WO2009135524A1

WO2009135524A1 - Danger alarm

Info

Publication number: WO2009135524A1
Application number: PCT/EP2008/055553
Authority: WO
Inventors: Thomas Goulet; Ulrich Hoefer; Isabelle Vinage
Original assignee: Siemens Aktiengesellschaft
Priority date: 2008-05-06
Filing date: 2008-05-06
Publication date: 2009-11-12
Also published as: EP2281286A1

Abstract

A danger alarm (114) is described comprising a gas-sensitive semiconductor sensor device (115), an optical smoke detection device (118) and an evaluation unit (119). The evaluation unit is adapted to carry out an evaluation of a first output signal of the gas-sensitive semiconductor sensor device (115) and of a second output signal of the optical smoke detection device (118). The gas-sensitive semiconductor sensor device (115) can comprise a metal oxide semiconductor gas sensor and/or a gas-sensitive field effect transistor. Further provided is a method for recognizing a danger situation using the danger alarm (114) described above. The evaluation can optionally comprise a combining and/or comparing of the two output signals. Furthermore, the evaluation can be carried out relative to a temporal progression of the two output signals.

Description

description

alarm Devices

The invention relates to the technical field of danger detection technology. The invention particularly relates to a hazard detector having a gas-sensitive sensor device. The invention further relates to a method for detecting a dangerous situation using such a danger detector.

Automatic fire detectors can detect fire or its formation based on the physical characteristics of the fire and subsequently trigger an alarm. This can be used to initialize firefighting measures and warnings to people inside a building. By alerting competent security personnel and / or the fire brigade, measures can be taken to protect property and personal safety. Thus, the risk of the spread of a fire can be significantly reduced. An effective and reliable operation of the automatic fire detection systems is of great importance for use in homes, public facilities, transportation or industrial facilities. This is especially true for buildings that are difficult to evacuate, such as buildings with high ceilings

Hazard potentials such as hotels, single-family homes with many children, nursing homes, etc.

Known fire detectors are characterized by the detector or sensor principles used and their mode of action. For example, fire gas or flue gas detectors, heat detectors, smoke detectors, flame detectors and so-called multicriteria detectors are used for fire detection.

A fire gas or flue gas alarm triggers an alarm when the concentration of carbon monoxide, carbon dioxide or other combustion gases in a room reaches a certain level Value exceeds. Fire gas or smoke detectors typically use a gas sensor.

A heat detector triggers an alarm when the room temperature exceeds a certain value, such as about 60 ° C, or within a certain time the ambient temperature rises above average.

Smoke detectors use various physical effects to detect smoke. In optical scattered light detectors, for example, light scattering of smoke particles is used for fire smoke detection.

A flame detector uses characteristic emissions of a flame in a specific spectrum (infrared to ultraviolet) to detect a flame.

A so-called multi-criteria detector combines in a device e.g. an optical smoke detector and a heat detector. By evaluating several output signals, multi-criteria detectors can be made less sensitive to false alarms.

However, the above-mentioned detectors are only suitable for a simple classic detection of the fire or its emergence. You can not provide any further information regarding the fire or the development of the fire.

The invention is based on the object, a hazard detector and a method for detecting a dangerous situation under

To specify use of this hazard alarm, which allow increased significance for a danger message.

This object is achieved by the subject matter of the independent patent claims. Advantageous embodiments of the present invention are described in the dependent claims. Independent claim 1 describes a danger detector with a gas-sensitive semiconductor sensor device, an optical smoke detection device and an evaluation unit for evaluating a first output signal of the gas-sensitive semiconductor sensor device and a second output signal of the optical smoke detection device.

The above-mentioned danger detector is based on the knowledge that the functionality of a classic fire alarm can be extended by combining two different sensory principles in an advantageous manner. In principle, it is possible to combine the sensory principles used for a classic fire alarm in a variety of ways. An optimized choice of these principles may be of considerable importance in terms of effective and reliable operation of such a hazard detector. Criteria and constraints, such as low power consumption, sufficient sensitivity and cross-sensitivity, distinctness of a plurality of different signals, and economics, may be considered in the selection of the sensory principles to be combined.

In the above-mentioned danger detector, a detection system of an optical smoke detector (smoke detection device) is advantageously combined with a detection system of a gas-sensitive semiconductor sensor (gas-sensitive semiconductor sensor device). An evaluation unit can evaluate both an output signal of the optical smoke detector and an output signal of the gas-sensitive semiconductor gas sensor. However, the evaluation unit will preferably carry out an evaluation based on both output signals.

The evaluation unit may, for example, an analog-to-digital converter for converting and a multiplexer for combining identify the two output signals. Furthermore, the evaluation unit can identify a processor which is suitable for evaluating the two output signals individually or in a combination by means of a corresponding software. The evaluation unit can either be used together with the gas-sensitive

Semiconductor sensor device and the optical Rauchdetektion- be on a chip monolithically integrated or built hybrid.

This makes it possible, in addition to the classic detection of Branden, to make statements about other dangerous situations such as the presence or use of hazardous substances. Examples of hazardous substances are hazardous gases and / or liquids, in particular fire-hazardous, fire-fighting substances, fire-accelerating substances, explosive gas mixtures and / or explosive dust.

