| 摘要 |
PURPOSE:To take a corresponding countermeasure speedily by detecting the open phase of a pair of signals in an incremental two-phase encoder when the signals are in the open-phase state and deciding abnormality. CONSTITUTION:The 90 deg. out-of-phase A-phase and B-phase outputs 2 and 3 of the incremental two-phase encoder 1 are supplied to a processing circuit 4, which generates pulses by a part 5 at the leading-edge and trailing-edge parts of the A-phase and B-phase pulses 2 and 3, multiply the pulses by two, and send the signals to an open-phase detecting circuit 20. When the pulse 2 enters the open-phase state and is held at a high potential, a clear pulse input for the counter of the A-phase monitor circuit 21 misses, B-phase doubled pulses are counted successively, and an output appears at a terminal 26, so that the output 34 of the circuit 20 becomes an 'H' signal indicating the open- phase state. Further, when the B-phase is open, the output 34 rises to 'H' by the similar function of a B-phase monitor circuit 27.
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