| 摘要 |
PURPOSE:To monitor a signal exactly, by detecting a continuation time of the signal by use of a counting circuit, and also prescribing the time width of instantaneous disconnection strictly, in a signal monitoring device to be used for a discharge alarm system, etc. CONSTITUTION:When a response signal is received by a receiving part REC, an on-rise detecting part DET1 detects on-rise, sends a clock signal to a counter (cd) through a holding part HLD and an AND circuit AND1, and the clock signal is counted by the counter (cd). Also, an off-detecting part DET2 counts the clock signal while a digital signal is off. In this case, when a count value of the counter (cd) reaches a signal continuation deciding coefficient shown by a resistor R1, a signal continuation detecting signal is outputted from a comparator COM1. Also, when a count value of a counter (cb) reaches an instantaneous disconnection deciding coefficient shown by a resistor R2, the counter (cd) is reset through the holding part HLD by an output of a comparator COM2. |
