DK176996B1 - Fire detection system and method for early fire detection - Google Patents

Abstract

A fire detection system (16) of method serves for early fire detection. The system is of the kind comprising a first radiation-sensitive semiconductor (22a, 35a) for measuring a first radiation intensity at a first wavelength and emitted from a region susceptible to fire, and forming a first output signal representing the first radiation intensity, and at least one other radiation-sensitive semiconductor (22b, 22c, 35b, 35c) for measuring at least one other radiation intensity at at least one other wavelength and emitted from the region susceptible to fire and creating a second output signal representing the second radiation intensity. The fire detection system (16) comprises that the first radiation-sensitive semiconductor (22a, 35a) and the at least one other radiation-sensitive semiconductor (22b, 22c, 35b, 35c) are arranged in a predefined pattern, that the fire detection system (16) has means for converting it first output signal for a first temperature indicating signal and the at least second output signal for at least a second temperature indicating signal, processing means for comparing the first temperature indicating signal with the at least second temperature indicating signal serving as a control for the first temperature indicating signal, a database (21) including ignition data for materials on a flammable fire target, and comparison means for comparing the temperature indicating signals with the database.

Description

DK 176996 B1 i

The present invention relates to a fire detection system of the kind comprising a first radiation sensitive semiconductor for measuring a first radiation intensity at a first wavelength and emitted from a region susceptible to fire and emitting a first output signal representing the first radiation intensity. and at least one other radiation-sensitive semiconductor for measuring at least one other radiation intensity at at least a different wavelength and emitted from the fire susceptible region, and emitting at least one other output signal representing the second radiation intensity.

Fires occur when both combustible and / or flammable material with a sufficient supply of oxygen or another oxidizing agent is exposed to sufficient heat. Some 15 common fire-causing heat sources include, for example, a spark, another fire, such as an explosion, a cigarette, or a lit match, heat radiation, such as sunlight, an exhaust duct, white-hot electric bulb, or a radiator.

20

Mechanical and electrical machinery may cause fire if flammable materials used on or located near the equipment are subject to intense heat. Fire can spread to an uncontrolled level and cause great harm to and destroy human life, animals, plants and property. Consequently, a fire can incur significant costs, harmful to the environment and society, and must be detected as early as possible to avoid and avert such damage and unwanted side effects.

30 Often, overheated places are not recognized until it is too late, and the fire develops to the above stages, causing considerable damage.

Conventionally used technologies to recognize the fire's 35 early attacks include live videos from the fire and exact long-range temperature measurement to save time and increase the reliability and safety of early fire detection.

Almost all objects or surfaces emit 5 electromagnetic radiation, the intensity and spectral distribution of which depends on the temperature of the body. Detectors for the near-infrared (NIR) spectral range from 750nm to 3000nm can detect heat radiation from temperatures of about 300 ° C on surfaces. NIR radiation is reflected by most surfaces, 10 and direct vision of the flames is not necessary. For example, NIR radiation is reflected or scattered using aerosols such as fog, smoke and dust. Therefore, in many situations, open fire can be located through smoke.

15 This temperature is far below the limit at which the human eye can see radiation, the spectral range of visible light (VIS) within about 400 nm to 750 nm of the electromagnetic spectrum, against which the retina is sensitive. Open fire also emits in this area and 20 low cost late detection alarm systems are easy to develop in this wavelength range.

To look at wavelengths that are even longer than NIR

the spectral range, such as mid-infrared (MIR) 3μιη to 30μτη, allows even lower temperatures to be detected. In this way, potential fire sources can be detected long before they burst into open flames.

Using known camera-based fire monitoring based on NIR video images and processing, each pixel in an image is identified and used to accurately locate the potential source of fire. Thermography in the NIR is used to provide temperature measurements of each pixel within the video image. The displayed object is presented with accurate 35 temperature values for each point on the surface, and this information helps to detect the origin of the fire before the flash point temperature is reached and therefore to prevent fire. The image capture takes place in a wavelength range invisible to the human eye and the image is transferred to a black and white video. Areas of unusual activity, which may cause alarm, are highlighted with special colors to simplify the incomprehensible assessment situation. For the detection of aerosols, the experienced observer can decide whether it is smoke, fog or dust based on evolution over time. Based on video images, precise localization within a 3D 10 space is possible. In the case of a known topography, the distance to the observed surface can be determined since the direction of each pixel within the viewing angle is known. With a fixed installation of the monitoring system, only one camera is needed for precise location. This is mandatory for a targeted 15 situational assessment and commencement of firefighting activities. If the fire source is detected by two cameras at the same time, the exact location is possible without further information. Therefore, localization in three dimensions is possible even with moving objects within the surveillance area when several cameras are used.

Using thermography combined with video images has many advantages. It ensures clear vision through thick smoke and allows for the search and rescue of humans, as well as safe temperature measurement of objects close to the fire, however, the technique requires constant day-and-night monitoring to spot abnormalities and deviation from standard conditions, to safely distinguish between false temperature fluctuations and movements.

