Cerberus Ag

Siemens Aktiengesellschaft

Siemens Schweiz Ag

Siemens Building Technologies Ag

Martin Forster

Aleksandar Duric

Mourad Baraket

Sigfrid Strassler

Harald Ebner

Claudia Illert

Rene Lenggenhager

Mauro Feltre

Rolf Pleisch

Georges Tenchio

Peter Nebiker

Andreas Portmann

A method for determining a triggering time for the issuance of an alarm by an alarm device. A measured value is sensed at a measuring time, and the measured value is indicative of a hazard potential within a monitoring range. A waiting time is identified by way of a function which respectively indicates an assigned waiting time for a plurality of different measured values and which has a continuous profile. The triggering time is determined on the basis of the measuring time and the identified waiting time. In addition, an alarm device having a detection device for sensing a measured value and having an evaluation device which is configured to carry out said method is described. In addition, a program element for determining a triggering time for the issuance of an alarm by an alarm device is described, wherein the program element can be loaded into an evaluation unit of the alarm device and can cause the abovementioned method to be carried out.

Determination of an alarm-issuing time of an alarm device

A method and test devices are used for field calibration of gas detectors. Brand new gas detectors are used as measurement standards in field calibration. The brand new gas detectors are in this case either employed directly as working standards, in which case the regular calibration by a reference standard is dispensed with, since the brand new gas detectors are always deemed to be sufficiently accurate. Alternatively, the brand new gas detectors are employed directly, namely as sufficiently accurately calibrated reference standards for the reference gas sensors acting as working standards and incorporated into the test device. In both cases the measured values of the gas sensors in the gas detectors to be calibrated are fed back to a sufficiently calibrated system, namely either directly to at least one brand new gas detector as a working standard or else to a reference sensor of a calibrated test device.

Method and test device for field calibration of a gas detector

A test device, for checking the functioning capability of a gas-alarm annunciator, has a reservoir in which are located a target fluid and a carrier fluid. At least a part of the carrier fluid is present in a liquid aggregate state and the target fluid is at least partially dissolved in the liquid carrier fluid. An extraction device engages into the reservoir such that the target fluid can be extracted along with the liquid carrier fluid. The target fluid is constituted such that on reaching a coverage area of a properly functioning gas-alarm annunciator it will cause the gas-alarm annunciator to annunciate an alarm. A test system and a test method for checking a gas-alarm annunciator's functioning capability use such a test device.

Function check for a gas-alarm annunciator

The measuring arrangement contains a measuring cell and a reference cell, respectively, and microphones assigned to these cells, to which microphones an electronic evaluation circuit is connected and in which a subtraction of the signals of the microphones takes place, as well as a radiation source for applying a modulated signal to the measuring cell. The modulation frequency of the radiation source coincides with the resonant frequency of the measuring cell, and the measuring cell and the reference cell are open at at least one end to the gas to and/or aerosol to be detected. The measuring arrangement is used as smoke alarm, gas alarm, fire hazard alarm or as combined smoke and gas alarm, wherein each of the measuring cells is exposed to a radiation of a wavelength at which a relevant substance to be detected is absorbent and an opto-acoustic effect is produced as a result.

Optoacoustic measuring arrangement and use thereof

In an optoacoustic gas sensor having a sensor body (1, 2), a light source (10), a measurement cell (6) with a gas-permeable membrane (15), a measurement microphone (13), and an optical measurement filter (11) between the light source (10) and the measurement cell (6), a reference cell (7) is included that is separate from the measurement cell (6). The reference cell (7) has a reference microphone (14) that is shielded against optoacoustic signals from the gas to be detected via the reference cell being substantially free from intensity-modulated optical radiation having an absorption wavelength of the gas to be detected. The measurement signal, which indicates gas concentration, is obtained by subtraction of the signals from the two microphones (13, 14).

Optoacoustic gas sensor

In a photo-acoustic gas sensor having a measuring cell, a lamp, a photo-diode, a gas-permeable diaphragm and a microphone, a device is included for monitoring the gas-permeable diaphragm and the microphone. The device is operated in an explosion-proof manner. Intentionally, for diagnostic purposes, an artificial pressure modulation is generated in the measuring cell. The pressure modulation is converted by the microphone into electrical monitoring signals which are amplified by an amplifier circuit and assigned to preset ranges by a microprocessor, for determining the functional condition of the diaphragm and the microphone, and of microphone sensitivity. Depending on the range assigned to the monitoring signal, an output signal is generated indicating a fault in the microphone and/or the diaphragm. In the event of long-term drift in microphone sensitivity, a calibration is performed in which gas concentration values are re-calculated and stored in an EEPROM. A heater wire can be used, for modulated heating to generate the pressure modulation.

