光学烟雾探测器灵敏度研究

Analysis of the Optical Smoke Detector Sensitivity

传导型光学烟雾探测器的可靠性会受到光学元件寄生效应灵敏度的影响,特别是温度。剧烈温度变化的影响,不能通过滤波器消除。因为它的光谱和烟火吸收系数的光谱有重叠。本文得出了传导型光学烟雾探测器对温度的传递函数。利用光电子二极管系统的二阶热学模型,得出了光源和接收器二极管结点温度差的稳态解析式。基于对热系统的分析,得出了和RC低通滤波器模型等效的框图。在此框图的基础上,对如何消除环境温度变化和探测器响应的阈值灵敏度的影响进行了分析。

Reliability of the transmission-type optical smoke detectors is affected by sensitivity of optical components to parasitic effects, especially to temperature. Influences of high rate temperature variations cannot be eliminated by filtering, as their spectral range partially overlaps with the spectral range of a fire absorption index. The transfer functions of the transmission-type optical smoke detector are derived in this paper. Using the second-order thermal model for the thermal system of the optoelectronic diodes, an expression is given for the steady-state solution of the difference of the source and the receiver diode junction temperatures. On the basis of the thermal system analysis, a block of diagram is equivalent to RC low-pass filters that model the pn junction temperature dependence on ambient temperature. On the basis of block diagram, the analysis is performed to establish how to eliminate the detector threshold sensitivity to ambient temperature variations.