Abstract: A thin film device having a selectively passivated surface is provided. An embodiment of the device is particularly suited to detection of chemical constituents by selective adsorption, where the selectively passivated surface is inert to the chemical constituent being detected. A method of fabrication of the device is also provided in which the selective passivation is achieved by selectively applying the metallic adhesive to the substrate. The migration of the metallic adhesive through the thin film layer is essentially normal to the surface of the substrate, thereby limiting the passivation of the thin film layer to the surface areas directly overlying the metallic adhesive.

Abstract: A surge absorbing structure capable of effectively utilizing the gaseous discharge is intended without a complicated structural configuration such as using the conventional discharge tube. To implement this, a porous layer 1 is formed by a non-conductive material to provide many holes, and sandwiched between a pair of electrodes 2a and 2b to allow the electrodes to be conducted by the gaseous discharge generated through the holes 3 in this porous layer to execute surge absorption.

Abstract: According to the present invention, a temperature sensor for high temperature comprises a ceramic plate on the surface of which is provided a thermistor layer, electrodes connected to the thermistor layer, and the thermistor layer containing ZnCr.sub.2 O.sub.4. It is preferable that the thermistor layer contain a resistance conditioning agent composed of either ZnO or Cr.sub.2 O.sub.3 or both, and that it contains at least one of the sintering auxiliaries selected from the group: SiO.sub.2, CaO, MgO, CaCO.sub.3, kaolin, and talc. Accordingly, it is possible to obtain stable resistance-temperature characteristics at high temperature as well as superior heat resistance.

Abstract: A combustible gas sensor comprises four glass insulated radially extended and symmetrical temperature sensitive elements which are coated with a porous ceramic but only two elements having a catalyst. The sensor is mounted inside a temperature controlled reactor vessel in a region of no temperature gradient into which a combustible gas mixture is admitted and reacted on the catalytic surfaces. The change in the resistance of the elements under the catalyst is a measure of the concentration of the combustible gas.

Abstract: Electrical resistors and resistor networks are provided on an insulative substrate with designated conductive terminations by direct and continuous writing of resistive lines in fine-line patterns between and over each two of neighboring terminations from heterogeneous resistive thick film compositions. The resistive lines of line width w and total length l between conductive terminations can be directly written by suitable writing apparatus to have a high aspect ratio n=l/w, thereby providing resistors and resistor networks of high resistance values on an overall substrate area significantly smaller than required for conventional thick film resistors of comparable resistance value and comparable operational characteristics.

Abstract: A microsensor system for determining water vapor content of the ambient atmosphere that uses a thin film suspended ceramic diaphragm structure featuring an embedded, patterned thin film heater, temperature sensor and an external film of an hygroscopic salt stabilized in a water-insoluble, crosslinked polymer matrix and contacting a pair of patterned electrodes which are proximate to the heater. The heater controls a selected electrical parameter of the salt to a fixed, predetermined value, as determined by its electrical characteristics. The dew point of the atmosphere is determined based on the dynamic relation with the salt dehydration temperature.

Abstract: A CO detector, utilizing periodical temperature change of a metal oxide semi-conductor gas sensor, is equipped with a backup battery. When power cut of a commercial power supply is detected, the detector will be driven by the battery, and the gas sensor will be heated at 50.degree.-100.degree. C. for from 30 seconds to 1 minute and will be kept at room temperature for about 30 minutes. CO is detected by the minimum sensor output after the heating.

Abstract: A measuring sensor for determining gas compositions, includes a substrate consisting essentially of Al.sub.2 O.sub.3, electrodes disposed on the substrate, a sensor layer consisting essentially of TiO.sub.2 disposed above the electrodes, and an adhesion-improving layer which consists essentially of Al.sub.2 TiO.sub.5 and which is disposed on the substrate, the adhesion-improving layer being at least partially connected with the electrodes. The adhesion-improving layer is provided to improve the adhesiveness of the electrodes, and includes a material in common with the material of the sensor layer, i.e., Ti. The material of the adhesion-improving layer is selected so as to prevent a chemical reaction between the materials of the substrate and the sensor layer.

Abstract: A method is disclosed for the protection of catalytic converters for exhaust gas purification by measuring the temperature with a heat tone sensor suitable particularly for the implementation of the method, wherein a heat tone sensor composed of at least two NTC or PTC resistors and provided with a coating of a catalytically active material on the sensor in the region of at least one of these resistors is arranged ahead of the catalytic converter in the exhaust gas stream or a part thereof, with the catalytically active material initiating the same exothermal reactions as they take place in the catalytic converter employed for the exhaust gas purification. If the resistor is overheated due to an overly intensive exothermal reaction, resulting in a change in resistance, the heat tone sensor detects the drop in the throughput rate of the catalytic converter.

