Flame and smoke detector

• US 6,111,511 A
• Filed: 01/20/1998
• Issued: 08/29/2000
• Est. Priority Date: 01/20/1998
• Status: Expired due to Fees

• Current Assignee: Purdue Research Foundation (The Trustees of Purdue University (d/b/a Purdue University))
• Original Assignee: Purdue Research Foundation (The Trustees of Purdue University (d/b/a Purdue University))
• Inventors: Gore, Jay P., Sivathanu, Yudaya, Lloyd, Andrew, Tseng, Likeng, Joseph, Rony K.
• Primary Examiner(s): Wu, Daniel J.
• Assistant Examiner(s): PHAM, TOAN NGOC
• Application Number:
  US09/009,054
• Time in Patent Office: 952 Days
• Field of Search: 340/577, 340/578, 340/628, 340/629, 340/630, 250/339.05, 250/338.1, 250/554, 250/336.1, 250/339.01, 250/339.02, 250/339.08, 250/339.15, 250/340, 250/372
• US Class Current: 340/577
• CPC Class Codes: G08B 17/12 Actuation by presence of radiation or particles, e.g. of infrared radiation or of ions

Abstract

A fire and smoke detector utilizes a statistical analysis of the near infrared radiation incident on it. The spectral radiation intensities incident on the fire detector are continuously measured at two near-infrared wavelengths, and a time series of apparent source temperatures is obtained from these measurements. The power spectral density and the probability density function of the apparent source temperatures are sufficient to determine the presence of a fire in the vicinity of the detector. The detector can indicate the presence of a fire in an adjoining room from the radiation which is incident on it due to reflections from common building materials. The present invention relates to fire and/or smoke detection methodology and associated apparatus. The detector utilizes fiber optic as a viewing and absorption/scattering detection means.

Claims

1. A smoke and flame detector comprising:

first and second photo-detectors operational within a near-infrared spectrum;

first and second optical filter means coupled to said first and second photo-detectors respectively;

an analog to digital (A/D) converter operatively coupled to said photo-detectors;

a microprocessor operatively coupled to said A/D converter wherein said microprocessor further comprises light intensity value conversion and sampling means for converting light intensity input from said A/D converter to values in a near-infrared spectrum range and sampling said values for a predetermined period;

memory means for storing information, said memory means coupled to said microprocessor and said A/D connector, wherein said memory means stores intensity values obtained from a predetermined sampling period and said detector utilizes said stored values to determine temperature PDF and noise normalized power special density;

first and second photo-diodes;

a digital to analog (D/A) converter operatively coupled to said photo-diodes;

said microprocessor operatively coupled to said first and second photo-diodes and said D/A converter;

a plurality of light sensing means for receiving light from at least one of said first and second diodes and passing the received light to said microprocessor;

at least one of said light sensing means comprising a light absorption detection means for providing information to said microprocessor relating to the intensity of received light;

at least another of said light sensing means comprising a scattered light detection means coupled to said microprocessor for receiving scattered light and passing the received scattered light to said microprocessor;

wherein each said photo-detector, photo diode, light sensing means, and optical filter means comprises a calibration constant; and

wherein a noise normalized ration E_N (f) output is calculated using;

##EQU6## where E(f) is the power spectral density of voltage, intensity, or temperature, and S(f) is the power spectral density of random noise which is constant for a fixed sampling frequency.

2. The smoke and flame detector of claim 1 wherein at least one of said light absorption detector means and said scattered light detection means comprises an optic lens.

3. The smoke and flame detector of claim 1, wherein at least one said light sensing means comprises optic fiber.

4. The smoke and flame detector of claim 3, wherein said optic fiber is comprised of plastic.

5. The smoke and flame detector of claim 4 wherein said optic fiber is comprised of plastic.

6. The smoke and flame detector of claim 1 wherein said scattered light detection means comprises optic fiber.

7. The smoke and flame detector of claim 6 wherein said optic fiber is comprised of plastic.

8. The smoke and flame detector of claim 1 wherein said light absorption detection means comprises optic fiber.

9. The flame and smoke detector of claim 1, wherein said storage means comprises information relating to said calibration constants.

10. The flame and smoke detector of claim 1, wherein said microprocessor, utilizing said stored intensity values calculates an incident radiation field in accordance with a detected radiation intensity I.sub.λ

1 =C₁₁ V₁ where V₁ is the voltage on the first photo-diode and C₁₁ is said calibration constant and wherein a detected radiation intensity I.sub.λ

2 =C₁₂ V₂ where V₂ is the voltage on the second photo-diode and C₁₂ is a calibration constant.

11. The flame and smoke detector of claim 10, wherein said microprocessor determines a probability density of a flame source temperature over a plurality of sample points in accordance with

12. The flame and smoke detector of claim 11, wherein said determined temperature is stored in said memory means.

13. The flame and smoke detector of claim 11, wherein at least one of said temperature sample points falls within a range of temperatures that ranges between approximately 700K and 2500K.

14. The flame detector of claim 1, further comprising a low pass filter, whereby said white noise is low pass filtered at a frequency of M/2.

15. The flame detector of claim 14, wherein said low pass filtered white noise comprises a uniform value 2/M between zero and M/2, and said value is approximately zero at other frequencies.

16. A flame detector of claim 1 wherein a fixed level of E_N (f) is used to indicate the existence of a fire.

17. The flame detector of claim 1 wherein a ratioed power spectral density E_R (f) is calculated in accordance with ##EQU7## where f_1L is a first lower frequency ranging from 0 to 50 Hz, f_1H is a first higher frequency greater than f_1L, f_2L is second lower frequency ranging from 0 to 50 Hz, and, f_2H is a second higher frequency greater than f_2L.

18. The flame detector of claim 17 wherein the value of E_R (f) indicates the existence of a fire.

19. A method of detecting a flame comprising the steps of:

recording the level of background radiation;

detecting at least one source of radiation having a frequency within the near infrared spectrum;

sampling the detected radiation for a predetermined period;

calculating a series of radiation temperatures in real time to determine an incident radiation field;

generating a probability density function (PDF) for one of an incident radiation field, a temperature and a voltage level;

calculating a power density for said PDF comparing the recorded background radiation with the calculated power density to yield a value; and

providing an alarm indication when said value exceeds a predetermined level.