Magnetic induction measuring principle thickness gauge
When using the principle of magnetic induction, the thickness of the coating is measured by using the magnitude of the magnetic flux flowing from the probe through the non-ferromagnetic coating and into the ferromagnetic substrate. The corresponding magnetic resistance can also be measured to indicate the coating thickness. The thicker the coating, the greater the magnetic resistance and the smaller the magnetic flux. Thickness gauges that use the principle of magnetic induction can in principle have the thickness of non-magnetic conductive coatings on magnetically permeable substrates. Generally, the magnetic permeability of the base material is required to be above 500. If the coating material is also magnetic, the difference in magnetic permeability from the base material is required to be large enough (such as nickel plating on steel). When the probe with the coil around the soft core is placed on the sample being tested, the instrument automatically outputs the test current or test signal. Early products used a pointer-type meter to measure the magnitude of the induced electromotive force. The instrument amplified the signal and then indicated the coating thickness. In recent years, circuit design has introduced new technologies such as frequency stabilization, phase locking, and temperature compensation, and magnetoresistance is used to modulate measurement signals. It also uses state-of-the-art integrated circuits and introduces microcomputers, which greatly improves the measurement accuracy and reproducibility (almost by an order of magnitude). Modern magnetic induction thickness gauges have a resolution of 0.1um, an allowable error of 1%, and a measuring range of 10mm.
The magnetic principle thickness gauge can be used to accurately measure the paint layer on the steel surface, porcelain and enamel protective layers, plastic and rubber coatings, various non-ferrous metal plating layers including nickel and chromium, and various anti-corrosion coatings in the chemical and petroleum industries. coating.