If the observing person is inattentive just for a short 30 period or is not sufficiently qualified to read the images, the fire may develop anyway.

Artificial light, sunlight, controlled sources of fire, such as lighters or bunsen burners, industrial ovens, arc welds, 35, etc. emit in the IR range and can cause false alarms.

DK 176996 B1 4 US patent no. 5,995,008 discloses a fire alarm for measuring a spectrum from a fire by means of two light meters sensitive in each spectrum.

U.S. Pat. 6,927,394 discloses a method for detecting flames. The method utilizes false-alarm sources to emit radiation in both the infrared and the visible wavelength range, while potential fire sources emit only in the visible wavelength range. If radiation is present in both the 10 infrared spectral range and the visible spectral range, it is interpreted as a false alarm. The method involves comparing the measured frequency spectra and known reference spectra from potential fire sources and radiation from false-alarm sources. The method generally monitors potential fire sources in a 15 zone and uncritically activates a fire extinguishing system which, for example, sprinkles extinguishers throughout the area. In addition, all machinery is turned off, resulting in unnecessary damage to the machines, longer shutdown times of production, 20 resulting in high costs. Only the temperature is measured, and this known method does not provide any measurements which provide sufficient knowledge to enable targeted and specific early fire extinguishing using fire extinguishing agents particularly suitable for the purpose.

25

As a result, there is a need in the field of fire detection technology to provide alternative and safe measures for early fire detection.

In a first aspect of the present invention, there is provided an early fire detection method and system of the type mentioned initially by which improved security and great cost savings can be achieved.

In another aspect of the present invention there is provided an early fire detection method and system of the kind mentioned above, which provides a high level of identification precision of the combustible and / or flammable material.

In a third aspect of the present invention there is provided an early fire detection method and system of the kind mentioned initially by which false alarms can be excluded to a greater extent than hitherto known.

In a fourth aspect of the present invention, there is provided an early fire detection method and system of the kind mentioned above, which can be adapted to a specific environment based on prior knowledge of the compositions of materials used in the environment.

In a fifth aspect of the invention, there is provided an early fire detection method and system of the kind mentioned above, in which countermeasures against fire can be initiated faster and far more targeted than hitherto known.

In a sixth aspect of the present invention, there is provided an early fire detection method and fire detection system wherein information on the material of fire 25 is provided to the fire crew prior to the commencement of the fire extinguishing.

The new and distinctive features thereby achieved in accordance with the present invention consist in the fire detection system 30 comprising the first radiation-sensitive semiconductor and the at least one second radiation-sensitive semiconductor being arranged in a predefined pattern that the fire detection system has means for converting the first output signal for a first temperature indicating signal, and the at least second output signal 35 for at least a second temperature indicating signal, processor means for comparing the first temperature indicating signal with the at least second temperature indicating signal, which second temperature indicating signal serves as a control for the first temperature indicating signal, a database including 5 ignition data for materials on a susceptible fire target, and comparison means for comparing temperature indicating signals with the database.

An optical system reproduces the zone of the radiation-sensitive semiconductors, so that each region of the zone corresponds to a radiation-sensitive semiconductor or more.

Since the position of the radiation-sensitive semiconductors of the present invention is arranged in a defined pattern, the regions that the radiation-sensitive semiconductors monitor are also well defined. Two radiation sensitive semiconductors are selected to monitor and detect at two different wavelengths radiated from the same region and the results are compared to confirm whether the detection is either false 20 alarm or a true alarm. Two radiation-sensitive semiconductors located at different locations in the pattern will monitor different areas in, for example, a room or an open space. When a potential fire source occurs in the area within a monitoring area of one of the radiation sensitive semiconductors, it will send an alarm signal so that the fire extinguishing system can focus its resources solely on that area. For example, if fire extinguishing is sprinkled, it is only sprinkled in that area and only electricity and heat sources, such as machinery, are extinguished in that area. In this mode of invention, damage and drying operations can be significantly reduced compared to a situation where fire extinguishing is sprinkled over an entire machinery park. Production can resume early, repair costs are low, and income reductions remain at a minimum. It is even possible to continue the production line despite the incident in part of the zone, which is not close to the incident, which further minimizes financial losses.

Within the scope of the present invention, the term black body means hereinafter an object which absorbs all electromagnetic radiation which falls onto it. No radiation passes through it and none is reflected, making black bodies the ideal heat radiation source. The amount and spectrum of electromagnetic radiation that they emit is directly related to their temperature. Black bodies below about 430 ° C produce very little radiation at visible wavelengths and appear black. Black bodies above this temperature produce radiation at visible wavelengths starting at red, going through orange, yellow and white before ending up at blue as the temperature rises.