Fire-hazardous substances can be substances that are particularly suitable for causing a fire hazard. For example, they may be flammable, highly flammable, highly flammable and self-ignitable substances. Fire-accelerating substances can be understood to mean flammable chemical substances used to increase the rate of fire propagation. Examples of accelerating substances are liquids such as ethanol, gasoline or the like, which can be poured over objects to be burned.

Substances that support combustion but are not flammable can be considered as fire-fighting substances. Examples of fire-fighting substances are oxygen, oxygen-rich salts such as potassium chlorate, peroxides and fluorine.

If, for example, the presence of hazardous substances in a room is detected early by means of the danger detector, then the dangerous substance can be eliminated. Also can be warned in time before the occurrence of explosive gas mixtures. If, for example, a timely warning is no longer possible in the case of an arson, it is also possible to create a possibility of recognizing the potentially used fire-fighting substance and of initializing monitoring devices. Thus, for example, records of surveillance cameras can facilitate law enforcement.

Furthermore, statements about causes of fire such as, for example, arson, leakage of fire-fighting substances, plant defects can also be made with such a danger detector.

The combination of the detection systems of the optical smoke detector and the gas-sensitive semiconductor sensor also makes it possible to detect explosive dust and / or its fire products. In principle, dust can also be detected with an optical smoke detector. But if these are only so present in their nature or concentration that they can not be recognized as a typical fire smoke, then usually no alarm is triggered. If there is subsequently an ignition of the dust, the fire can be detected by means of the gas-sensitive semiconductor sensor and / or the optical smoke detector. An evaluation of the time course of the output signals then makes it possible to detect the dust as the cause of the fire.

The evaluation unit can compare and / or superimpose the output signals of the gas-sensitive semiconductor sensor and the optical smoke detector and / or relate the time profile of the output signals to one another in order to be able to estimate the cause of the fire. In this case, a combined evaluation of the output signals both before a fire as well as during a fire can be performed. Thus, for example, another cause of fire or an additional latent fire hazard can be detected. Information on possible causes of fire, together with information on dangerous situations, should be used against the background of a suitable choice of extinguishing agents, clarification of property protection issues, identification of causes such as arson, discharge of fire-fighting substances, plant defects, prosecution of an arsonist and warning and evacuation of persons very desirable.

With the mentioned danger detector it becomes possible to realize a comprehensive extension of the safety concept in living rooms, public buildings, means of transport or industrial plants. Among other things, it may be possible to detect natural gas, which can form an explosive gas mixture with the air and is a fire-demanding substance. Also, it becomes possible to detect toxic gases such as carbon monoxide (CO), which may be released by defective incinerators.

Thus, a single device - the hazard detector - can trigger various types of alarms, such as a "fire" alarm, a "fire-demanding" alarm, a "CO" alarm, a "dust" alarm. Furthermore, relevant information regarding a determination of the cause of the fire and a recommendation for extinguishing agent can be determined. Also, control and control mechanisms of, for example, surveillance cameras and / or emergency exits can be activated.

According to an exemplary embodiment of the invention, the gas-sensitive semiconductor sensor device has a metal oxide semiconductor gas sensor.

The use of metal oxide semiconductor gas sensors for hazard detectors may be advantageous as they are inexpensive, have high sensitivity, simple electronic circuitry, and a lifetime of up to several years. sen. A metal oxide semiconductor gas sensor changes its electrical conductivity or resistance as soon as certain gases act on it. Typical gases that can be detected with metal-oxide-semiconductor gas sensors are, for example, propane, butane, methane, natural gas, carbon monoxide, sulfur dioxide, nitrogen monoxide and / or nitrogen dioxide. Metal oxide semiconductor gas sensors can also be used to detect ammonia, alcohol, etc. The metal oxide semiconductor gas sensor may be a gas-sensitive metal oxide semiconductor material layer such as tin dioxide

(SnO ₂ ), Zmkoxid (ZnO), titanium dioxide (TiO ₂ ), tungsten oxide (WO ₃ ), vanadium pentoxide (V ₂ Os), gallium oxide (Ga ₂ O ₃ ) or chromium titanium oxide (Cr ₂ _ _x Ti _x 0 _{3 + z} ) exhibit. Different materials can be used to achieve selectivity to specific gases. For a proof of carbon monoxide and / or nitrogen monoxide and / or methane tin dioxide can be used, for a proof of nitrogen dioxide can tungsten oxide and for a proof of ammonia Cr ₂ _ _x Ti _x 0 _{3 + z} . There may be lower limits of detection, for example, about 5 ppm for carbon monoxide, about 20 ppm for nitrogen monoxide, about 10 ppb for nitrogen dioxide, about 200 ppm for methane, and about 5 ppm for ammonia.

