| 摘要 |
A sensor apparatus (22) and a safety apparatus (24) which can ensure significantly enhanced safety by monitoring constantly whether the sensor apparatus (22) is operating normally. An auxiliary electrode plate (80) of a small area is disposed in parallel and in opposition to an electrode plate (26) with a short distance therefrom. A switching element (90) is turned on every second for a period of milliseconds repetitively. When the switching element (90) is turned on under the control of a central processing unit (74), the auxiliary electrode plate (80) is connected to the ground potential, as a result of which a capacitance (”C) effective between the auxiliary electrode plate (80) and the electrode plate (26) is electrically connected in parallel with a capacitor (C 0 ) effective between the electrode plate (26) and a machine component (18), resulting in that the capacitance (C 0 ) is increased by a proportion corresponding to the capacitance (”C). Consequently, change of the capacitance (C 0 ) comparable to that brought about upon detection of the human body takes place, whereby a substantially similar detection signal as the human body detection signal is made available. On the basis of this detection signal, it is possible to monitor whether or not the sensor apparatus (22) is operating normally. |
