| 摘要 |
PROBLEM TO BE SOLVED: To improve safety by always supervising whether a sensor is normally operated or not. SOLUTION: This device arranges an auxiliary electrode 80 of small area opposed in parallel relating to an electrode plate 26 adjacently to it. A switching element in a switching circuit 88 is turned on by a millisecond order at each second, so as to always repeat this action. When the switching element is on- driven by a central processing unit 74, the auxiliary electrode 80 is grounded, a capacity ΔC between the auxiliary electrode 80 and the electrode plate 26 by this grounding is connected in parallel to a capacity C0 between the electrode plate 26 and a roller 18. A ΔC component is increased relating to the capacity C0. In this way, a change amount of an electrostatic capacity similar to detection of the human body is obtained by increasing of this electrostatic capacity, and a detection signal similar to detection of the human body is output. A sensor device 22 can be supervised for whether it is normally operated or not. |
