| 摘要 |
PURPOSE:To permit measurement of a longer distance and to improve the accuracy in the measurement by digitizing directly the voltages induced in a pair of secondary coils and taking the same into a computer. CONSTITUTION:When a magnetic field is generated by a primary coil 5, eddy current flows in a metallic body 1 to be measured and induced voltages are generated in a pair of secondary coils 6, 7. A pair of the induced voltages and the voltage impressed on a standard resistor 9 are time-dividedly measured by a voltage measuring device 12 through a scanner 11. A pair of the induced voltages are digitized by a voltage measuring device 12 and are fed to a computer 13, where the differential voltage thereof is calculated. At the same instant, the frequency of the excitation current in the coil 5 is monitored and digitized by a frequency counter 10 and is fed to the computer 13. The excitation current of the coil 5 is determined from the voltage impressed on the resistor 9 and the deviation from the set value is numerically corrected in the computer 13. The deviation of the excitation frequency from the set value is also corrected. The distance between a sensor on which the coils 5 and 6, 7 are wound and a metallic body 1 to be measured is determined in accordance with the differential voltage calculated in the computer 13.
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