Regulations to Be Complied With When Using Coating Thickness Gauges
Regulations to be followed when using instruments
Characteristics of the base metal
For magnetic methods, the magnetic properties and surface roughness of the base metal of the standard piece should be similar to those of the base metal of the specimen.
For the eddy current method, the electrical properties of the standard substrate metal should be similar to those of the specimen substrate metal.
B Base metal thickness
Check if the thickness of the base metal exceeds the critical thickness. If not, one of the methods in 3.3 can be used for calibration.
C-edge effect
Measurements should not be taken at sudden changes close to the specimen, such as edges, holes, and internal corners.
D curvature
It should not be measured on the curved surface of the specimen.
E Reading frequency
Due to the fact that each reading of the instrument is not exactly the same, it is necessary to take several readings within each measurement area. The local differences in the thickness of the covering layer also require multiple measurements within any given area, especially during surface roughening.
F Surface cleanliness
Before measurement, any adhering substances such as dust, grease, and corrosion products on the surface should be cleaned, but do not remove any covering material.
The correct usage method of coating thickness gauge
1) The impact of attached substances. This instrument is sensitive to attached substances that hinder the probe from making close contact with the surface of the cover layer. Therefore, it is necessary to attach substances to ensure direct contact between the probe and the surface of the cover layer. When performing system calibration, the surface of the selected substrate must also be exposed and smooth.
(2) Interference from strong magnetic fields. We once conducted a simple experiment where measurements were severely disturbed when the instrument was operating near an electromagnetic field of around 10000 V. If it is very close to the electromagnetic field, there is still a possibility of crashing.
(3) Human factors. This situation often happens to new users. The reason why the coating thickness gauge can measure micrometers is because it can take small changes in magnetic flux and convert them into digital signals. If the user is not familiar with the instrument during the measurement process, the probe may deviate from the measured body, causing changes in magnetic flux and resulting in erroneous measurements. So it is recommended that users master the measurement method before using this instrument for the first time. The placement of the probe has a significant impact on the measurement, and the probe should be kept perpendicular to the surface of the sample during the measurement. And the placement time of the probe should not be too long to avoid interference with the magnetic field of the substrate itself.
(4) No suitable substrate was selected during system calibration. The small plane of the substrate is 7mm and the small thickness is 0.2mm. Measurements below this critical condition are unreliable.
