Rate-of-change combustion and contamination detection device

Details Rate-of-change combustion and contamination detection device Rate-of-change combustion and contamination detection device

1973-12-13

1976-03-23

Caldwell, John W.

Communications: electrical

Systems

Call station

250381, G08B 1710, H01J 3928

Patent

active

039463745

ABSTRACT:
An ionization-type gas contamination detector, intended primarily for use as a fire detector, in which a substance which emits predominantly low-energy beta particles is used as an ionizing radiation source in an ionizing chamber. Rapid changes in ionization current, which indicate the present of a fire or smoke preceding a fire, are detected and an alarm is energized by a rate-of-change circuit in response to such changes. The output of the ionization chamber is amplified, and a level detector energizes the alarm when the amplified chamber output reaches a predetermined level. The output of the amplifier is adjusted relatively slowly to a reference level. In one embodiment, the amplifier output is adjusted to the reference level by the activation of a sample-and-hold feedback loop for a short period of time. In another embodiment, continuous feedback through a circuit with a relatively long time constant provides the desired adjustment. This feature makes the device relatively insensitive to normal atmospheric and environmental changes, while being very sensitive to changes in the level of combustion products in the atmosphere.

REFERENCES:
patent: 3233100 (1966-02-01), Lampary
patent: 3516083 (1970-06-01), Meyer
patent: 3548205 (1970-12-01), Ogden
patent: 3559196 (1971-01-01), Scheidweiler
patent: 3778796 (1973-12-01), Honda

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