Importance

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Abstract

The present invention relates to a judgement circuit for determining rotation or non-rotation of a motor, and to a motor stopped verification apparatus using such judgement circuit. A signal from a rotation sensor which detects rotation of the motor is input to the judgement circuit and a threshold value judgement made using a fail-safe two input window comparator. That is, respective predetermined threshold value ranges (windows) are set for each terminal of the window comparator, so that when the motor is stopped and the judgement circuit and the sensor are normal, the level of the signal input to each terminal comes within the range of the window, and an output of logic value 1 is generated from the window comparator. When the sensor or the judgement circuit is faulty then the signal level of one of the input terminals becomes outside the window range, while when the motor is rotating, the signal level of the other input terminal becomes outside the window range so that in either case an output of logic value 0 is generated. The stopped condition of the motor can thus be distinguished from rotation under inertia, thus enabling reliable detection.

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First Claim