Fire alarm responding to flame radiation and individual sparks - is esp. for pipelines and chimneys and compensates for day-night radiation variations

摘要

The alarm has an opto-electrical transducer (16) which supplies a measuring signal to an amplifier (VI). This has a resistive feedback loop and its output is coupled via a series capacitor (32) and resistor (34) to an evaluation circuit using a threshold amplifier for providing the alarm signal. The amplifier (VI) can also respond to signals from the transducer (16) representing individual sparks and it pref. comprises an operational amplifier (18) with two series feedback resistors (26, 28) their junction coupled to the negative voltage rails (-V) via a capacitor (30). The transducer (16) comprises a photo-element coupled in series with a capacitor (22) and a resistor (24) across the amplifier inputs. THe feedback signal is applied to the inverting input of the operational amplifier (18) and its non-inverting input is coupled to the negative supply rail (-V) via a resistor (20).