| 摘要 |
<p>PROBLEM TO BE SOLVED: To control the sensitivity of entire hot-wire sensor according to environmnetal temperature. SOLUTION: Four pyroelectric elements having different polarities are connected in series. A control device 16 determines according to the output voltage of a temperature detection element 7, a threshold to be given to a comparator 15 and the number of pulse counts for judging whether or not a detection signal is outputted after a pulse count circuit 14 counts the number of pulse signals from the comparator 15. When the pulse signal is outputted from the comparator 15, the control device 16 counts the number of pulse signals, and when the counted value is at least a predetermined number of pulse counts, the control device 16 judges that the object has been detected and outputs a detection signal thereafter.</p> |
