Isotope smoke detection instrument - has ionisation chamber monitored by IGFET suitably connected to supply terminals and to comparator

摘要

The detector has at leat on ionisation chamber whose voltage is monitored by an IGFET. The FET (1) drain (2) is connected through a resistor (6) and capacitor (7) to the terminals (13, 12) of a supply circuit and directly to a comparator (10). It is also periodically connected through resistor (4) and switch (5) to the supply terminal (12). The comparator (10) is connected directly to the supply terminal (12) and through an RC circuit (8, 9) to its terminal (13). Control terminal of a flip-flop (11) is connected between the comparator (10) and the RC circuit (8, 9).