| 摘要 |
PROBLEM TO BE SOLVED: To reduce time required for detecting intermittent failure by counting the number of times of occurrence of faulty condition to detect failure in an input/output circuit, detecting transient faulty condition in relays or external input, excluding the latter faulty condition from the above-mentioned count to count only the occurrence of faulty condition due to failure, and, when the count reaches a specified number, outputting a failure signal. SOLUTION: If the same condition as faulty condition is transitionally caused by delay in operation due to variation in the state of relays or external input, not due to the occurrence of failure, only an output signal OS is produced in the beginning. Then a faulty condition signal FS is produced to cause a counter to count. When both the signals overlap each other, a normal condition signal NS is output. At the end of the signal, only an answer signal AS is produced, and a faulty condition signal FS is output. In this case, the count increased by '1' by the first normal condition signal is decreased by the second normal condition signal NS, and is not added to the number of times of failure detection. This makes it possible to swiftly detect failure the duration of which is unstable, that is, long at some time and short at other times. |