The acceptor density at the surface of the metal oxide which determines the electrical conductivity is influenced by a gas reaction with the gas to be detected. Thus, the conductivity or the resistance of the metal oxide semiconductor gas sensor can be changed. During operation, a sequence of this gas reaction could be triggered and / or accelerated by heating the metal oxide semiconductor gas sensor and the selectivity required. Depending on the materials used and the gases to be detected, temperatures between 150 ⁰ C and 900 ⁰ C, for example 150 ° C, 300 ⁰ C, 500 ° C, 700 ° C or even 900 ⁰ C are used. Depending on

The nature of the gases reacts differently with the metal oxide surface. The intensity of the Effect is also dependent on the selected temperature of the metal oxide. For example, the sensitivity of a Ga ₂ O metal oxide sensor to carbon monoxide (CO) decreases to higher operating temperatures. That is, the relative conductivity change decreases with increasing temperature. For methane (CH ₄ ) z. B. remains the sensitivity of Ga ₂ 0 ₃ obtained -Metalloxidsensors substantially with increasing temperature. By using a method of operation which operates the metal oxide semiconductor gas sensor, for example cyclically at different temperatures, gases can be distinguished from one another using suitable evaluation methods in this way. In addition, with metal oxide semiconductor gas sensors, which can be heated and cooled down again correspondingly, since they have a low thermal mass, temporal aspects of the gas reaction can be included in the evaluation. Here, the property of the gases is based on being able to have different adsorption and desorption times; ie the residence time of the gases on the semiconductor surface may depend on the type of gas. These differences can be found in the temporal form of the sensor signal and can thus be included in the evaluation. A lower working temperature, on the other hand, can additionally provide for low power consumption. Depending on the embodiment, the metal oxide semiconductor gas sensor may have a heating and cooling time of less than 100 ms. Ideally, the above-mentioned gas reaction is completely reversible and, in combination with a thermal cycling process, enables detection and discrimination of a variety of gases.

By means of the metal oxide semiconductor gas sensors, intelligent control and evaluation methods can be used which can be suitable for reliably detecting fire situations. By means of the above-mentioned intelligent control and evaluation methods, fire types and relevant gases can be distinguished from each other and different danger situations can be identified. According to a further exemplary embodiment of the invention, the gas-sensitive semiconductor sensor device has an arrangement of a plurality of metal oxide semiconductor gas sensors.

With the arrangement of metal oxide semiconductor gas sensors, the number of gases to be detected can be considerably increased. Thus, a fire and / or a fire hazard can be detected earlier. Also, thus a cause of fire can be determined more effectively and completely. Each individual metal oxide semiconductor gas sensor of the array of multiple metal oxide semiconductor gas sensors can react differently to a particular event. This results at any time in a signal pattern, which is composed of the individual output signals. These signal patterns and / or corresponding

Signatures can subsequently be compared with entries stored in an event library and assigned to the entries, if necessary. Each additional single metal oxide semiconductor gas sensor increases the detection reliability of an event. By the multiplicity of from an arrangement of

Information derived from metal oxide semiconductor gas sensors does not require complete selectivity of the individual sensors to individual gases.

According to a further exemplary embodiment of the invention, the metal oxide semiconductor gas sensor or the arrangement of a plurality of metal oxide semiconductor gas sensors has a carrier element with a thickness of less than 100 μm, preferably less than 50 μm and in particular less than 1 μm.

The support element may be formed as a thin membrane. Preferably, the metal oxide semiconductor gas sensor is micromechanically manufactured with such a support element. An extremely thin cross section for a solid state warming line can result in very good thermal isolation of the metal oxide semiconductor material layer from remaining portions of the metal oxide semiconductor gas sensor. This can be a very low heating power requirements result to maintain a constant temperature. For example, only a few 10 mW are required in such metal oxide semiconductor gas sensors in order to stably maintain the metal oxide semiconductor material layer at a temperature of 400.degree. Further, the good thermal insulation, in conjunction with a flat configuration of the remaining parts of the metal oxide semiconductor gas sensor on the support member, has allowed an extremely small time constant for the heating and cooling of individual components of the metal oxide semiconductor gas sensor, such as the support member and the Metal oxide semiconductor material layer, lead. The carrier element can be made for example of silicon nitride Si 3 N _4th

In the case of an arrangement of a plurality of metal oxide semiconductor gas sensors, it may be constructed on a single support member. In this case, different gas-sensitive metal oxides and / or a differently treated metal oxide can be used, wherein the treatment of the metal oxide z. B. may have a doping or addition of a catalyst.

Examples of how individual metal oxide semiconductor gas sensors are controlled in a temperature-pulsed manner and evaluated by a pattern recognition method in order to distinguish gases from one another by means of a single micromechanically produced metal-oxide semiconductor gas sensor are described, inter alia, in:

A. Schütze, A. Gram, T. Ruhl: Identification of Organic

Solvents by a Virtual Multisensor System with Hierarchical Classification, In: IEEE Sensors J, vol. 4, pp. 857-863, December 2004.

T. Kunt et al: Optimization of temperature-controlled sensing for gas identification using micro-hotplate sensors, Sensors & Actuators B53 (1998), 24-43. RE Cavicchi, JS Suehle, KG Kreider, M. Gaitan and P. Chaparala: Fast Temperature Programmed Sensing for Micro-Hotplate Gas Sensors, IEEE Electron Device Letters, 16, (1995), 286-288.

According to a further exemplary embodiment of the invention, the gas-sensitive semiconductor sensor device has a gas-sensitive field-effect transistor.

