METHOD AND DEVICE FOR ELECTROMAGNETIC INDUCTION TYPE THICKNESS MEASUREMENT

摘要

PURPOSE:To improve the measurement accuracy of a thickness sensor in outdoor operation by adding a force adding function to a sensor part. CONSTITUTION:A sine wave of frequency in a high frequency range from a variable frequency AC power source 4 is used to balance a bridge circuit 2 and then while a test coil 1 is pressed against a body to be measured by a pressure application driving part 5 with constant force, the sine wave in the high frequency range is impressed to the test coil 1 to measure the corrosion of the body to be measured or the thickness of its coating layer by using the measured voltage of the bridge circuit 2 and the corrected value which is generated previously and excludes the influence of corrosion thickness, etc., of various materials. Then, a sine wave of low frequency is impressed to the test coil 1 by a similar procedure to find the overall thickness of the body to be measured from the output voltage of the circuit 2 and the corrected value which is generated previously and excludes the influence of corrosion thickness of various materials, and then the real thickness of the body to be measured is measured from the difference between the corrosion thickness and the overall thickness of the body to be measured including the corrosion layer.