| 摘要 |
PROBLEM TO BE SOLVED: To obtain an alarm detection circuit with high stability against fluctuation in ambient temperature and fluctuation in power supply voltage. SOLUTION: When an electric signal (a) from an input terminal 2 is interrupted, a voltage signal (b) that is an output of an amplifier 7 is interrupted and no voltage is applied to a capacitor 10. A peak voltage charged in the capacitor 10 is discharged by a time constant consisting of a capacitance of the capacitor 10 and a resistance of a resistor 13, then a stored voltage signal (d) is being decreased exponentially. When the voltage signal (d) reaches a preset threshold value (e) at an input terminal 14 or below, a comparator 15 outputs an alarm signal (f), which is informed externally via an output terminal 16. Since the same models are used for diodes 8, 9, the characteristic change due to fluctuation in ambient temperature and fluctuation in power supply voltage is the same for the diodes and no error is caused for an alarm detection time by the comparator 15. |