The use of the gas-sensitive field-effect transistors may be advantageous since they (a) may have very small dimensions (for example approximately 2 mm ² ), (b) can measure both in the heated state and at room temperatures, (c) have a long service life and (d) have a minimum power consumption. The gas-sensitive field effect transistors for a measurement of leaks and an explosion warning can thus be used particularly advantageously. Furthermore, the gas-sensitive field effect transistors are characterized by a simple signal readout. The gas sensitive field effect transistors are also inexpensive and can be used in high numbers for production of gas sensors of various types.

A gas sensitive field effect transistor can be constructed as a modified CMOS FET. Gas detection may be based on a change in workfunction at a gate. Between the gate and a transistor channel, a small air gap is established, which is open to a gas space. Thus, a gas can be detected by the change in the work function on the gate, which is equipped with a gas-sensitive gate layer.

The gate provided with gas-sensitive layers can be constructed in a micromechanical manner in a whole wafer. For example, a measurement range may begin at approximately 100 ppm. The low power consumption makes it possible to combine the gas sensitive field effect transistors with metal oxide semiconductor gas sensors.

According to a further exemplary embodiment of the invention, the gas-sensitive semiconductor sensor device has an arrangement of a plurality of gas-sensitive field-effect transistors.

An important advantage of the gas-sensitive field-effect transistors is that they can be constructed by means of a hybrid construction, wherein a common base unit can be used by different gate coatings for different gases. Thus, entire arrangements of gas-sensitive field-effect transistors can be realized inexpensively and in the smallest space and thus form a plurality of different gas sensors. Each individual gas sensor of the arrangement of gas-sensitive field-effect transistors can react differently to a specific event. This results at any time in a signal pattern, which is composed of the individual output signals. These signal patterns and / or corresponding signatures can subsequently be compared with the entry of a stored event library and assigned to this entry if necessary. Each additional individual sensor increases the detection reliability of an event. Due to the large number of information originating from an arrangement of gas-sensitive field-effect transistors, a complete selectivity of the individual sensors to individual gases is not necessary. With the arrangement of gas-sensitive field effect transistors, the number of gases to be detected can thus be increased considerably. Thus, a fire and / or a fire hazard can be detected earlier.

Also, thus a cause of fire can be determined more effectively and completely. Since the individual gas-sensitive field-effect transistors have a low power consumption, the total power consumption of the arrangement can also be kept low. Similar to the metal oxide semiconductor gas sensors, the field effect transistors and arrangements of field effect transistors may also be particularly well suited to exploit intelligent control and evaluation methods, to reliably detect fire situations, to distinguish fire types and relevant gases from each other, and to be able to identify different hazardous situations.

An example of an analysis of gas mixtures, the principle of which is easily transferable to the arrangements of field-effect transistors mentioned here, is described in:

U. Hoefer, A Felske, G. Sulz and K. Steiner: SnO ₂ -

Multi-Sensor Systems for the Analysis of Gas and Odor Mixtures, Proceedings GMA Conference "Process Automation in the Food Industry", 1-2 February 1996.

According to a further exemplary embodiment of the invention, the gas-sensitive semiconductor sensor device is set up for the detection of a hazardous substance.

The detection of hazardous substances can be very important in terms of early detection of a hazardous situation.

If the presence of hazardous substances in a room is detected early, the hazardous substance can be eliminated. It is also possible to warn in good time about the occurrence of potentially explosive gas mixtures. If, for example, a timely warning is no longer possible in the case of an arson, it is also possible to create a possibility of recognizing the potentially fire-resistant substance used and subsequently initializing monitoring devices.

According to a further exemplary embodiment of the invention, the gas-sensitive semiconductor sensor device has a heating element.

As a rule, a metal oxide semiconductor gas sensor has an integrated heating element. However, it is conceivable that the metal oxide semiconductor gas sensor can also be heated externally. The field effect transistors are usually operated either unheated or continuously heated to moderate temperatures around 100 ° C. However, a field effect transistor can also be equipped with a heating element, so that the field effect transistors or arrangements of field effect transistors can also be operated at different temperatures with the aid of this heating element. This can increase the selectivity or detection sensitivity of individual sensors, as in the case of metal oxide semiconductor gas sensors, and thus increase the detection reliability of an event.

The heating element may be constructed, for example, as a platinum heater or a polysilicon structure. Furthermore, the gas-sensitive semiconductor sensor device can also have a temperature sensor. An output signal of the temperature sensor can advantageously be used to have another measurement signal available for the detection of a dangerous situation.

According to a further exemplary embodiment of the invention, the average power consumption of the gas-sensitive semiconductor sensor device during operation is less than 10 mW, preferably less than 5 mW and in particular less than 1 mW.

In order to meet the requirements of the corresponding standards of a fire alarm system, the danger detector described preferably has a power consumption in the range of only a few mW. A particularly low power consumption can be achieved with the mentioned hazard detectors, which are based on gas-sensitive semiconductor sensor devices. In order to ensure the low power consumption, especially with metal oxide semiconductor gas sensors based on hazard detectors, modern, effective temperature modulation technologies can be used. This can result in a very low heating power requirement. Thus, For example, in such metal oxide semiconductor gas sensors only a few 10 mW needed to keep the metal oxide semiconductor material layer stable at a temperature of 400 ° C. Further, the good thermal insulation, in conjunction with a flat configuration of the metal oxide semiconductor gas sensor on the support member, could result in an extremely small time constant for the heating and cooling of the support member, metal oxide semiconductor material layer and heating element.

