EDDY-CURRENT TYPE SAMPLE MEASURING METHOD, EDDY-CURRENT SENSOR AND EDDY-CURRENT TYPE SAMPLE MEASUREMENT SYSTEM

摘要

PROBLEM TO BE SOLVED: To solve such a problem that an alternating voltage applied to an exciting coil wound around a ferrite core cannot be kept constant, thus causing a measurement error because of the influence of inductance and resistance components of a lead wire connected between the exciting coil and an alternating voltage power source.;SOLUTION: A voltage detection coil is provided differently from the exciting coil which generates an alternating magnetic field in the magnetic core of an eddy current sensor, and the induction voltage of a voltage detection coil at generation of eddy current is detected by a detector with a high input impedance in relation to the impedance of the detection coil. The high-frequency voltage applied to the exciting coil is controlled by the detection voltage detected by the detector. Using an eddy current sensor for measurement and an eddy current sensor not for measurement which does not measure a sample, the voltage detection coils provided differently from the exciting coil to the magnetic cores of the respective eddy current sensors are connected in parallel with each other so that the respective induction voltages are in the opposite directions, and the voltage difference between the induction voltage of the detection coil of the eddy current sensor not for measurement and the induction voltage of the detection coil of the eddy current sensor for measurement which has measured the sample, is detected by measurement terminals of the voltage detection coils connected in parallel with each other.;COPYRIGHT: (C)2009,JPO&INPIT