So a body emits broadband radiation due to its temperature, so-called black body radiation, the hotter the object the higher the radiation. The radiation center is also shifted 20 toward blue at higher black body temperature. The intensity of a radiation sensitive semiconductor that responds to a known wavelength from a black body can be transformed to a temperature which is the temperature of the black body. Another radiation-sensitive semiconductor, which measures at a different wavelength, will detect a different intensity, but when transformed to temperature, it will indicate the same temperature unless the recorded measurement is not from a blackbody or there is a defect in the fire detection system.

The air absorbs radiation at some IR wavelength ranges.

This must be taken into account when choosing the measurement wavelengths, ie. the first wavelength and the at least one second wavelength. A radiation sensitive semiconductor that measures the radiation from an object at a wavelength at which air absorbs will return an output signal corresponding to a temperature too low. Therefore, the wavelengths at which the radiation-sensitive semiconductors respond must be chosen in the region where the gas molecules in air do not absorb.

If the two radiation-sensitive semiconductors indicate the same temperature, the temperature is compared with the known ignition temperature of the material in the monitored zone, area or room. A temperature, for example 200 ° C, is critical if the object is paper, while there is no need to send an alarm signal if a piece of metal has reached the temperature.

In an advantageous embodiment of the present invention, the pattern may be selected from the group consisting of a 2-dimensional array, a 3-dimensional array, concentric circles, polygons or any order. How the radiation-sensitive semiconductors are organized is less important as long as their positions within the pattern are known along with information from which area each radiation-sensitive semiconductor detects radiation.

In a preferred embodiment of the invention, the radiation sensitive semiconductors may be selected from the group comprising photodiodes, PIN diodes, CMOS circuits, bolometers or CCD chips and combination thereof. Anything that is photosensitive can be used, such as photo diodes such as PIN diodes. In a 25 photosensitive CMOS, the photodiodes are arranged in advance in a defined array where the amount of radiation reaching each photodiode can be read out. If a very high level of detection is required, a liquid nitrogen-cooled CCD chip is especially preferred.

30

The inventive fire detection system is particularly suitable for the use of radiation sensitive semiconductors which can measure in the wavelength range from approx. 200nm to approx. 3,500nm. To detect the potential source of fire early is MIR

35 spectral range from 3μιη to 30μπι most suitable. But to avoid the air absorbing some of the radiation, it is better to measure DK 176996 B1 9 in the wavelength range between 8μιη and 14μιη. There are other sources that emit radiation in this spectral range without being potential sources of fire, such as artificial light, sunlight, lighters or Bunsen burners, industrial ovens, welding arc lights, etc. In Appendix 5, these potential sources of radiation also emit radiation in the visible spectral range. A detector that responds to a wavelength in the visible spectral range from 400nm to 750nm can determine that it is not a potential source of fire since it emits in both mir and visible range. If the 10 fire detection system is to monitor a very well-lit zone or outdoor location on a sunny day, visible radiation from a false-alarm source is drowned by the visible background radiation. To filter out a welding arc as a false-alarm source, it is better to use a radiation sensitive 15 semiconductor that responds to a wavelength in the ultraviolet (UV) spectral range from 200nm to 400nm, since such an arc is a strong UV radiation emitter. In many factory zones fluorescent lamps are used as information. They emit relatively little radiation in the infrared area. In a 20 zone that is highly illuminated with fluorescent lamps, radiation sensitive semiconductors used for reference and control can advantageously be selected to respond to radiation in the NIR spectral range from 750nm to 3000nm.

Preferably, the means for converting an output signal to a temperature indicating signal, the processor means and the comparative means may include a control unit in the form of, for example, a microprocessor, a user programmable gate array (FPGA) or a programmable logic control unit (PLC) and suitably designed software programs. The control unit and software programs are designed and configured to process the output signal from the radiation sensitive semiconductors which convert the output signal to a temperature indicating signal, compare the temperature indicating signals, and to retrieve data regarding the location in the zone of various materials and the ignition temperature of the material. the monitored area to compare the temperature indicating signal and the ignition temperature of the material in the monitored area and respond to the result by issuing an alarm.

5

The fire detection system may comprise at least one gas detector in a preferred embodiment of the present invention. The system is similar to that of the fire detection system.

An optical system reproduces different regions of the zone up to 10 on the photoactive components which are radiation sensitive semiconductors organized in a known pattern as an array. In a first embodiment, the gas detector uses the black body radiation from the background, such as the walls, floor and the machines, as a radiation source. If a gas is developed, for example due to heated plastic, the gas molecules from the plastic will absorb at some wavelengths characteristic of the gas molecules.

In yet another preferred embodiment, the database 20 of the fire detection system may include data representing the wavelengths at which at least some gases absorb radiation. The database enables the specification of the heated gas molecules. The database may further comprise detailed information on where said plastic molecules originate. If the temperature in the region of the heated plastic is also measured, it is possible to determine how close to the ignition point the temperature is. For example, if the wavelengths of CO are recorded in the database, the gas detector can send an alarm that there is toxic gas in the zone. Especially for CO it may be 30 important as it does not smell. Other important gases may include the gas dioxin.

