| 摘要 |
A particle detector, especially for smoke, comprises an emitter (20) which directs a cone of radiation towards a passage (16) through which air flows. A sensor (22) detects radiation reflected from the opposite walls (25a, 25b) and from any particles. An electrical control circuit generates an output signal which in the absence of particles is a compensated signal, e.g. for temperature changes, but which when particles are present is proportional to the number of particles. Changes in the output signal level are measured to give an analogue output. |
