公开(公告)号：US3820097A

公开(公告)日：1974-06-25

申请号：US35174073

申请日：1973-04-16

Applicant: HONEYWELL INC

Inventor： LARSON M

IPC: F23N5/08 ,  G08B17/12

CPC classification number: F23N5/082 ,  F23N2023/20 ,  F23N2029/08 ,  F23N2029/16 ,  Y10T307/773

Abstract: A flame detection system utilizes a flame responsive impedance, such as a lead sulphide photocell, and responds to the change in infrared radiation and the flame flicker frequency of the sensed flame. The flame responsive impedance is connected through a variable impedance means to a source of direct current voltage. The voltage between the flame responsive impedance and the variable impedance means is compared by an amplifier to a voltage divider network so that a feedback voltage can be generated by the amplifier to control the variable impedance means. The variable impedance means is controlled by the feedback so as to keep the direct current voltage across the flame responsive impedance constant to compensate for variations in flame background radiation, and cell to cell variation. The system then uses a band-pass amplifier and detector-integrator system to control an output switch.