Abstract: The invention includes a flat plate exhaust sensor including a flat plate sensing element which is carried by a first ceramic insulator having at its upper end an upwardly extending annular ring. The annular ring defines a disc-shaped recess which is filled with a glass seal. Thus, the glass seal extends from the flat plate sensor to the annular ring of the ceramic insulator. The sensor includes an upper tubular shell which includes at the lower end a leg portion which extends inside an inner wall of a lower tubular shell. The leg portion includes a foot which is bent to match an outwardly extending sloped annular shoulder formed on an upper insulator. The upper insulator is seated on the glass seal. An intermediate gasket is formed by an active metal braze gasket between the foot and the outwardly extending sloped annular shoulder of the upper insulator. An external seal is provided by a braze ring which joins an upper end of the lower tubular shell to the upper tubular shell.

Abstract: A thick film hydrogen sensor element includes an essentially inert, electrically-insulating substrate having deposited thereon a thick film metallization forming at least two resistors. The metallization is a sintered composition of Pd and a sinterable binder such as glass frit. An essentially inert, electrically insulating, hydrogen impermeable passivation layer covers at least one of the resistors.

Abstract: In an oxygen sensor of the type having an oxygen ion conductive tube of solid electrolyte, a ceramic heater disposed within the oxygen ion conductive tube for heating the same is in the form of a quadrangular prism or a bar of a rectangular cross section. The ceramic heater is formed by piling up ceramic green sheets with metallic thick-film patterns for heat generating resistors interposed between adjacent two of the ceramic green sheets. The ceramic heater is so shaped as to satisfy the relation of b/a=0.75.about.1 where "a" is the width and "b" is the thickness of the ceramic heater. The metallic thick films, which the metallic thick-film patterns are turned to by firing, are arranged so as to be parallel to the side surfaces opposed in the thickness direction of the ceramic heater.

Abstract: An ambient temperature solid state sensor for detecting the concentration of a gas includes an insulating substrate, a polycrystalline semiconducting oxide thin film deposited on the substrate such that the gas can be adsorbed on the surface of the film, the film having a low carrier concentration and a high resistivity, a pair of electrodes disposed on the film for measuring the electrical resistance of the film, and a source of light having a wavelength component which is absorbed by the thin film, thereby causing photodesorption of the gas from the surface of the film and establishing the equilibrium between gaseous species in the ambient and gaseous species adsorbed on the oxide surface. The resistance of the thin film is dependent on the amount of adsorbed gas, the measured resistance of the film thereby indicating the concentration of the gas.

Abstract: A gas sensor that has its heater and sensing layer on opposite sides of the substrate. The gas sensor includes a buffer layer separating the gas-sensing layer from the substrate to improve mechanical strength and electrical properties. The heater is preferably formed of nickel paste and is provided on the back of the substrate.

Abstract: An oxygen sensor is based on a thin film of a compound oxide supported on a substrate such as quartz. The compound oxide has a general formula ABO.sub.2.5+x, where A is an element of the lanthanum family, alkaline earth metal or their mixture, and B is a transition metal or a mixture of transition metals. X is a variable number, changing from about 0 to about 0.5 between the reversible oxygen-deplete and oxygen-rich forms of the oxide. In an elevated temperature and oxygen-containing atmosphere, the thin film can undergo reversible bulk oxidation resulting in a detectable change of its physical properties such as mass, optical transmissivity and electrical resistance.

Abstract: Sensors (10, 40) accurately measure the concentration of an oxide compound, such as nitrogen oxide NO.sub.x, in a gas mixture (11) which can include oxygen O.sub.2. The sensors (10, 40) each comprise a chamber (12, 42) adapted to receive the gas mixture (11) as well as first and second electrochemical cells (16, 17) for consuming oxygen and/or the oxide compound in the chamber (12, 42). The first electrochemical cell (16) comprises a first internal electrode (16a) inside the chamber (12, 42), a first external electrode (16b) outside the chamber (12, 42), and a first electrolyte body (14') therebetween. The second electrochemical cell (17) comprises a second internal electrode (17a) inside the chamber (12, 42), a second external electrode (17b) outside the chamber (12, 42), and a second electrolyte body (14") therebetween. The first and second electrolyte bodies (14', 14") are permeable to oxygen ions.