The fire detection system may advantageously comprise an external radiation source. The detection limit will increase so that lower concentrations can be detected.

DK 176996 B1 11

If there is more than one gas detector and they are located in two different locations, they will look over each other and the system can reproduce a three-dimensional image of the distribution of gases in e.g. a monitored zone, room or area.

In one embodiment of the invention, the fire detection system may comprise a spark detector having a response time faster than or about 8 ms and having a sensitivity lower than or about 1.1 mW / cm 2. To detect the sparks, only 10 are possible to monitor closed environments where there is no external light. In such an environment where dry materials are transported, an ignition detector is applicable. The woodworking industry, where sawdust or wood shavings are sucked up in transport pipes, is one example. In all forms of material processing, dust is formed which can be ignited by a spark. This is the case in the steel industry and in the paint-painting industry. Spray liquids with a low ignition temperature can easily be ignited by a spark.

Such an environment can be found in the painting industry, the printing industry, petroleum refining, semiconductor production, etc. What is most important is that the fire detection system of the present invention reacts really quickly. Therefore, it is preferred to keep electronic analyzes simple and fast, in order to increase the reaction time. This further means that there is no time for detailed investigation as to whether the fire alarm is due to a false-alarm source. The spark detector can advantageously consist of many radiation sensitive semiconductors which monitor different areas of the zone or area that is fire susceptible. Only machines in the 30 range corresponding to the radiation-sensitive semiconductor that send an alarm are shut down, and fire extinguisher is sprinkled only in this same area. In this way, damage and production losses are kept low. This can be a huge benefit if there are many false alarms.

In another embodiment of the invention, the fire detection system may comprise a smoke detector. The smoke detector reads the signal from a radiation source. A radiation source is located at each area which is monitored by a radiation sensitive 5 semiconductor. If smoke starts to develop in such an area, the smoke will disperse and absorb the radiation until there is no light entering the smoke detector. Again at the fire detection system where the potential fire source is located and the fire protection measures can be located.

In yet another embodiment of the invention, the fire detection system may comprise a temperature sensor. The temperature sensor may e.g. be a bolometer.

The invention also relates to a method of detecting fire using the fire detection system of the present invention.

The method comprises the steps of storing ignition temperatures in at least some materials located in a region susceptible to fire in a database of a control unit, measuring radiation intensity from at least one point in the region at a first specified wavelength with a first radiation sensitive semiconductor returning a first output signal, measuring radiation intensity from at least one first point in the range by converting at least one other radiation sensitive semiconductor which returns at least one second output signal, the converted first output signal from the first 30 radiation sensitive semiconductor measured at the first wavelength to a first temperature indicating signal, to convert the at least second output signal from the at least one other radiation sensitive semiconductor measured at least one second wavelength to at least a second temperature indicating signal, to compare d a first temperature indicating signal with the at least one second temperature indicating signal, and determining a first difference value, and if the first difference value is less than a first predefined difference value, compare the first temperature indicating signal with the ignition temperature of the database for the material in the monitored area, 5 and another difference value is determined and if the second difference value is below another predefined difference value an alarm signal is sent.

Using these steps, it is possible to detect fires at a very early stage and to target the fire extinguishing procedure to the materials and compositions located in a specific zone. When the warning or alarm is sent to the fire station, it is possible for the firefighters to take specific precautions regarding fire extinguishers and clothing prior to departure from the fire station. Therefore, it is possible for firefighters to prepare for the fire by using the inventive, goal oriented, effective fire extinguishing method above.

In the preferred embodiment, the first predefined difference value is chosen to be lower than or about 10 ° C. This temperature has been set as the lower limit, which defines a reasonable threshold for false alarms.

In a modified convenient embodiment, the method of the present invention is specifically intended to treat fires involving combustible gases or gas-related evolution.

For this aspect, the method comprises the steps of a control unit database storing absorption wavelengths for a large number of gas molecules, measuring radiation intensity from at least one zone in the region of at least one absorption wavelength for the at least one monitored gas molecule with a first radiation-intensive semiconductor returning an absorption output signal, measuring radiation intensity from the at least one zone in the region of at least one non-absorption wavelength of the at least one monitored gas molecule with at least one other radiation-sensitive semiconductor returning at least one non-absorption output signal, comparing it at least one absorption output with the at least one non-absorption output signal and determining whether there is a difference between the at least one absorption output signal and the at least one non-absorption output signal due to absorption, and to send an alarm signal if the difference is due to absorption.

Advantageously, the method may further comprise the step of converting the temperature corresponding to the first temperature indicating signal to an intensity for measuring at least one absorption wavelength of at least one gas molecule to a first database intensity, the radiation intensity of the at least one region of the zone at least one absorption wavelength of the at least one monitored gas molecule with at least one other radiation-sensitive semiconductor returning at least one absorption output signal, comparing the at least one absorption output signal with at least one first database intensity, and if the ratio of the absorption output signal to the first wavelength database intensity characteristic of at least one gas molecule is 25 less than a third predefined ratio value, so send an alarm signal.

