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MEASUREMENT FOUNDATION
ZCT AUTO
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10. Notice for instrument use
The main factors which have impact on the measuring accuracy of the instrument: the metal magnetic prop-
erty of basal body, the thickness of basal body, edge effect, curvature, surface roughness degree, external
magnetic ield, attached materials, the pressure of measuring head, the position of measuring head, deforma
-
tion of test piece and so on.
1. THE FACTORS WHICH AFFECT MEASURING ACCURACY AND RELEVANT INSTRUCTIONS
1) The metal magnetic property of basal body
The thickness measurement by magnetic property method is affected by the change of metal magnetic property of basal
body. (In practical applications, the change of magnetic property of low-carbon steel can be considered as minor). In order
to avoid the effect of heat treatment and cold working factors, standard piece with the same property as the basal body metal
of test piece should be used to calibrate instrument. The test piece which is about to be coated can also be used to calibrate
instrument.
2) The thickness of basal body mental
Each instrument has a critical thickness of basal body metal. If the thickness of basal body metal is greater than the critical
thickness, measurement will not be affected by the thickness of basal body metal. The critical thickness value of this instru-
ment is 0.5mm.
3) Edge effect
The instrument is sensitive to the sudden change of surface shape of test piece. Therefore, it is not reliable to measure near
the edge of test piece or the internal corner.