Smoke sensor and monitor control system

• US 6,011,478 A
• Filed: 04/29/1998
• Issued: 01/04/2000
• Est. Priority Date: 05/08/1997
• Status: Expired due to Term

• Current Assignee: LIXIL NITTAN Co., Ltd. (Secom Company Limited)
• Original Assignee: Nittan Co. Ltd. (Old) (Secom Company Limited)
• Inventors: Yamazaki, Ryuichi, Suzuki, Takashi, Yoshikawa, Yuki
• Primary Examiner(s): Lefkowitz, Edward
• Application Number:
  US09/069,086
• Time in Patent Office: 615 Days
• Field of Search: 340/628, 340/630, 250/573, 250/574
• US Class Current: 340/630
• CPC Class Codes: G08B 17/107 for detecting light-scattering due to smoke
• CPC Class Codes: G08B 17/113 Constructional details

Abstract

A smoke sensor includes a light receiving unit for temporally alternately receiving scattered light of two different wavelengths λ₁ and λ₂ ; a calculating unit for performing a calculation required for smoke detection, on a scattered light output y of the wavelength λ₁ and a scattered light output g of the wavelength λ₂ from the light receiving unit; and a smoke detection processing unit for performing a smoke detection process on the basis of a calculation result output from the calculating unit. The calculating unit estimates an output value of one of the scattered light output y of the wavelength λ₁ and the scattered light output g of the wavelength λ₂ at a sample timing of the other output, and obtains a ratio of the estimated output value of the one scattered light at the sample timing of the other output to an output value of the other scattered light, as a two-wavelength ratio.

Claims

1. A smoke sensor comprising:

light receiving means for temporally alternately receiving scattered light of two different wavelengths λ

₁ and λ

₂ ;

calculating means for performing a calculation required for smoke detection, on a scattered light output y of the wavelength λ

₁ and a scattered light output g of the wavelength λ

₂ from said light receiving means; and

smoke detection processing means for performing a smoke detection process on the basis of a calculation result output from said calculating means, said calculating means estimating an output value of one of the scattered light output y of the wavelength λ

₁ and the scattered light output g of the wavelength λ

₂ which are temporally alternately output from said light-receiving means, at a sample timing of the other output, and obtaining a ratio of the estimated output value of the one scattered light at the sample timing of the other output to an output value of the other scattered light, as a two-wavelength ratio.

2. A smoke sensor according to claim 1, wherein said calculating means performs the estimation of the output value of one of the scattered light output y of the wavelength λ

₁ and the scattered light output g of the wavelength λ

₂ which are temporally alternately output from said light receiving means, by performing an interpolation on one of the scattered light output y of the wavelength λ

₁ and the scattered light output g of the wavelength λ

₂.

3. A smoke sensor according to claim 1, wherein said calculating means takes a moving average of each of the scattered light output y of the wavelength λ

₁ and the scattered light output g of the wavelength λ

₂ from said light receiving means, estimates an output value of one of the moving-averaged scattered light output y of the wavelength λ

₁ and the moving-averaged scattered light output g of the wavelength λ

₂, at a sample timing of the other output, and thereafter obtains a ratio of the estimated output value of the one moving-averaged scattered light at the sample timing of the other output to an output value of the other moving-averaged scattered light, as the two-wavelength ratio.

4. A smoke sensor according to claim 1, wherein, after estimating the output value of one of the scattered light output y of the wavelength λ

₁ and the scattered light output g of the wavelength λ

₂ which are temporally alternately output from said light receiving means, at a sample timing of the other output, said calculating means takes a moving average of the estimated output value and a moving average of the output value of the other scattered light, and obtains a ratio of the estimated output value of the one moving-averaged scattered light at the sample timing of the other output to an output value of the other moving-averaged scattered light, as the two-wavelength ratio.

5. A smoke sensor according to claim 1, wherein, after obtaining a ratio of the estimated output value of the one scattered light at the sample timing of the other output to the output value of the other scattered light, as the two-wavelength ratio, said calculating means takes a moving average on the two-wavelength ratio to obtain another two-wavelength ratio.

