| 摘要 |
PROBLEM TO BE SOLVED: To detect voltage abnormality of a back-up power source by monitoring the voltage of the back-up power source when power supply from a main power source is cut off. SOLUTION: An absolute encoder 20 includes the back-up power source 26, and detects and holds position information of an object to be detected 18 by electric power supplied from the back-up power source 26 when the power supply from the main power source 14 is cut off. The absolute encoder 20 further includes a regulator circuit 38 for regulating output voltage from the back-up power source 26 to a predetermined voltage, and a voltage abnormality information holding device operated at the predetermined voltage. The voltage abnormality information holding device is composed of a voltage abnormality detection circuit 36 for detecting the output voltage of the back-up power source 26 out of a predetermined range by monitoring output voltage of the back-up power source 26 while the main power source 14 is turned off, and a voltage abnormality information holding part 54 for storing detected voltage abnormality information. COPYRIGHT: (C)2008,JPO&INPIT
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