Abstract: A gas sensor having a large operation current and being operated at a relatively low temperature includes a substrate having a first surface and a second surface. A sensing area is provided on the first surface for increasing the conductivity across it when the sensing area detects a certain gas. A controlling area is provided on the first surface and beside the sensing area for permitting a tunneling current to pass therethrough when the sensing area cannot sense a certain gas or when the gas sensor is adapted to be sufficiently supplied with power. This control area prevents the tunneling current from being generated when the sensing area detects certain gas and thus the conductivity is increased, so that when the first and the second surfaces are electrically connected to the power supply. The gas sensor will be in an on state when the gas sensor cannot sense there is the certain gas and be in an off state when the gas sensor detects the presence of certain gas.

Abstract: This invention relates to solid-state smoke detectors and smoke (fire) alarm systems, and more particularly to a novel and improved smoke-sensitive element comprising a bismuth oxide film deposited on one surface of an electrically insulating material. It also relates to a method of depositing this oxide on a substrate, of heat treatment which provides for a highly smoke-sensitive film, and to smoke detector signal processing circuits.

Abstract: A solid-state, multi-stage gas detector for detecting a selected gaseous species from a plurality of gaseous species. The multi-stage gas detector includes a first conductive layer, exposable to the plurality of gaseous species, which permits the selected gaseous species to diffuse therethrough and which interacts with at least one of the plurality of gaseous species such that its conductivity changes. A second conductive layer, electrically isolated from the first conductive layer, interacts with the selected gaseous species after it has passed through the first conductive layer such that the second conductive layer's conductivity changes in relation thereto. Electrodes are attached to the first conductive layer and to the second conductive layer for separate detection of conductivity changes within the conductive layers. Detector conductivity changes comprise detection information correlated to the selected gaseous species.

Abstract: A hydrogen sensor element comprises an essentially inert, electrically-insulating substrate having a thin-film metallization deposited thereon which forms at least two resistors on the substrate. The metallization comprises a layer of Pd or a Pd alloy for sensing hydrogen and an underlying intermediate metal layer for providing enhanced adhesion of the metallization to the substrate. An essentially inert, electrically insulating, hydrogen impermeable passivation layer covers at least one of the resistors, and at least one of the resistors is left uncovered. The difference in electrical resistances of the covered resistor and the uncovered resistor is related to hydrogen concentration in a gas to which the sensor element is exposed.

Abstract: The invention relates to a sensor for the determination of carbon monoxide, especially in gas mixtures containing oxygen, on the basis of doped metal oxides whose electric conductivity is a function of the composition of the gas mixtures. Suitable metal oxides are those having n-type conductivity, the dopants used being other oxides of a metal having a maximum valency <4; oxides of a metal catalyzing the reaction of carbon monoxide with oxygen to give carbon dioxide, each in amounts from 0.01 to 0.2 mol %; and from 0.001 to 0.1 mol % of an oxide of a metal of the 5th subgroup of the Periodic Table of Elements. The sensors are notable for a small resistance-temperature coefficient while having high sensitivity and low hysteresis.

Abstract: Planar forms of chemically-sensitive materials have been combined, under temperature control, with the pixels of a specially-designed micro-hotplate array to produce a miniature device capable of analyzing chemical mixtures. The device uses integrated multiple elements having different adsorption properties and temperatures to collectively achieve chemical selectivity in sensing. The method of making and using selectively in sensing. The device of the present invention is manufactured by standard CMOS foundry techniques which allow the production of a range of devices that have improved sensing performance.

Abstract: A resistance probe is proposed for detecting gas compositions, particularly in the exhaust gases of internal combustion engines. This resistance probe has the advantage over prior art resistance probes that, with a short response time, it is considerably more aging resistant. This is accomplished in that the resistance layer configured as a semiconductor layer is introduced or sintered into recesses or slits provided for this purpose in the prefabricated sensor carrier body and above it is applied a porous, electrically non-conductive engobe or a protective layer structure in the form of a grid or raster. These measures enable the measuring gas to gain access to the semiconductor layer, but the semiconductor layer is simultaneously protected against corrosive, erosive and/or cavitative attacks from the exhaust gas.

