GB/T 7991.5-2014Test method of viterous and porcelain enamels—Part 5: Determination of thickness by electromagnetic mothod (English PDF)

3.1 Magnetic base metal

Affected magnetic gauge base metal magnetic change (change in magnetic low carbon steel may be considered minor), in order to avoid heat treatment

Standards and cold factors, application and DUT base metal of the same nature to calibrate the instrument. Preferably by firing simulation

Metal matrix heat treatment process before the glass-lined not calibrated.

3.2 the base metal thickness

Each instrument is DUT base metals requires a critical thickness beyond this thickness, the measured value will not be base metal

The impact of increased thickness. If the instrument manufacturer is not critical thickness values of this station apparatus is provided, it shall be determined by experiment.

3.3 Edge Effect

DUT mutations will affect the accuracy of the surface shape of the magnetic thickness gauge. So, too close to the number of test DUT at the edges or corners

It is not reliable unless the above conditions for the instrument calibration done. This effect may extend to the corners at 15mm.

3.4 Curvature

The smaller the radius of curvature of the DUT, the more significant the impact. This has a significant relationship with the type of instrument.

With the thickness measurement of a bipolar probe, the probe placed parallel to the cylinder axis or vertical, readings will be different. If unipolar probe

Probe irregular wear occurred, it would have a similar phenomenon.

Therefore, before the bend specimens measuring instrument to be calibrated specifically for this case. Otherwise, the measurement data is not reliable.

3.5 Surface roughness

If the DUT within a rough surface area measured by reference to the same range of values significantly exceeds the inherent repeatability of the instrument, the

At some point the number of measurements should be increased to at least 5 times.

3.6 matrix metal machining direction

When the probe with bipolar or unipolar uneven wear probe measuring instrument, instrument readings will be magnetic matrix metal machining (eg […]