Threshold determination apparatus and method
First Claim
1. An apparatus for determining an alarm threshold of a detector having an internal, variable, characteristic parameter which corresponds to an external detector value, the detector also having a test condition, the apparatus comprising:
- means for sensing a value from the detector corresponding to a first condition at the detector and a first internal parameter value and for sensing a value from the detector corresponding to the detector test condition;
means for determining a selected, incremental change of the internal parameter value from the parameter value corresponding to the first condition;
means for converting said internal parameter incremental change to a detector specific incremental value; and
means for combining said detector specific incremental value with said value corresponding to said first condition thereby forming the alarm threshold.
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Accused Products
Abstract
A system and method for establishing an alarm threshold for each member of a plurality of detectors or sensors includes storing a value returned from each detector indicative of a clear air condition. A second value returned from each detector indicative of a test condition is stored. The stored values are combined with a common detector characteristic value to produce a unique alarm theshold for each detector. The determined alarm thresholds can be stored for subsequent use. Subsequently, a value returned from a detector indicating a current ambient condition can be compared to that detector'"'"'s previously determined alarm threshold. If the currently returned value from the detector exceeds the predetermined alarm threshold, an alarm condition can be indicated.
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Citations
27 Claims
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1. An apparatus for determining an alarm threshold of a detector having an internal, variable, characteristic parameter which corresponds to an external detector value, the detector also having a test condition, the apparatus comprising:
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means for sensing a value from the detector corresponding to a first condition at the detector and a first internal parameter value and for sensing a value from the detector corresponding to the detector test condition; means for determining a selected, incremental change of the internal parameter value from the parameter value corresponding to the first condition; means for converting said internal parameter incremental change to a detector specific incremental value; and means for combining said detector specific incremental value with said value corresponding to said first condition thereby forming the alarm threshold. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. An apparatus usable in a distributed detector system for establishing an alarm threshold for at least some of the detectors while the respective detectors are in clear air comprising:
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a control unit; means, coupled between the detectors and said control unit, for communicating bidirectionally; means for causing a selected detector to return a clear air output value, via said communicating means, to said control unit; means, carried by said control unit, for placing the selected detector into a test condition and for causing the detector to return a test output value, via said communicating means to said control unit; means, carried by said control unit for storing said clear air output value and said test output value; and means for combining at least said clear air output value with a predetermined incremental value to form a detector specific alarm threshold. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17)
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18. A method of establishing an alarm threshold for each member of a group of detector units coupled to a common communication line comprising the steps of:
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(a) storing a value, common to each of the detectors, indicative of an expected incremental variation in a detector parameter between a clear air condition and an alarm condition; (b) selecting a detector; (c) sensing and storing a value returned from the selected detector indicative of a clear air condition at the detector; (d) sensing and storing a value returned from the selected detector indicative of a test condition at the detector; (e) combining at least the value indicative of clear air and the common incremental value to produce an alarm threshold for the selected detector; (f) storing the alarm threshold; and selecting another detector and repeating steps (c) through (f). - View Dependent Claims (19, 20, 21)
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22. A multiple detector fire alarm system comprising:
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a plurality of detectors with each member of said plurality having an input/output communication port, circuitry for detecting an ambient condition and circuitry for generating a value at the port indicative of the ambient condition; a control unit displaced from said detectors; means for coupling said control unit to a said respective port of each member of said plurality; said control unit including means for storing an incremental parameter common to the members of said plurality; means for sensing a value from each said detector corresponding to a respective ambient condition; and means for establishing an alarm threshold for each said detector responsive to a respective one of said detector ambient condition values and said stored common incremental parameter. - View Dependent Claims (23, 24, 25, 26, 27)
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Specification