| 摘要 |
A fire detector of the ionization type is characterized by sensitivity compensating circuitry. The detector includes an ionization chamber in series circuit with a reference impedance to form a voltage divider, and circuitry for sensing the voltage at the juncture between the ionization chamber and reference impedance and for generating a current flow which changes in value with changes in the voltage. The sensitivity compensating circuitry monitors the current flow, and for slowly occurring changes corresponding to slow changes in the juncture voltage adjusts the current flow to and maintains the flow at a quiescent value. The compensating circuitry responds relatively slowly to changes in current flow, and therefore does not significantly affect the current flow in response to a rapid change in juncture voltage. Thus, upon the occurrence of products of combustion within the ionization chamber, a relatively rapid change occurs in the juncture voltage to cause at least a predetermined change in the current flow, in response to which an alarm is generated.
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