According to a further exemplary embodiment of the invention, the optical smoke detection device has a scattered light detector and / or a linear smoke detector.

A use of a scattered light detector or a linear

Smoke detector allows reliable detection of smoke and / or dust. The scattered light detectors and linear smoke detectors have a low power consumption. Thus, the total power consumption of the danger detector can be kept low and remain in the range of a few mW.

Scattered light detectors can operate according to a scattered light method based on the so-called Tyndall effect. It uses the knowledge that clear air reflects or scatters virtually no light. But are smoke and / or dust particles in the air and thus in an optical chamber of the scattered light detector, a Pruf light beam, for example, an infrared light emitting diode (LED) is scattered on the smoke and / or dust particles. A portion of the resulting scattered light can then be detected by a light receiver such as a photodiode.

Scattered light detectors are well suited, for example, for the early detection of Schwelbranden with relatively large and bright smoke particles. Thus, scattered light detectors can preferably be applied when, for example, in a Fire breakout with cold smoke is expected. In order to increase the sensitivity of the scattered light detector, instead of a simple LED, a very bright laser diode can be used.

A linear smoke detector responds to a smoke-induced attenuation of an infrared light beam emitted by a transmitting unit and received by a receiving unit. The linear smoke detectors may be well suited, for example, for monitoring large areas.

According to a further aspect of the invention, a method for detecting a dangerous situation using the inventive hazard alarm is specified.

With such a method, the above-mentioned advantages of the danger detector could be optimally utilized. A suitable method, which advantageously takes into account the two sensory principles combined by the hazard detector, may allow a single hazard detector to be used, for example, for effective and reliable detection of fires, fires, hazardous gases, fire-fighting substances, explosive gas mixtures and dusting can.

According to a further exemplary embodiment of the invention, the evaluation has a combination and / or a comparison of the first output signal and the second output signal.

By combining and / or comparing the two output signals, it becomes possible to determine information concerning a dangerous situation, a fire and / or a cause of the fire, which go beyond information about the individual output signals. Thus, for example, another cause of fire or an additional latent fire hazard can be detected. According to a further exemplary embodiment of the invention, the evaluation is carried out with respect to a time profile of the two output signals. In this case, the evaluation unit can compare and / or superimpose the output signals of the gas-sensitive semiconductor sensor and the optical smoke detector and / or relate the time profile of the output signals to one another in order to be able to estimate the cause of the fire. Such an evaluation of the output signals can be carried out both before a fire and during a fire.

According to a further exemplary embodiment of the invention, an evaluation process is initiated in the evaluation unit by the exceeding of a predetermined threshold value of an output signal of the gas-sensitive semiconductor sensor device (115) and / or the optical smoke detection device (118).

With the evaluation process, which is triggered by the exceeding of the threshold value, it can be achieved, for example, that the evaluation process is carried out only at certain concentrations of certain gases and / or only at certain concentrations of smoke and / or dust particles. In this case, the evaluation process can be triggered, for example, if the concentration exceeds a certain value or within a certain time, the concentration increases above average quickly. The appropriate thresholds may be selected for a preferred application and / or functionality of the hazard alarm. For example, false alarms and / or unnecessary evaluation processes can thus be avoided. The evaluation process can thus be triggered by means of a suitable trigger.

According to a further exemplary embodiment of the invention, a heating element of the gas-sensitive semiconductor sensor device operated so variable in time that at least temporarily a change in the temperature of the gas sensor element occurs and the time course of the change in temperature is used as the heat measurement signal.

In this context, a warm measurement signal can be understood to mean a thermal recovery signal which is largely produced by an energy input from the gas reactions. In this case, an exothermic oxidation of the gases to be detected on the gas-sensitive semiconductor sensor device, the time course of the temperature change in response to a change in heating turn out differently than when the gases are not present or in a different concentration. The shape of this time course can thus also be used as a large measure of these gases.

Alternatively, the heat measurement signal can also represent a heat conduction signal, which is generated predominantly by the heat conduction of gases. In this case, a gas composition around the gas-sensitive semiconductor sensor device influences its thermal conductivity. If the gas-sensitive semiconductor sensor device is warmer than the surrounding gas, its cooling by the heat conduction of the gas will depend on the gas composition. This can be read off on the heating course or on the course of cooling of the gas-sensitive semiconductor sensor device.

The time course of the change in temperature, ie the transient heat measurement signal, can be evaluated in various ways. Thus, for example, a temporal change in temperature can be considered directly after switching off the heating, ie the slope of the temperature-time behavior. Another possibility is to look at the change in temperature after a predetermined time has elapsed. Another possibility is to determine the time that elapses for a predetermined change in temperature. According to a further exemplary embodiment of the invention, the gas-sensitive semiconductor sensor device is heated in first time sections such that it at least reaches a temperature threshold, and in second time periods the gas-sensitive semiconductor sensor device is operated less heated or unheated than in the first time sections. The duration and sequence of the first and second time periods as well as the second temperature is selected such that the average power consumption incurred by the operation of the heating element is less than an upper heating power limit, with 10 mW, preferably 5 mW, and 10 mW as the upper heating power limit in particular 1 mW is used.