Applying the procedure minimizes the risk of explosion and the person being poisoned by gas formation. Again, the 30 firefighters have the opportunity to take precautions, and the gas can even be recognized at such an early stage that no fire occurs at all.

This part of the invention can advantageously be used in 35 manufacturing processes in which undesirable gases may develop during the manufacturing process.

DK 176996 B1 15

The invention will be explained in more detail below, descriptive preferred embodiments with reference to drawings in which: 1 shows the black body radiation from two bodies at 37 ° C and 100 ° C, respectively; 2 shows the transmission of radiation through air; FIG. Figure 3 is a schematic block diagram of a first embodiment of a fire detection system according to the present invention; 4 shows a detailed circuit of a portion of the hardware for the preferred embodiment of a fire detection system according to the invention.

FIG. Figure 1 illustrates two black body radiation curves from two 20 different bodies. Curve 1 and curve 2 show the spectral radiation intensities from two different bodies at 37 ° C and at 100 ° C, respectively, as a function of wavelengths.

Curve 1 and curve 2 are similar in appearance, but curve 1 has its maximum radiation at about 9000nm, whereas curve 2 is offset 25 slightly toward blue with a maximum of approx. 7500nm. The radiation intensity of curve 2 is higher in the whole spectral range than the radiation intensity of curve 1.

Planck's radiation law describes the radiation intensity of a black body as a function of wavelength and temperature:, 2he1 1 1 ~~ p --- ΊΓ- (I) em -1 where h is Planck's constant, c is the speed of light, λ is the wavelength, k is Boltzmann's constant and T is the temperature.

From formula (I), it follows that the radiation ε from a body of an even higher temperature will show a spectrum with a maximum further offset to blue, where the radiation intensity is higher for all wavelengths. At a given wavelength, Planck's radiation law relates the intensity of the emitted radiation from a material to a given temperature, so the measurement of the intensity at a given wavelength determines the temperature.

In vacuum, the radiation intensity emitted from a black body will be the same as the measured radiation intensity over the entire wavelength range. However, in air, the gas molecules in air will absorb radiation at some wavelength ranges shown in FIG. 2. There is a first absorption peak 3 or dive in the transmission spectrum at about 1.3 μηι, a second absorption peak 4 at about 1.9 μιη, a third absorption peak 5 at about 2.7 μιη, a fourth absorption peak 6 at about 4, 4 μηι, a fifth absorption peak 7 at about 5.8 μηι and a sixth absorption peak 8 at about 6.7 μιη. The fifth 7th and sixth 8 absorption peaks overlap and form a total absorption band 9. Between these absorption peaks 25 3,4,5,6,7,8 or dives in the transmissions, there are in the IR range of wavelengths up to 14 μιη, six regions where the absorption of air is low. The widest range 10 is between 8 μηι and 14 μιη.

A second interval 11 with low air absorption is identified from 4.8 μιη to 5 μιη, a third 12 from 3.2 μιη to 4.1 μιη, a fourth 30 13 from 2 μιη to 2.3 μιη, a fifth 14 from 1, 5 μιη to Ι, δμπι, and a sixth 15 from 0.750 μιη to 1.1 μιη. The limit of 0, 750 μηι is not due to absorption, but due to the visible area starting. Only in the wavelength ranges 10 to 15 does the measured intensity at a given wavelength determine the temperature.

DK 176996 B1 17

Fig. 3 is a block diagram of a preferred embodiment of a fire detection system 16. Upon installation, a computer (not shown) communicates electronically with control unit 19 via the programming interface 17 and 5 with the control unit 19. The programming interface could in another embodiment be wireless. Data is loaded into the computer and transmitted via the programming interface 17 and electronic connection 18 to the control unit 19, which stores data for use in the 10 inventive method in a working memory (RAM) 21. The data includes, among other things, the type and distribution of materials in the monitored zone, in in particular, the ignition temperatures of said materials, the zone ranges monitored by the radiation-sensitive semiconductors, the radiation wavelengths to which each 15 radiation-sensitive semiconductors respond, and a first predefined difference value as well as a second predefined difference value identifying relevant materials. The significance of the first predefined difference value and second predefined difference value is explained in a further 20 details below. From the database 20, the controller 19 retrieves data on ignition temperatures of materials in the monitored zone. The ignition temperature of the materials in the monitored zone and the distribution of materials in said zone are collectively referred to in the following detailed description as "first 25 database data". It is by no means intended to limit the understanding that many more data are included in the database.

If the materials in the monitored zone change, for example, by introducing new machines, or an additional pattern, f.

30, for example, an array of radiation-sensitive semiconductors is introduced, this data is loaded into the computer and transmitted via the programming interface 17 and electronic connection 18 to the controller 19 which stores the new information in the RAM 21.

