Santa Barbara Research Center

Hughes Aircraft Company

Kenneth A Shamordola

Mark T Kern

Gregory L Tangonan

John M Wetzork

Steven E Hodges

Danny G Snider

A fiber optic fire and overheat sensor system 10 includes a fiber optic cable 12 having a lens 14 at a distal to direct radiation from a fire 16 into the cable 12 and to a radiation detector 18 disposed at a proximal end of the cable 12. Detector 18 is coupled to a fire sensor 19. The detector 18 is sensitive to two wavelength bands including a short wavelength band of approximately 0.8 to approximately 1.1 microns and a long-wavelength band of approximately 1.8 to approximately 2.1 microns. A controller 21, such as a microprocessor, analyzes the fire sensor 19 output signals which correspond to the two spectral bands to determine if a fire is present. The system 10 further includes a body of fluorescent material 20 disposed at the distal end of the cable 12. The material 20 can be interposed between a reflecting surface, such as a mirror 22, and a lens, such as a collimating lens 24. A fiber optic coupler 26 and 26a launches radiation from a source 28, such as a laser diode, into the fiber optic cable 12. The fluorescent material is pumped by the source 28 at a first wavelength, the rate of decay of a resulting fluorescent emission being measured and correlated with predetermined decay rates to derive the temperature of the material 20 and, hence, the ambient temperature of a region within which the material 20 is disposed.

Fiber optic flame and overheat sensing system with self test

A fiber optic fire detection and temperature measurement system 10 includes a fiber optic cable 12 having a lens 14 at a distal to direct radiation from a fire 16 into the cable 12 and to radiation detector 18 disposed at a proximal end of the cable 12. Detector 18 is coupled to a fire sensor 20. Detector 18 is sensitive to three wavelength bands including a short wavelength band of approximately 0.8 to 1.1 microns, a mid-wavelength band of approximately 1.3 to 1.5 microns and a long-wavelength band of approximately 1.8 to 2.1 microns. A controller 22, analyzes the fire sensor 20 output signals which correspond to the two spectral bands to determine if a fire is present. The fiber optic conductor is doped with a material selected for its temperature dependent fluorescent emission characteristics. Radiation from a fire passes via cable 12 to the detector 18. A pulse of radiation from source 28 passes from a coupler 26 and 26a to the cable 12. The fluorescent doping material within the fiber optic cable 12 is pumped by the pulse and is caused to fluoresce within the third wavelength band. A portion of the fluorescent emission passes back through the fiber 12 to the detector 18 where the fluorescent emission is detected and processed to determine the temperature.

Fiber optic flame detection and temperature measurement system employing

A fiber optic fire detection and temperature measurement system 10 includes a fiber optic cable 12 having a lens 14 at a distal to direct radiation from a fire 16 into the cable 12 and to a radiation detector 18 disposed at a proximal end of the cable 12. Detector 18 is coupled to a fire sensor 20. The detector 18 is sensitive to three wavelength bands including a short wavelength band of approximately 0.8 to 1.1 microns and a long-wavelength band of approximately 1.8 to 2.1 microns. A controller 22, analyzes the fire sensor 20 output signals which correspond to the two spectral bands to determine if a fire is present. The fiber optic conductor of cable 12 includes an optical filter 32 having a temperature dependent radiation transmission characteristic. Radiation from a fire passes via cable 12 to the detector 18. A dual wavelength pulse of radiation from a source 28 passes through the filter 32 where a reference wavelength, corresponding to one of the fire sensor spectral bands, passes through unimpeded while the other wavelength within a third spectral band is absorbed as a function of temperture. The detector includes third element 18c for detecting the third spectral band and includes circuitry 54 for determining the temperature of the coupler 30.

Fiber optic flame detection and temperature measurement system having

Apparatus for sensing the ex(i)stence of a fire and providing a warning, if desired, with improved discrimination against the possibility of false alarms. Dual channel detectors are used, one detector being set to respond to incident radiation having a wavelength in the range of 0.8 to 1.1 microns while the other wavelength range is significantly displaced therefrom, being selected for wavelengths in the range from 14 to 25 microns. Reliability of true signal detection is further improved by the provision of separate flame flicker bandpass filters in the respective channels, these bandpass filters being set for different passbands. Circuits providing ratio discrimination, threshold detectors and delay circuitry are combined with the dual spectrum detectors and disparate flicker frequency filters to achieve improved performance. In addition, the dynamic range of instrument sensitivity is substantially increased by utilizing preamplifiers with wide gain variability controlled by automatic gain control circuits in the dual channel circuitry.

Dual spectrum frequency responding fire sensor

A fire sensing system utilizing fiber optics to extend the physical range of radiation sensing elements into areas and environments which are physically inaccessible to, and/or destructive of, such sensors and their associated electronic circuitry. The fiber optics are combined with signal processing circuitry to achieve reliable fire sensing systems which present particular advantages in special applications.

Fire sensor system utilizing optical fibers for remote sensing

Apparatus for sensing the existence of a fire and providing a warning, if desired, with improved discrimination against the possibility of false alarms. Dual channel detectors are used, one detector being set to respond to incident radiation having a wavelength in the range of 0.8 to 1.1 microns while the other wavelength range is significantly displaced therefrom, being selected for wavelengths in the range from 14 to 25 microns. Reliability of true signal detection is further improved by the provision of separate flame flicker bandpass filters in the respective channels, these bandpass filters being set for different passbands. Circuits providing ratio discrimination, threshold detectors and delay circuitry are combined with the dual spectrum detectors and disparate flicker frequency filters to achieve improved performance. In addition, the dynamic range of instrument sensitivity is substantially increased by utilizing preamplifiers with wide gain variability controlled by automatic gain control circuits in the dual channel circuitry.

Circuitry for using the statistical properties of detected radiation in the time domain to discriminate between stimuli from fire and non-fire sources. Statistical discriminators for fire sensing may be combined with other types of sensors operating in the frequency domain for developing improved sensitivity with better security against false alarms. Such other types of sensors may include peak detectors, zero crossing detectors, second derivative-equal-to-zero detectors, for example. The invention determines the mean or average, the variance or standard deviation, the mean deviation, and the Kurtosis of sampled data in statistical analysis to discriminate between fires and non-fires.

Fire sensor statistical discriminator

A cross-correlation fire sensor circuit includes detectors responsive to heat and light radiation, respectively. Electrical signals from the detectors are processed in two distinct channels through low pass filters and samplers. The sampled signals from the two channels are multipled together and the products are summed over a selected interval to provide a correlation function. This function is compared with an adjustable threshold to provide an indication of fire sensing. The circuit is also included as an adjunct to an existing system to provide improved sensitivity for fire sensing in the presence of noise and enhanced discrimination against false alarms. A ratio window detector circuit is disclosed as an alternative cross-correlator for detected radiation.

Growing community of inventors

Santa Barbara, CA, United States of America

Kenneth A Shamordola