6. A smoke sensor according to claim 1, wherein, when or after the output value of one of the scattered light output y of the wavelength λ

₁ and the scattered light output g of the wavelength λ

₂ from said light receiving means is equal to or larger than a predetermined value, said calculating means starts the calculation required for smoke detection.

7. A smoke sensor according to claim 6, wherein, when, after the calculation required for smoke detection is started, the output value of one of the scattered light output y of the wavelength λ

₁ and the scattered light output g of the wavelength λ

₂ from said light receiving means reaches an upper limit value, said calculating means holds a calculation result which is obtained immediately before the output value reaches the upper limit value.

8. A smoke sensor according to claim 1, wherein said smoke detection processing means judges a smoke characteristic on the basis of the two-wavelength ratio from said calculating means.

9. A smoke sensor according to claim 8, wherein, when the smoke characteristic is judged, said smoke detection processing means variably sets a fire criterion for each smoke characteristic.

10. A smoke sensor according to claim 9, wherein said smoke detection processing means variably sets a fire level for judging whether a fire breaks out or not on the basis of the largeness of two wavelength ratio.

11. A smoke sensor comprising:

controlling means for controlling a whole of said sensor;

first light emitting means for, when driven by said controlling means, emitting light of a wavelength λ

₁ ;

second light emitting means for, when driven by said controlling means, emitting light of a wavelength λ

₂ ;

light receiving means for receiving scattered light of the light of the wavelength λ

₁ emitted from said first light emitting means, and scattered light of the light of the wavelength λ

₂ emitted from said second light emitting means;

calculating means for performing a calculation required for smoke detection on a scattered light output y of the wavelength λ

₁ and a scattered light output g of the wavelength λ

₂ from said light receiving means; and

smoke detection processing means for performing a smoke detection process on the basis of a calculation result output from said calculating means, said first and second light emitting means being incorporated in a single light emitting device, and the light of the wavelength λ

₁ and the light of the wavelength λ

₂ being emitted from said single light emitting device.

12. A smoke sensor comprising:

controlling means for controlling a whole of said sensor;

first light emitting means for, when driven by said controlling means, emitting light of a wavelength λ

₁ ;

second light emitting means for, when driven by said controlling means, emitting light of a wavelength λ

₂ ;

light receiving means for receiving scattered light of the light of the wavelength λ

₁ emitted from said first light emitting means, and scattered light of the light of the wavelength λ

₂ emitted from said second light emitting means;

calculating means for performing a calculation required for smoke detection on a scattered light output y of the wavelength λ

₁ and a scattered light output g of the wavelength λ

₂ from said light receiving means;

smoke detection processing means for performing a smoke detection process on the basis of a calculation result output from said calculating means; and

light guiding means for guiding the light of the wavelength λ

₁ emitted from said first light emitting means, and the light of the wavelength λ

₂ emitted from said second light emitting means so that the light of the wavelength λ

₁ emitted from said first light emitting means, and the light of the wavelength λ

₂ emitted from said second light emitting means are directed in a same light emission direction.

13. A smoke sensor according to claim 12, wherein said light guiding means is a prism.

14. A smoke sensor according to claim 12, wherein said light guiding means is a branched optical fiber.

15. A monitor control system comprising:

a receiver; and

an analog light scattering smoke sensor which is connected to a transmission path elongating from said receiver and which is monitored and controlled by said receiver,

wherein, when said analog light scattering smoke sensor is a smoke sensor which temporally alternately receives scattered light of two different wavelengths λ

₁ and λ

₂, said receiver comprises;

calculating means for performing a calculation required for smoke detection, on a scattered light output y of the wavelength λ

₁ and a scattered light output g of the wavelength λ

₂ from said light receiving means; and

smoke detection processing means for performing a smoke detection process on the basis of a calculation result output from said calculating means, said calculating means estimating an output value of one of the scattered light output y of the wavelength λ

₁ and the scattered light output g of the wavelength λ

₂ which are temporally alternately output from said light scattering smoke sensor, at a sample timing of the other output, and obtaining a ratio of the estimated output value of the one scattered light at the sample timing of the other output to an output value of the other scattered light, as a two-wavelength ratio.