A sensor unit 22, which includes three radiation-sensitive semiconductors 22a, 22b and 22c, responds to radiation by transmitting electrically analog output signals through the electrical connections 23a, 23b and 23c to the A / D converter 24, which, if preferred , can be arranged in the control unit 19.

The current magnitudes of the output signals measure the intensity of the radiation at the measured wavelengths. A / D

the inverter 24 converts the analog output signals into digital output signals and transmits them via electronic connections 27a, 27b and 27c to the control unit 19.

The control unit 19 comprises means (not shown) for converting the digital output signals into digital temperature indicating signals. The control unit 19 retrieves information on what wavelengths each radiation-sensitive semiconductors 22a, 22b and 22c respond to. The controller 19 stores the digital temperature indicating signals in the RAM 21.

The digital temperature indicating signals and from which areas each digital temperature indicating signal is measured are referred to in the following description "first measured data".

The control unit 19 comprises means for comparing the 20 digital temperature indicating signals converted from the digital output signals measured with different radiation sensitive semiconductors at different wavelengths but at the same range.

25 According to Planck's radiation law (I), the temperature should be the same. If the difference in the digital temperature indicating signals from the measurements in the same range is less than the first predefined difference value, radiation is due to black body radiation and the measured temperature is considered to be the body temperature. This means that the measured temperature can be compared with e.g. ignition temperature. If the difference is greater than the first predefined difference value, the radiation is partly caused by radiation that is not from a black body or an error has occurred in the measurements or in the signal processing. Measurements from this area are not taken into account until the measurements indicate DK 176996 B1 19 radiation from a black body. A message or error message, warning or alarm can be triggered according to the factual needs and circumstances.

The control unit 19 comprises means for comparing the first measured data and the first database data, thereby comparing temperature in a range of the first measured data with the ignition temperature of the material in the range of the first database data. If the difference is not less than the other 10 predefined difference value for the material, the situation is not interpreted as threatening and no action is taken.

If the difference between temperatures is less than the other predefined difference value for the material, an alarm signal is sent. The alarm signal is sent via the electronic connection 25 to an alarm diode 26, which may be a light emitting diode. An alarm signal is also transmitted via bus 28 to an external fire alarm or to a fire extinguishing system which will turn off the electricity and machinery located in the area, and e.g. sprinkle fire extinguishing agent in the area.

Both the electronic connection 25 and the bus 28 can be wireless connections.

The address of the fire detection system 16 is manually set from the outside of the fire detector via dipswitch 29 in connection with the 25 control unit 19 via electronic connection 30. A power supply 31 supplies the control unit 19 via electrical connection 32.

In one embodiment, the function dipping switch 33 is used to manually change the function of the fire detection system to a gas detection system or to a smoke detection system.

The function dipping switch is connected to the control unit 19 via electronic connection 34.

35 If the fire detector is used as a gas detector, the procedure is similar to the procedure described for the fire detector.

DK 176996 B1 20

The gases can e.g. be part of or used during a production, processing or processing in the industry, if something in the production, processing or processing goes wrong, or is formed during burning of materials in the supervised room. Measured gas identification data is loaded into the computer and transmitted via the programming interface 17 and electronic connection 18 to the controller 19, which stores the data in a RAM 21 located in the controller. There are also data identifying the areas of the monitored space that the 10 radiation-sensitive semiconductors monitor, which radiation wavelength each radiation-sensitive semiconductor responds to, and the first predefined difference value and a third predefined difference value. The significance of the third predefined ratio value is explained below. From the 15 database, the controller 19 retrieves absorption wavelength data for gases to be monitored in a manner similar to that described above for the fire detection system.

It is important that some of the radiation-sensitive semiconductors are chosen to have response wavelengths at the absorption wavelengths of the gases studied and others are chosen not to have response lengths at the absorption wavelengths of these gases. Walls, floors, ceilings and machines, etc.

25 emits all room temperature black body radiation. Curve 1 of FIG.

1 illustrates the spectral distribution of the radiation at about room temperature. Of course, if the machines are hot, the machines will emit a blackbody radiation that is more intense and more offset to blue.

30 When a gas occurs in a monitored room, it will be seen as dives in the blackbody radiation spectrum from the objects behind the gas seen from the detector. The wavelengths of the dives are the characteristic wavelengths of the gas absorption peaks. The relative size of the dives in the blackbody radiation spectrum corresponds to the relative heights of the different absorption peak points and 2l DK 176996 B1 can be used to further confirm the presence of the gas.

The radiation sensitive semiconductors 22a, 22b and 22c respond

5 on radiation by transmitting electrically analog output signals through electrical connections 23a, 23b and 23c to A / D

inverter 24, in the present embodiment located in the control unit 19. The current magnitudes of the output signals are measures of the radiation intensity at the measured wavelengths. The A / D 10 converter 24 converts the analog output signals into digital output signals and transmits them via electronic connections 27a, 27b and 27c to control unit 19.

