| 摘要 |
PURPOSE:To enable the measurement of film thickness by inserting a probe having a coil into a coated pipe, generating eddy current in the body and coating film of the coated pipe of conductor and detecting the eddy current of the conductor due to change in the thickness of the coating film. CONSTITUTION:When AC is flowed to a coil 2 from a high frequency power source 1 and the coil is brought near a conductor M, eddy current 4 is generated in the conductor M. Since the current 4 changes with the distance from the coil and the thickness and the material quality of the conductor M, the thickness of the conductor and the thickness of the coating film can be measured by detecting the change in the eddy current. Two methods depending upon the state of an object are as follows; 1, in the case of measuring the non-conductor film on the conductor, the probe is brought into contact with the object, and the distance between the coil and the conductor changes with a change in the thickness of the non-conductor film, then the eddy current changes as well, and the thickness of the non-conductor film can be detected from said change. 2, in the case of measuring the conductor film on the conductor, and if there is a difference between the conductivities of both conductors, the eddy current flows more through the film as the thickness of the film increases and conversely when the thickness of the film is thin, the eddy current flows more in the base metal; therefor, the measurement of the film thickness is made possible by comparing the same with standard data. |
