| 摘要 |
PURPOSE:To enable highly accurate detection of speed and position, by inversely adding to a control voltage of a VCO a voltage as the results of sampling and holding the control voltage. CONSTITUTION:A scale 1 is read out with scale detectors 2a, 2b and 2c to output three phases of carrier waves shifted by 120 deg. from one another. These carrier waves are modulated with multipliers 5a, 5b and 5c and added up with an adder 6. Then, the output frequency of the adder 6 is multiplied N times with a PLL circuit 7 and a reference phase comparison signal 9 with the frequency of N.fc is compared in the phase with a control voltage of an output VCO of the circuit 7 by a position demodulating circuit 8 to determine the potential difference between the both. Then, right and left hand moving pulses 13 and 14 obtained from the circuit 8 are integrated with a reversible counter 10. Then, the VCO control voltage, a moving direction signal 12 from a direction discrimination circuit 8h and pulses 13 and 14 enter a speed voltage conversion circuit 11 to remove the drift and offset of the VCO and a voltage, namely, a speed voltage 16 are outputted corresponding to the speed.
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