PURPOSE: To prevent the unstability of control circuits by counting the output pulses of a pulse encoder in accordance with rotating directions, and emitting an alarm when the value thereof and the signal emitting one pulse at one revolution of the pulse encoder are not in a correct relation.
CONSTITUTION: The outputs of photodetectors 21, 22 of a pulse encoder are waveform shaped 31, 32, and are discriminated of directions; at the same time, they are converted 34 to quadruple frequency signals. The outputs thereof are supplied to an addition-subtraction counter 35. On the other hand, the output of a photodetector 25 emitting one pulse per revolution of a circuit slit is waveform shaped 33, and the output of the counter 35 is gated by this signal and is supplied to a register 36. When the pulse encoder is operating correctly, a value of 0 or 4N is set in the register 36. When the register 36 sets values other than these, an abnormality discriminating circuit 37 detects this and emits an alarm.
AMAMIYA YOUICHI
ASAHARA SUNAO
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