| 摘要 |
PURPOSE:To achieve a quantitative measurement of electric characteristic of a conductor of double-layer structure at a high accuracy with a high reliability by providing two LC self-excitation oscillators different in the oscillation frequency to add or subtract rectified values of oscillation outputs thereof. CONSTITUTION:The oscillation frequency f1 of a first LC self-excitation oscillator comprising a transistor 30, a split air core coils 31A and 31B and capacitors 32 and 33 differs by more than 1.5 times from the oscillation frequency f2 of a second LC self-excitation oscillator comprising a transistor 40, split air core coils 41A and 41B and capacitors 42 and 43. Given f1=60MHz and f2=1.5MHz, outputs of both the oscillators are taken out via a rectification circuit 50 and subtracted being weighted so that a measuring signal turns to a signal only correlated with the thickness of a copper plated layer of a steel wire 10. As the value of the ratio of f1/f2 is by far larger than 1.5, there is no influence due to mutual interference therebetween. Thus, quantitative measurement of electric characteristic can be done at a high accuracy with a high reliability. |
