Cyflwyniad o Esty Cyfredol Mesuriad Egwyddor o Cotio Trwch Gauge
The high-frequency AC signal generates an electromagnetic field in the probe coil, and when the probe is close to the conductor, eddy currents are formed in it. The closer the probe is to the conductive substrate, the greater the eddy current and the greater the reflection impedance. This feedback action characterizes the size of the distance between the probe and the conductive substrate, that is, the thickness of the non-conductive coating on the conductive substrate. Because this type of coating thickness gauge probe is designed to measure the thickness of coatings on non-ferromagnetic metal substrates, it is often called a non-magnetic probe. Non-magnetic probes use high-frequency materials as coil cores. Compared with the principle of magnetic induction, the main difference is that the probe of the coating thickness gauge is different, the signal frequency is different, and the signal size and scale relationship are different. The coating thickness gauge using the principle of eddy current can measure non-conductive coatings on all conductive substrates in principle, such as paint and plastic coatings on the surface of aerospace vehicles, vehicles, household appliances, aluminum alloy doors and windows, and other aluminum products. and anodized film. The coating material has a certain conductivity, which can also be measured through calibration, but the ratio of the two conductivity is required to be at least 3-5 times different. Although steel substrates are also conductors, the magnetic principle of measuring coating thickness is more suitable for this type of task.
