| 摘要 |
A heat detector having automatic gain control in relation to changes of time constant different from that of the changes to be detected, comprises an outer feedback loop including the light path between emitter (10) and detector (14), and an inner feedback loop (40,42,44) around the emitter drive circuit. The inner feedback loop contains an exponential element (42). The exponential response of the inner loop feedback circuit makes the open-loop gain and the time constant of the system invariable in spite of differences in the light path, for example in different installations.
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