The first and second sections can alternate and as a temperature threshold, for example 150 ° C can be used. At least one respective output signal of the gas-sensitive semiconductor sensor device from the second time segments can be taken into account. Alternatively, a course of a plurality of output signals of the gas-sensitive semiconductor sensor device can be taken into account in each case from the second time sections.

It is also possible to use further time segments in which the gas-sensitive semiconductor sensor device is heated in such a way that it assumes further temperatures after a leveling of its temperature, the other temperatures also being selected such that the average power consumption resulting from the operation of the heating element, is smaller than the upper heating power limit. The length of the first time periods can be less than 1 s and the length of the second time periods can be more than 10 s, whereby the sequence and duration of the time periods can be adjusted during operation. In this case, the heating element can be operated within at least part of the time segments with a constant heating voltage or constant heating power set for each of these periods. Further advantages and features of the present invention will become apparent from the following exemplary description of presently preferred embodiments.

FIG. 1 shows a danger detector.

FIG. 2 shows a metal oxide semiconductor gas sensor.

FIG. 3 shows a gas-sensitive field-effect transistor.

FIG. 4 shows an arrangement of a plurality of gas sensitive field effect transistors.

FIG. 5 shows an evaluation of output signals of a metal oxide semiconductor gas sensor and an optical smoke detection device.

FIG. 6 shows an evaluation of output signals of a

Arrangement of a plurality of gas-sensitive field-effect transistors and an optical smoke detection device.

It should be noted at this point that in the drawing the reference symbols of identical or corresponding components differ only in their first digit and / or by an appended letter.

FIG. 1 shows a schematic representation of the structure of a danger detector 114. The danger detector 114 has a basic element 117. A micromechanically produced metal oxide semiconductor gas sensor 115, an optical smoke detection device 118 and an electronic circuit with an evaluation unit 119, a multiplexer 116 and a heating supply unit 120 are constructed on the base element 117. The multiplexer 116 is connected to the metal oxide Semiconductor gas sensor 115, the optical smoke detection device 118, the heating supply unit 120 and the evaluation unit 119 and connected to a not shown heating element of the metal oxide semiconductor gas sensor 115.

The multiplexer 116 ensures that the output signals of the metal oxide semiconductor gas sensor 115 and the output signals of the optical smoke detection device 118 can be combined and / or compared in an evaluation process. Furthermore, the multiplexer 116 ensures that the heating supply unit 120 is connected to the heating element of the micromechanically produced metal oxide semiconductor gas sensor 115 in the first time segments, and thus the metal oxide semiconductor gas sensor 115 is heated. Furthermore, in the second time periods, the heating element of the micromechanically produced metal oxide semiconductor gas sensor 115 can be connected to the evaluation unit 119 either by means of the multiplexer 116 or directly. This eliminates the heating of the metal oxide semiconductor gas sensor 115 and a measurement of the ambient temperature by the evaluation unit 119 is made possible. Alternatively, the heating supply unit 120 can also be connected directly both to the heating element of the metal-oxide-semiconductor gas sensor 115 and to the evaluation unit 119. As a result, if appropriate, a control loop can be formed between the heating supply unit 120, the metal-oxide-semiconductor gas sensor 115 and the evaluation unit 119.

Alternatively or additionally, in the danger detector 114, a gas-sensitive field effect transistor (GasFET), which will be described below with reference to Figure 3, are used. The GasFET can also be operated unheated.

FIG. 2 shows the cross section of a micromechanically produced metal oxide semiconductor gas sensor 215. The micromechanically produced metal oxide semiconductor gas sensor 215 has a carrier element 222, for example of silicon nitrite Si3N ₄ on. The support element 222 is usually square or rectangular and lies on a frame of silicon

221, which can be produced by means of an anisotropic etching process from a silicon wafer. The carrier element 222 has a heating element 224. This is in the example given as Maander resistor made of platinum. The ground resistor 224 becomes in a region of the carrier element

222, which is located on the frame of silicon 221, contacted from the outside. The heating element 224 is covered by an insulating layer 223, which may, for example, comprise silicon dioxide (SiC> ₂ ). On the insulating layer 223 finally sits a gas-sensitive metal oxide semiconductor material layer 225, which may have, for example, doped with palladium tin dioxide. The metal oxide semiconductor material layer 225 is usually contacted via metallic terminals, which are not shown in FIG.

The carrier element of the micromechanically produced metal oxide semiconductor gas sensor 215 is only about 1 μm thick in these examples. This extremely thin cross section for the solid state warming line results in extremely good thermal insulation of heating element 224 and the gas sensitive metal oxide semiconductor material layer 225 from the remainder of the structure. This results in a very low heating power requirement to maintain a constant temperature. Thus, only a few mW 10 are needed to maintain the gas-sensitive metal oxide semiconductor material layer 225 stably at a temperature of, for example, 400 ⁰ C, for example at such a micromachined metal oxide semiconductor gas sensors.

Furthermore, the good thermal insulation in interaction with the relatively flat structures on the support element 222, which are not shown to scale in FIG. 2, leads to a very low thermal mass of the element to be heated

Construction. This in turn leads to an extremely small time constant for the heating and cooling of the carrier element. ment 222, the heating element 224 and the gas-sensitive metal oxide semiconductor material layer 225. The micromechanically produced metal oxide semiconductor gas sensor 215 can thus reach a temperature of, for example, about 225 ° C. within less than 150 ms in the heated state. In the unheated state, ie after a switch-off time, the micromechanically produced metal oxide semiconductor gas sensor 215 can reach the ambient temperature even faster, namely in less than 100 ms.

