thickness Gauge Calibration Points
Sep 14, 2018

Coating Thickness Gauge Calibration Points

Let's talk about the following small series, the focus of the coating thickness gauge calibration

1. Correct calibration is critical to accurate measurements. For  calibration, a sample similar to the object being measured will be  used, ie, both the standard and the measured object should have the same  shape and geometry. Basically, the standard samples of more measuring objects match and the measurement results will be more accurate.

2.  Determine the following properties of the calibration sample and the  object to be measured: - radius of curvature of the surface - substrate  material (such as magnetic permeability, conductance; in an ideal  manner, the standard sample and the measurement object should be the  same material) --Substrate thickness -- the size of the measurement area

3. Make sure the calibration point, sensor tip and calibration template are clean before starting the calibration. Remove any deposits such as grease, metal shavings, etc. if necessary. Any impurities can affect the calibration and cause instability in the calibration.

4. Make sure to always find the same calibration position, especially for small parts and for angular measurements. Measuring brackets are recommended for small parts.

5. Keep away from strong magnetic fields during the calibration process.

6. More calibration standards can be matched to the expected thickness to make calibration and measurement more accurate.

7.  According to the electromagnetic induction method, the thickness of the  non-ferrous metal coating on the steel or iron substrate is measured,  and multi-point correction is required. The thickness standard sample must be made of the same metal as the object to be measured later.

8. If calibration foils are used, make sure they are placed in the planar position of the substrate material. The air gap under the foil must be avoided as this will result in an unstable reading. If it is a curved aluminum foil, make sure they are placed on the substrate as shown below.

9. Precision thickness standards must be handled with care. Any wear and tear of the thickness standard will be reflected in the wrong calibration value. Do not fold the calibration foil. Any buckling will result in an air gap under the film, resulting in an unstable reading. Keep the thickness standard clean. Any grease, oil, dust or other deposits must be avoided. The  deposit of aluminum foil will be considered as a thickness and will  result in a measurement error of the same value as the thickness of the  deposit. Give you a rough idea: a fingerprint deposit is enough to cause an additional thickness error of a few microns.

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.