Abstract: A contact combustion type carbon monoxide sensor having no sensitivity to H.sub.2, C.sub.2 H.sub.5 OH and other gases but having a CO sensitivity of 25 to 50 mV at a bridge voltage of 6 to 12 V and a concentration of 500 ppm. Each coil is made of a Fe.Pd system alloy wire material having a large diameter, a specific resistance value, a Vickers' hardness value and a temperature coefficient values each falling within a specific range. A catalyst comprising Cu.sub.2 O, ZnO, MnO.sub.2 and Pt black is formed on the upper surface of the coil of an active portion, and a catalyst comprising CuO and Cr.sub.2 O.sub.3 is formed on the upper surface of the coil of a dummy portion.

Abstract: A renewable gas sensor, renewable gas sensor base and a method for renewing a gas sensor. The renewable gas sensor has a substantially planar heater. A substantially planar separator is superimposed on the heater. The separator is electrically insulating and thermally conducting. An electrode array is superimposed on the separator. The electrode array and the separator define a plurality of juxtaposed sensing sites disposed in electrically conductive relation to the electrode array and in thermally conductive relation to the separator. A chemical sensing film is superimposed on the separator and said electrode array in one of the sensing sites.

Abstract: The present invention relates to a combined semiconductor gas sensor, this sensor is constituted by combining two portions, each of the portions is made of a different gas sensitive material, their resistance exhibit different variation with the variation of the density of a specific gas, a detecting signal is led out from the junction of the two portion. Because of the mutual compensation and propagation effect of the two portions of the above mentioned gas sensor, the stability and/or sensitivity as well as the stability to temperature and humidity and the initial relaxation time can be improved. Gas sensors of different characteristics can be obtained by different combinations of two different gas sensitive materials selected according to need.

Abstract: A gas component detecting element using particles of metal oxide. The particles are prepared and calcined, and then subjected to a treatment which enlarges a specific surface area thereof. Catalyst particles are supported on the surface of these particles, and then the particles are sintered. The gas component detecting element is formed from these particles. A detector formed in this way can be used for a long period of time without any change in characteristics.

Abstract: The invention concerns a process for manufacturing inert, catalytic or gas-sensitve ceramic layers for gas sensors which comprises coating an uncoated insulative substrate with a layer of paste composed of a powdered semiconductor material of SrTiO.sub.3 and an organic paste material having a thickness of 1 to 100 um and then subjecting the coated substrate to a three phase thermal treatment.

Abstract: A gas sensor includes a substrate, a heater member formed on the base member, a gas sensitive structure formed on the heater member by a process comprising the following steps of forming a stacked layer structure on the heater member, the stacked layer structure including at least a metal-oxide semiconductor layer and an insulating film, and carrying out a heat treatment with respect to the stacked layer structure so that a constituent of the insulating film is diffused in spaces among crystal particles of the metal-oxide semiconductor layer, and electrode layers are in contact with the gas sensitive structure.

Abstract: A highly sensitive and selective sensor for the detection of halogenated compounds comprises a bead of sodium lanthanum fluoride silicate, having the molecular formula NaLa.sub.4 (SiO.sub.4).sub.3 F, in which are embedded two noble metal electrodes, preferably a straight platinum wire near the center and a helical platinum wire near the periphery of the bead. A current passing through the helical wire maintains the sensor temperature at about 550.degree. C. by resistive heating. The electrical resistance between the two wires is deduced from measurements of the current passing through a fixed external resistor when a substantially constant voltage, preferably about 4 volts, is applied between the wires. A decrease in the measured resistance is an indication of the presence of a halogenated compound in the sample of air to which the bead is exposed. The sensor is preferably controlled by a microprocessor or microcomputer that also performs data processing.

Abstract: A gas sensor device has a carrier plate of ceramic or glass. The carrier has apertures which leave only strips in a spiral configuration connecting a middle region of the carrier to the outer region thereof. The apertures may be mere slits separating the connection strips or they may be apertures providing larger air gaps. On each middle region so provided on the carrier a sensor element is located that has two electrodes and a sensitive layer which establishes a conducting connection between the electrodes. The electrodes and the sensitive layer are directly applied to the upper surface of the middle region. The two electrodes are comb shaped and are placed in inter-digital configuration to define a meandering gap between them. On the underside of the middle region of the carrier a heating element for the sensor element is provided and, if desired, also a temperature measuring resistance for regulating the temperature produced by a heating resistor.