FIG. 3 shows a gas-sensitive field-effect transistor 315, which will also be referred to below as the gasFET for short. The GasFET 315 is based on a field effect design. GasFET 315 includes a drain 335, a source 334, and a catalytic gate having a gas sensitive gate coating 336 to which gas molecules 339 can adsorb. Furthermore, the gasFET 315 has a temperature sensor 333. The temperature measured by the temperature sensor 333 is taken into account in the evaluation of the signal of the GasFET 315 in order to compensate for influences of the ambient temperature on the signal of the GasFET 315. This can be important if the GasFET 315 is not heated and is thus delivered directly to the ambient temperature. In a danger detector 114, the signal of the temperature sensor 333 can now be advantageously used in order to have available a further measurement signal for the detection of a dangerous situation.

4 schematically shows an arrangement of a plurality of gas-sensitive field-effect transistors 415. According to the exemplary embodiment described here, various semiconductor materials such as barium titanate doped copper oxide (BaTiO ₃ / CuO) 436A, palladium-doped tin dioxide (Pa / SnO ₂ ) 436B, Copper phthalocyanine (CuPC) 436C and polyamide (PA) 436D are used as gas sensitive gate coatings. Thus, by means of a CMOS transformer 437, this order may include a CO ₂ sensor 415A, a CO sensor 415B, a Have Nθ ₂ sensor 415C and a humidity sensor 415D. The arrangement of a plurality of gas-sensitive field effect transistors may alternatively replace the metal oxide semiconductor gas sensor 115 in the hazard alarm 114 or be used in addition to this. Similarly, an arrangement of a plurality of gas sensitive metal oxide semiconductor gas sensors may alternatively replace the metal oxide semiconductor gas sensor 115 in the hazard alarm 114 or be used in addition thereto.

Figure 5 shows a flow of an evaluation of output signals of a metal oxide semiconductor gas sensor and an optical smoke detection device. The gas-sensitive metal oxide semiconductor gas sensor is preferably operated by temperature pulses and different temperature ramps with a suitable temperature pulse method 551. In this case, the gas-sensitive metal oxide semiconductor gas sensor is heated accordingly, for example, suitable current or voltage pulses are applied to the heating element 224 shown in FIG. 2 by the heating supply unit 120 of the gas-sensitive metal oxide semiconductor gas sensor 115 shown in FIG. Depending on the selected temperature pulses and temperature ramps, the gas reactions at the gas-sensitive metal oxide semiconductor material layer will proceed differently, so that the metal oxide semiconductor gas sensor supplies a characteristic of the detected gas molecules output signal. This can be evaluated by means of a subsequent pattern recognition method 552A.

By using mathematical algorithms, signatures of different gases are recognized, as for example in the publication A. Schütze, A. Gramm, T. Ruhl: Identification of Organic Solvents by a Virtual Multisensor System with Hierarchical Classification, In: IEEE Sensors J, vol. 4, pp. 857-863, December 2004.

Signatures can be understood, for example, to be gas-characteristic reaction curves which show, for example, the resistance and / or the impedance of the metal oxide semiconductor gas sensor. Furthermore, the term signatures can be understood to mean the corresponding rise curves of the resistance and / or the impedance of the metal-oxide-semiconductor gas sensor. The measured signatures can be compared with signatures stored in a database. Thus, for example, the evaluation may provide information as to whether a fire-demanding substance is present. Furthermore, as a result, if necessary, also the type of the existing fire-fighting substance can be determined. Furthermore, as a result, a concentration of one or more hazardous gases such as CO may be reported. Also, the information as to whether a combustion gas is present and possibly also its concentration can be provided. In addition, as a result, the information about the time profile of the output signal and / or the concentrations of the gases to be detected can be given.

In parallel, an evaluation of the output signal of the control light detector or the linear smoke detector is performed. This output signal can also be evaluated by means of a pattern recognition method 552B. Using mathematical algorithms, signatures of smoke and dust are detected. The signatures can in the case of the control light detector, the time course of the intensity and / or the Flackerfrequenz and / or the Signalabnahmebzw. Increase rate of scattered light have. In the case of the linear smoke detector, the signatures may include the time course of the intensity and / or the flicker frequency and / or the rate of decrease or decrease of the transmitted light received by the receiving unit. These signatures can be compared to signatures stored in a database. Thus, as a result, the evaluation may, for example, provide the information as to whether smoke and / or dust is present. Furthermore, as a result, the type and concentration of the smoke and / or dust particles can be reported. Also, as a result, the information about the temporal Course of the output signal and / or the concentrations of smoke and / or dust particles are supplied.

Subsequently, the two output signals of the metal oxide semiconductor gas sensor and the optical smoke detection device are superimposed and compared 553. Also, the evaluation of the superposition and the comparison can be carried out similarly as described above by means of a pattern recognition method. Furthermore, this evaluation may include an analysis of the time profile 553 of the output signals. Through the combined evaluation 553 of the two output signals described here, additional statements can be made, such as whether it burns without smoke, whether a fire was assisted and / or triggered by a fire-fighting substance. Optionally, an identification of the burning medium can be made. In addition, measures and / or recommendations regarding the type of a suitable extinguishing agent and / or a control of various actuators, such as, for example, the start of a surveillance camera and / or an activation of emergency exits, can be output with this information.

