| 摘要 |
A presence sensing system provided with self-checking operation is disclosed. The system is especially adapted for use in a control system for machines to ensure safe operation thereof. The system comprises a presence sensing section capable of producing output signals indicative of normal, intrusion, and withdrawal conditions in the guarded zone of the machine. A control system comprising a control channel and a self-checking channel responds to the output signals of the sensing section and control the condition of a controller, which in turn is adapted to interrupt machine operation. The control channel and the self-checking channel are both implemented in binary logic. The system is operated under the control of timing means which causes cyclic operation with each cycle divided into separate time slots, one for a testing mode of operation and one for a condition sensing mode of operation. The testing mode time slot is subdivided into plural time slots, each corresponding to a particular test of the system. |
