Film thickness meter

The working principles of film thickness meters are mainly as follows:
Magnetic induction principle: suitable for measuring the thickness of non-magnetic coatings on ferromagnetic metal substrates. The instrument determines the coating thickness by measuring the change in magnetic flux between the probe and the substrate.
Eddy current principle: used to measure the thickness of non-conductive coatings on non-ferromagnetic metal substrates. The high-frequency electromagnetic field generated by the probe generates eddy currents in the substrate. Changes in coating thickness affect the size of the eddy currents, thereby measuring the coating thickness.
Ultrasonic principle: The coating thickness is measured by using the difference in the propagation speed of ultrasonic waves in different media. The probe emits ultrasonic waves, which are received after reflection from the coating and substrate, and the coating thickness is calculated by measuring the propagation time of the ultrasonic waves.