| 摘要 |
PURPOSE:To improve the accuracy of pulse interval and to reduce the power consumption by providing a coil receiving an output of a high frequency oscillator and a capacitor whose capacitance whose capacitance is changed differentially by a mechanical displacement. CONSTITUTION:Plural metallic conductor strips 13 are provided radially toward an index disc 14 on a rotary disc 12 at an angular pitch P, and the conductor strips 13 are connected in common and grounded. A pair of outer and inner metallic conductor strips 15A, 15B are provided similarly to the index disc 14 as above and the conductor strips 15A, 15B are arranged with a phase difference in the turning direction of the disc 11. The conductor strips 15A, 15B are connected electrically and a variable capacitor is formed between the conductor strips 13 and the conductor strips 15A, 15B. The said variable capacitor and the coil 17 form a tank circuit, to which a high frequency oscillation output is applied. Thus, a pulse output number in response to number of mechanical changes is obtained at an output terminal 25 by using a diode 22 and a capacitor 23 so as to detect an output obtained at the coil 21 by the mechanical displacement by the rotation of the disc 11. In this case, the accuracy of pulse interval is used as a mean value of the pulse number over the entire rotating body and highly accurate value is obtained.
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