The evaluation process by the evaluation unit can be triggered, for example, by exceeding a threshold value of the gas-sensitive semiconductor sensor device and / or the optical smoke detection device.

FIG. 6 shows a sequence of an evaluation of output signals of an arrangement of a plurality of gas-sensitive field effect transistors and an optical smoke detection device. The evaluation 652A, 652B, 653 is carried out analogously to the evaluation described in relation to FIG. Here, output signals from different sensors 415A, 415B, 415C and 415D are available for the arrangement of a plurality of gas sensitive field effect transistors shown in FIG. The evaluation of the output signals of the arrangement of a plurality of gas-sensitive field-effect transistors can be carried out in various ways. An evaluation method currently considered particularly suitable is described in the publication by U. Hoefer, A Felske, G. Sulz and K.

Steiner: SnC> ₂ multi-sensor systems for the analysis of gases and odors, conference proceedings GMA conference "Process automation in the food industry", 1-2 February 1996.

In the evaluation, statistical methods such as

Example principal component analysis, multivariate data analysis and / or linear discriminant analysis are applied.

The sensory principles described in this application particularly emphasize the low power consumption, the low price, the high sensitivity to different gases and the stability of the sensors used. The advantages mentioned represent an important prerequisite in order to realize the danger alarms described in this application and to enable their operation in electronic networks and bus systems.

It should be noted that the embodiments described herein represent only a limited selection of possible embodiments of the invention. Thus, it is possible to combine the features of individual embodiments in a suitable manner with one another, so that a multiplicity of different embodiments are to be regarded as obviously disclosed to the person skilled in the art with the embodiments explicitly illustrated here.

Claims

Patent claims

1. Danger detector (114) with

• a gas-sensitive semiconductor sensor device (115), • an optical smoke detection device (118) and

• an evaluation unit (119) for evaluation

a first output signal of the gas-sensitive semiconductor sensor device (115) and

- A second output signal of the optical smoke detection device (118).

2. A hazard detector (114) according to claim 1, wherein the gas-sensitive semiconductor sensor device (115) comprises a metal oxide semiconductor gas sensor (215).

3. hazard detector (114) according to any one of the preceding claims, wherein the gas-sensitive semiconductor sensor device comprises an arrangement of a plurality of metal oxide semiconductor gas sensors (215).

4. A hazard detector (114) according to claim 2 or 3, wherein the metal oxide semiconductor gas sensor (215) or the arrangement of a plurality of metal oxide semiconductor gas sensors, a support member (222) having a thickness of less than 100 .mu.m, preferably less than 50 .mu.m and in particular less than 1 micron.

5. hazard detector (114) according to any one of the preceding claims, wherein the gas-sensitive semiconductor sensor device comprises a gas-sensitive field effect transistor (315).

6. hazard detector (114) according to one of the preceding claims, wherein the gas-sensitive semiconductor sensor device comprises an arrangement of a plurality of gas-sensitive field effect transistors (415).

7. Danger detector (114) according to one of the preceding claims, wherein the gas-sensitive semiconductor sensor device (115) is adapted for the detection of a hazardous substance.

8. hazard detector (114) according to one of the preceding claims, wherein the gas-sensitive semiconductor sensor device (115) has a heating element (224).

9. A hazard detector (114) according to any one of the preceding claims, wherein the average power consumption of the gas-sensitive semiconductor sensor device (115) in operation is less than 10 mW, preferably less than 5 mW and in particular less than 1 mW.

10. hazard detector (114) according to any one of the preceding claims, wherein, the optical smoke detection means (118) comprises a scattered light detector and / or a linear smoke detector.

11. A method of detecting a hazard situation using a hazard alarm (114) according to any one of the preceding claims.

12. The method of claim 11, wherein the evaluation comprises combining and / or comparing the first output signal and the second output signal.

13. The method according to any one of claims 11 or 12, wherein the evaluation is carried out with respect to a time course of the two output signals.

14. The method according to any one of claims 11 to 13, wherein in the evaluation unit (119) an evaluation process by the exceeding of a predetermined threshold value of an output signal of the gas-sensitive semiconductor sensor device (115) and / or the optical smoke detection device (118) is triggered.

15. The method according to any one of claims 11 to 14, wherein a heating element (224) of the gas-sensitive semiconductor sensor device (115) is operated variable in time so that at least temporarily a change in the temperature of the gas-sensitive semiconductor sensor device (115) occurs, and the time course of the change the temperature is used as a heat measurement signal.

16. The method of any of claims 11 to 13, wherein in first time periods, the gas-sensitive semiconductor sensor device (115) is heated so that it reaches a temperature threshold at least, and in second time periods, the gas-sensitive semiconductor sensor device (115) schwa- heated rather than in the first time periods or unheated, wherein the duration and sequence of the first and second time periods and the second temperature is selected so that the average power consumption incurred by the operation of the heating element is less than an upper heating power limit, with 10 mW as the upper heating power limit, preferably 5 mW and in particular 1 mW is used.