US 6,583,404 B1Granted

Photoelectric smoke detecting apparatus

AssigneeNohmi Bosai Ltd.

InventorShigeru Sakurai

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Abstract

A photoelectric smoke detecting apparatus capable of generating analog data accurately indicating a smoke density regardless of a presence or absence of contamination. A control unit for outputting the analog data corresponding to the smoke density based on a detection value derived from the output of a smoke sensor includes a smoke density arithmetic module having a characteristic function for converting the detection value to a smoke density value, a zero-density detection value storage device for storing a detection value at a time point when the smoke density is zero as a zero-density detection value, a change ratio arithmetic module designed for arithmetically determining a ratio of change representing a change of the zero-density detection value, and a compensation arithmetic module designed for compensating conversion characteristic for converting the detection value to the smoke density value based on the ratio of change. The compensation arithmetic module is designed to cause the smoke density arithmetic module to generate the smoke density value in such a manner to counter a change of an output characteristic of the detection value for of the smoke density, which change depends on the ratio of change. A self- or auto-compensation function against aged deterioration of the detection value due to contamination is realized.

Claims21

Dependent claims

A photoelectric smoke detection apparatus comprising:

a smoke sensor comprising a labyrinth inner wall, a chamber enclosed by said labyrinth inner wall, a light emitting element disposed within said labyrinth inner wall and operable to emit light and a light receiving element disposed within said labyrinth inner wall so as to receive at least a portion of the light and operable to output a detection signal indicative of a detection value corresponding to a smoke density prevailing within said chamber enclosed by said labyrinth inner wall;
and
a controller operable to output a smoke density value, as analog data, corresponding to the smoke density prevailing within said chamber, said controller comprising a smoke density arithmetic module operable to convert the detection value to a first smoke density value via a characteristic function located therein, a zero-density detection value storage unit operable to store a zero-density detection value that corresponds to zero smoke density prevailing within said chamber, a change ratio arithmetic module operable to arithmetically determine a ratio of change representing a change of the zero-density detection value and a compensation arithmetic module operable to provide a compensating value based on the ratio of change to said smoke density arithmetic module,
wherein said smoke density arithmetic module is further operable to change the characteristic function, based on the compensating value, such that said smoke density arithmetic module is operable to convert the detection value into the smoke density value.

1 more element

A detection apparatus comprising:

an emitting element;
a receiving element disposed so as to receive at least a portion of an emission from said emitting element and operable to output a detection signal indicative of a detection value corresponding to a parameter prevailing between said emitting element and said receiving element;
and
a controller operable to output a determined value corresponding to the parameter, said controller comprising a parameter arithmetic module operable to convert the detection value to a parameter value, an initial detection value storage unit operable to store an initial detection value, a change ratio arithmetic module operable to arithmetically determine a ratio of change representing a change of the parameter based on the detection value and the initial detection value and a compensation arithmetic module operable to provide a compensating value based on the ratio of change to the parameter arithmetic module,
wherein said parameter arithmetic module is further operable to change the parameter value, based on the compensating value, into the determined value.

2 more elements

Dependencies are inferred from the claim text.