The control unit 19 retrieves information at what wavelengths 15 each radiation-sensitive semiconductor 22a, 22b and 22c respond. The control unit 19 divides the digital output signals into two categories, the first category comprising the digital output signals measured by radiation-sensitive semiconductors responding to wavelengths not at the absorption wavelengths of the gases investigated, and the second category comprising the digital output signals measured of radiation-sensitive semiconductors responding to wavelengths at the absorption wavelengths of the gases studied.

The control unit 19 comprises means for converting the digital output signals of the first category into digital temperature indicating signals. The controller 19 stores the first category of digital output signals in the RAM 21. The data regarding the digital temperature indicating signals from the first category and from which areas each digital temperature indicating signal from the first category is measured, is referred to in the following description as "second measured data ".

The data concerning the digital output signals from the second category and from which areas each digital output signal from the second category is measured are referred to in the following description as "first measured intensity".

DK 176996 B1 22

The control unit 19 comprises means for comparing the digital temperature indicating signals from the second measured data converted from the digital output signals measured by different radiation sensitive semiconductors at different wavelengths but in the same region. According to Planck's Radiation Act (I), the temperature must be the same. If the difference of the digital temperature indicating signals from the first category from the measurements in the same range is less than the first predefined difference value, the radiation is due to black body radiation and the measured temperature is judged to be the body temperature, hereinafter referred to as "first measured temperature". If the difference is greater than the first predefined difference value, the radiation is partially caused by radiation that is not from a black body or an error has occurred in the measurements or in the signal processing. The measurements from this area are not taken into account until measurements indicate radiation from a black body. A message or error message, warning or alarm can be triggered according to the 20 factual needs and circumstances.

The control unit 19 converts the first measured temperature to intensities according to Planck's radiation law (I) for each stored wavelength at which the gases studied absorb. These 25 intensities and corresponding wavelengths are hereinafter referred to as "first database intensities".

The control unit 19 comprises means for comparing the first measured intensities and the first database intensities, so that the radiation intensities at a wavelength from the first measured intensities are compared with the radiation intensities at the same wavelength from the first database intensities and their difference is calculated.

35 If the ratio is less than the third predefined value for the material, the situation is not interpreted as threatening and no action is taken. If the difference between the temperatures is not less than the third predefined value for the material, an alarm signal is sent. The alarm signal is sent via the electronic connection 25 to an alarm diode 26 5 which can be a light emitting diode. An alarm signal is also sent via bus 28 to an external gas alarm or to e.g.

ventilation system which will blow in fresh air or suck the gas out and may switch off the electricity and machinery located in the area if the gas is explosive.

10

FIG. 4 describes in more detail an example of the configuration of the fire detection system 16 shown in FIG. 3, with three radiation-sensitive semiconductors 35a, 35b and 35c. Electrical connections 36a, 36b and 36c forward the electrical 15 output signals from the radiation sensitive semiconductors to amplifiers 37a, 37b and 37c, respectively. The amplifiers have a negative feedback to avoid oscillations and temperature drift.

A circuit 38 with a zener diode 39 maintains the voltage which constantly supplies the amplifiers via electronic connection 40, 20 to provide stable amplification. Subcircuit 38 feeds a control unit 41 with a high and a low reference reference potential via electronic connections 42 and 43, respectively. Electronic connections 44a, 44b and 44c connect 3 amplifiers to low-pass filters 45a, 45b and 45c. Electrical connections 46a, 46b and 46c direct the output signals to the control unit 41. An external 8GHz oscillator 47, which acts as a clock for the control unit 41, is connected to the control unit. The power supply (not shown) feeds the control unit via electronic connection 48. A 30 switching function 49, used to switch the detector between the functions fire detector, gas detector and smoke detector, is connected to the control unit by four pins by means of electronic connections 50a, 50b, 50c and 50d. In one embodiment, the switching is done manually by means of a dipswitch.

35 DK 176996 B1 24

A programming interface 51 is used to enable communication between the controller and a computer. It consists of a JTAG port 52 which is connected to the control unit 41 via electronic connection 53a, 53b, 53c, 53d and 53e.

5

Claims (15)

