发明名称 |
Detecting the presence of a fire |
摘要 |
Apparatus for detecting the presence of a fire includes a pair of detectors for radiation characteristic of a fire, e.g. at 4.3 microns, and a further detector for radiation characteristic of a black body, e.g. at 3.8 microns. Filters select the detector output components at flame flicker frequencies. The filtered outputs of the detector pair are cross-correlated to produce a relatively noise-free signal. This signal is divided by a factor obtained by cross-correlating the further detector filtered output with the average of the detector pair filtered outputs. The result of the division is applied to a threshold-responsive circuit. Thus the relatively noise-free signal is effectively subjected to a threshold which is proportional to the degree of similarity between the variations with time of the output signal of the further detector and the output signals of the detector pair.
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申请公布号 |
US5612537(A) |
申请公布日期 |
1997.03.18 |
申请号 |
US19940298307 |
申请日期 |
1994.09.01 |
申请人 |
THORN SECURITY LIMITED |
发明人 |
MAYNARD, STEVEN P.;BASHAM, PAUL J.;PLEYDELL, MARK E. |
分类号 |
G08B17/12;(IPC1-7):G08B17/12 |
主分类号 |
G08B17/12 |
代理机构 |
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代理人 |
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主权项 |
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地址 |
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