| 摘要 |
<p>PURPOSE:To provide a rotating speed detector in which a detectable distance can be increased by using one detecting element and influence of waviness due to an eccentricity is suppressed and which can obtain a stable detection output. CONSTITUTION:A change of a magnetic field due to a rotation of a rotor is detected by a detecting coil provided in a resonance circuit 2 of a detector 1. The circuit 2 receives a resonance current from an oscillator 3 and generates a high-frequency magnetic field. A reference voltage Vr is obtained by a reference voltage circuit 5 according to an oscillation output of the oscillator 3. An output voltage Vs of the detector 1 and the voltage Vr are rectified by rectifiers 41, 42, and differentially amplified by a differential amplifier 6. An output voltage Vsub of the amplifier 6 is compared with a comparison voltage Vth by a comparator 7 to obtain a detection signal responsive to an uneven part of the rotor. Accordingly, even of an absolute value level of the output of the detector 1 is varied, unevenness of the voltage Vsub of the amplifier 6 to a distance between the rotor and the coil can be suppressed to a small value.</p> |
