Application of pulsed eddy current and ultrasonic sensors in paint film thickness measuring

Online paint film thickness measuring is important in the production of continuous coating line. A method of film thickness measuring using pulsed eddy current (PEC) and ultrasonic sensors without contacting the film itself is proposed. PEC is a new nondestructive testing (NDT) technique which using a broadband pulse excitation with rich frequency information and has wide application potentials. An ultrasonic sensor and a PEC sensor were placed in adjacent position. Where the ultrasonic sensor measures the distance between the device and the upper surface of the paint film and the PEC sensor measures the distance between the device and the upper surface of the substrate. Compared the two distances the film thickness value was produced. The device is capable of accurately measuring thickness of various paint films, such as flat, glossy and metal-flake containing paint films. The method may be applied to continuous coating line. Laboratory experiments proposed the accurate and efficient.