Photo-acoustic gas sensor

A photo-acoustic gas sensor for measuring a gas concentration, e.g., of an explosive gas, consists of a cylindrical sensor body (1) which includes a cylindrical measurement chamber (13) whose longitudinal axis extends perpendicular to the longitudinal axis of the cylindrical sensor body. Without changing the outer dimensions of the sensor body, the length of the measurement chamber can be changed in accordance with a desired measurement sensitivity and a desired measurement range. A light source (5) is disposed such that it irradiates the measurement chamber without irradiating a gas-permeable membrane (2), so that the membrane will not produce an interference signal. The gas sensor is rendered explosion-proof as the light source and a photo-diode (6) which monitors the light source are tightly sealed from the environment. Proper functioning of a microphone (4), the light source and the photo-diode are monitored by analyzing a background signal.

Photo-acoustic gas sensor and its manufacture and use

A pyroelectric detector comprising a substrate, pyroelectric material distributed in a binder and applied to said substrate, and at least two electrically conductive electrodes, wherein the pyroelectric material comprises lithium tantalate consisting of single crystal particles, said lithium tantalate containing an amount of tantalum ranging from 25 to 75 mole % as tantalum pentoxide.

Novel pyroelectric detector

Reactive gases like, for example reducing gases, specifically carbon monoxide, are detected in a gas mixture, particularly in air, with extremely high sensitivity and with high precision using a gas detector in which the attenuation of the intensity of an infrared radiation beam by a catalyst layer is utilized. Such catalyst layer contains at least one transition metal selected from at least one of the groups I, VII, and VIII of the Periodic Table of the Chemical Elements. Preferably, chemical elements are used having an atomic weight in the range of about 100 to about 205. The detection of carbon monoxide is particularly sensitive using a catalyst layer which substantially contains a metal capable of forming a carboncarbonyl compound with carbon monoxide. The sensitivity and precisionof detecting carbon monoxide and other reducing gases can be significantly increased by periodically exchanging the gas mixture to be investigated in a measuring chamber and replacing it with a pure reference gas from a reference chamber. The sensitivity and precision of the gas detection can be further increased by periodically alternating the temperature of the catalyst layer during such period of gas exchange. The alternating signal this obtained at an output of the gas detector can be evaluated for determining the concentration of the reactive or reducing gases in the investigated gas mixture.

Method of detecting reative gases in a gas mixture

Reducing gases can be detected in a gas mixture to be investigated, particularly in air, with high sensitivity and precision by means of a gas detector. The gas detector comprises a gas sensor which is arranged within a measuring chamber. The temperature of the gas sensor can be continuously increased according to a predetermined pattern from a starting value to an upper threshold value and can be subsequently decreased again to the starting value according to the same or according to a different pattern. There are provided at least two such heating cycles. Simultaneously therewith the gas mixture to be investigated, which is present in the measuring chamber, is periodically exchanged against a pure reference gas which is contained in a reference chamber. A selected property, such as the electrical conductivity of the gas sensor is thereby periodically changed. The temporal variation of this periodically varying electric conductivity can be detected in an evaluation circuit arrangement and/or evaluated for determining the concentration and/or the nature of the reducing gases which are present in the gas mixture to be investigated.

Method of, and apparatus for, detecting reducing gases in a gas mixture

The device comprises a gas sensor containing a predetermined number of sensor elements which change their electric conductivity under the action of gases. Such a gas sensor is used for selectively determining the components of gas mixtures. For this purpose the individual sensor elements are arranged on a heat-resistant, thermally insulating substrate and the individual sensor elements are sensitized for the determination of different components of the gas mixture by selecting different materials and/or operating temperatures for the individual sensor elements. The sensor elements and its components are arranged such that the gas mixture to be investigated is guided past the sensor elments in a directed flow. The temperatures of the sensor elements increase in a stepwise manner in the direction of the gas flow and thereby a further increase in the selectivity of the gas sensor is achieved.

Device for selectively determining the components of gas mixtures by

Novel constituent materials for gas sensors detecting gaseous impurities in air contain metal oxides and catalyst additives. The materials are prepared by mixing a colloidal solution A of an oxide or a hydroxide of at least one metal selected from the groups Ib, IIa, IIb, IIIa, IIIb, IVa, IVb, Va, Vb, VIa, VIb, VIIb, VIII and the lanthanides and actinides of the periodic system with a solution B containing a salt or a complex compound of at least one metal selected from the group: lanthanum, chromium, manganese, iron, cobalt, nickel, copper, ruthenium, iridium, palladium, platinum, rhodium, osmium, silver, gold, antimony, bismuth, thorium, and irradiating the mixture thus obtained with light of the visible and ultraviolet spectral region in order to photochemically deposit the metal in finely distributed form on the metal oxide or metal hydroxide, respectively. The irradiated solution C thus obtained is processed without substantial change in the size of the colloidal particles of the metal oxide or metal hydroxide, respectively, in order to yield a solid D which subsequently is dried at a temperature which is higher than the intended operating temperature of the gas sensor by a maximum of 700.degree. C., particularly by a maximum of 500.degree. C. and preferably by a maximum of 300.degree. C.

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Jona, Switzerland

Martin Forster