| 摘要 |
PURPOSE:To detect a speed in a wide speed range from a low speed to a high speed with good accuracy, by using a speed detector for outputting two sine wave signals which have phases different by 90 deg. to each other and of which the frequencies are proportional to the speed of a rotor or moving body. CONSTITUTION:A motor 5 has an encoder 6 mounted to the motor shaft thereof and two sine wave signals, which have phases different by 90 deg. to each other and of which the frequencies are proportional to speed of rotation, are outputted from said encoder 6. As the number of rotations of the motor 5 becomes larger, the pulse interval of rectangular wave pulses becomes small and the frequency dividing ratio of a frequency divider 18 changes and a counter 25 is constituted so as to count a clock pulse fC applied at a pulse interval T1 at first but to be capable of subsequently counting the clock pulse fC applied at a two-pulse interval T2 to prevent the lowering in measuring accuracy due to the lowering in a count time.
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