25 DK 176996 B1 Requirements. A fire detection system (16) of the type comprising a first radiation-sensitive semiconductor (22a, 35a) for measuring a first radiation intensity at a first wavelength and emitted from a region susceptible to fire, forming a first output signal representing the first radiation intensity, and at least one second radiation-sensitive semiconductor (22b, 22c, 35b, 35c) to measure at least a second radiation intensity at at least a second wavelength and emitted from the region susceptible to fire and creating a second output signal representing it second radiation intensity, characterized in that the fire detection system (16) comprises, 15. the first radiation-sensitive semiconductor (22a, 35a) and the at least one second radiation-sensitive semiconductor (22b, 22c, 35b, 35c) are arranged in a predefined pattern, - that the fire detection system (16) has means for converting the first output signal to a first temperature indicating signal and the mind a second output signal for at least one second temperature indicating signal, - processor means for comparing the first temperature indicating signal with the at least second temperature indicating signal, which second temperature indicating signal serves as a control for the first temperature indicating signal, - a database (20) including ignition data for 30 materials on an easily flammable fire target, and - comparative means for comparing the temperature indicating signals with the database. Fire detection system (16) according to claim 1, characterized in that the pattern is selected from the group consisting of a 2-dimensional array, a 3-dimensional array, concentric circles, polygons or random order. Fire detection system (16) according to claim 1, characterized in that the radiation-sensitive semiconductors (22a, 22b, 22c, 35a, 35b, 35c) are selected from the group consisting of photodiodes, PIN diodes, CMOS circuits, bolometers or CCD chips and combination of these. Fire detection system (16) according to claim 1, characterized in that the radiation-sensitive semiconductors (22a, 22b, 22c, 35a, 35b, 35c) measure in the wavelength range from 200nm to 30μιη. Fire detection system (16) according to claim 1, characterized in that the means for converting an output signal to a temperature indicating signal, the processor means and the comparative means include a control unit (19, 41) and software programs. Fire detection system (16) according to any one of the preceding claims 1 to 5, characterized in that the fire detection system (16) further comprises at least one gas detector. Fire detection system (16) according to claim 6, characterized in that the database (20) comprises data representing the wavelengths at which at least some gases absorb radiation. Fire detection system (16) according to claim 6, characterized in that the fire detection system (16) has an external radiation source. Fire detection system (16) according to claim 6, characterized in that the fire detection system (16) comprises a spark detector 35 having a response time faster than 8ms and having a sensitivity lower than 1.1 mW / cm1. DK 176996 B1 27 Fire detection system (16) according to claim 6, characterized in that the fire detection system (16) comprises a smoke detector. Fire detection system (16) according to claim 6, characterized in that the fire detection system (16) comprises a temperature sensor. Method for detecting fire using the fire detection system (16) according to any one of the preceding claims 1 - 11, characterized in that the method comprises the steps of storing ignition temperatures of at least some in a database (20) on a control unit (19, 41). 15 materials located in an area susceptible to fire, - measuring radiation intensity from at least one area of the zone at a first specified wavelength with a first radiation-sensitive semiconductor (22a, 35a) returning a first output signal, - measuring radiation intensity from the least one area of the zone by at least one other specified wavelength with at least one other radiation-sensitive semiconductor (22b, 22c, 35b, 35c) returning at least 25 a second output signal, - converting the returned first output signal from the first radiation-sensitive semiconductor (22a , 35a) measured at the first wavelength of a first temperature indicating signal, 30. that ko invert the at least second output signal from at least one other radiation-sensitive semiconductor (22b, 22c, 35b, 35c) measured at at least one second wavelength to compare at least one temperature-indicating signal, 35. comparing the first temperature-indicating signal with at least one other temperature indicating DK 176996 B1 28 signal, and determining a first difference value, and if the first difference value is less than a first predefined difference value, then - comparing the first temperature indicating signal 5 with the ignition temperature of the database for the material in the monitored area and a second difference value is determined, and - if the second difference value is below another predefined difference value, an alarm signal is sent. 10 Process according to claim 12, characterized in that the first predefined difference value is chosen to be lower than 10 ° C. The method of detecting fire according to claim 12, characterized in that the method comprises the steps of storing absorption wavelengths for a large number of gas molecules in a database (20) on a control unit (19, 41), 20. measuring radiation intensity from at least one region in the zone at least one absorption wavelength for the at least one monitored gas molecule with a first radiation sensitive semiconductor (22a, 35a) returning an absorption output signal, 25. measuring radiation intensity from the at least one region of the zone at least one non-absorption wavelength for the at least one monitored gas molecule with at least one other radiation-sensitive semiconductor (22b, 22c, 35b, 35c) returning at least one non-absorption output signal, 30. comparing at least one absorption output signal with at least one non-absorption signal, and determining whether there is a difference between the at least one absorption output signal and the at least one non-absorption signal due absorption - and 9Q DK 176996 B1 2 y - to send an alarm signal if the difference is due to absorption. Method for detecting fire according to any one of the preceding claims 12, 13 or 14, characterized in that the method further comprises the steps of - converting the temperature corresponding to the first temperature indicating signal to an intensity for at least one absorption wavelength for at least one gas molecule to a first database intensity; - measuring the radiation intensity from the at least one region of the zone at least one absorption wavelength for the at least one monitored gas molecule with at least one radiation-sensitive semiconductor (22b, 22c, 35b, 35c), 15 returning at least one absorption output signal, comparing the at least one absorption output signal with the at least one first database intensity, and if the ratio of the absorption output signal to the first database intensity for the wavelength characteristic of the at least one gas molecule is less than a third predefined value, then - sending an alarm signal. 25