| 摘要 |
PURPOSE:To enable detection of abnormality in a rotation detector, even in case of zero rotation, by providing means for judging whether a pulse signal has a level between predetermined upper and lower levels and means for detecting abnormality in the rotation detector based on an output signal from the judging means. CONSTITUTION:A level judging unit 14 judges whether the voltage level of a pulse signal is between predetermined upper limit (Va) and lower limit (Vb). For example, the upper limit Va is set to a lowest threshold voltage at which an inverter 6 outputs a Low signal and the lower limit is set to a highest threshold voltage at which the inverter outputs a High signal. In other words, the voltage between Va and Vb is an abnormal voltage at which it is not clear whether the inverter 6 outputs a Low signal or a High signal. |