Abstract: Disclosed is a method for producing a gas component detecting element for detectors which comprises a sintered body of particles of a metal oxide wich changes in electrical resistance depending on relative atmosphere of combustible components in an exhaust gas, catalyst particles being supported on the surface of particles of the metal oxide, the method comprising the following steps:preparing particles of the metal oxide,calcining the particles of the metal oxide,subjecting the calcined particles to a treatment for enlarging specific surface area of the calcined particles,supporting catalyst particles on the surface of the particles subjected to the enlargement treatment, andsintering the particles which support the catalyst particles.The detector which has the above-mentioned gas component detecting element is also disclosed.

Abstract: Oxygen sensor for air-fuel ratio control is provided with a sensor element having an oxygen ion-conductive main body and electrodes on both sides thereof, and at least one porous protective layer covering the electrode on the exhaust gas side. The protective layer includes an oxygen storage component OSC without copresence of a noble metal catalyst. The protective layer is intermeshingly connected to the main body via spherical protrusions of the main body. Double-layered protective layer structure includes OSC noncontaining layer (optionally containing catalyst) and OSC containing layer, as inner and outer protective layer or vice versa. OSC containing layer is formed by impregnation with OSC-solution through immersing the respective porous protective layer, or by cosintering the OSC containing green coating layer. By impregnation 0.2 -8 wt %, or by cosintering 0.2-30 wt %, of OSC metal element is containable. The outer protective layer is thinner and more porous than the inner protective layer.

Abstract: A selective chemical species detector including a conductive polymer based sensing element having a detectable characteristic, for example, the polymer resistivity, permanently altered on exposure to a first chemical species and not permanently altered on exposure to a second chemical species. The detector then determines a permanent change in the detected characteristic and indicates the presence of a chemical species on detection of a such a permanent characteristic change. Also disclosed is a method of fabricating such a sensing element to achieve the desired selectivity.

Abstract: A selected component of a fluid mixture, for example a reduced sulfur compound vapor in air, is detected by selectively adsorbing the component onto a conductive thin layer of material having a chemical affinity for such component and observing the resultant change of electrical resistivity of the layer. The sensitivity of the detector changes with accumulation of the component on the sensor. The accumulation of the component on the sensor is removed by oxidizing and evolving the component from the sensor to restore the sensor to a linear operating region. The accumulated component is preferably oxidized by reacting the component with ozone. The dynamic range of the sensor is increased by counteracting the tendency for the component to accumulate by continuously feeding back ozone to or controlling the temperature of the sensor so that the sensor operates in a linear region near null.

Abstract: A humidity sensor composed of interdigitated electrodes and a material therebetween which is composed of Nafion wherein H+ cites have undergone ion exchange with at least one of NH4+ and Li+, Na+, Ag+ and Mg+.

Abstract: A selected component of a fluid mixture, for example a reduced sulfur compound vapor in air, is detected by selectively adsorbing the component onto a conductive thin layer of material having a chemical affinity for such component and observing the resultant change of electrical resistivity of the layer. The sensitivity of the detector changes with accumulation of the component on the sensor. The accumulation of the component on the sensor is removed by oxidizing and evolving the component from the sensor to restore the sensor to a linear operating region. The accumulated component is preferably oxidized by reacting the component with ozone. The dynamic range of the sensor is increased by counteracting the tendency for the component to accumulate by continuously feeding back ozone to or controlling the temperature of the sensor so that the sensor operates in a linear region near null.

Abstract: A thin film gas-sensitive device includes an insulating substrate having a pair of electrodes, a gas-sensitive layer having a gas sensitive substance deposited on the insulating substrate and electrodes, and a catalytic layer deposited on the gas-sensitive layer and insulating substrate as a non-continuous layer. The insulating substrate is partly uncovered because the electrodes, the gas-sensitive layer containing the gas-sensitive substance and the catalytic layer do not thoroughly cover the substrate.

Abstract: The sensor includes a sensing element of a copper oxide ceramic with perovskite related structures. Electrical circuitry responsive to the conductivity of the sensing element is provided. This conductivity is a function of the gas partial pressure. A preferred ceramic oxide is in the Y-Ba-Cu-O system and these compounds exhibit a markedly greater dependence of conductivity on oxygen partial pressure than materials previously used.

Abstract: An exhaust gas sensor containing BaSnO.sub.3 or the like and a process for producing the sensor. The BaSnO.sub.3 is made free of segregation and adapted to have acid-base strength of at least 6.8 as determined with Hammett's indicator. Causes to reduce the acid-base strength of the BaSnO.sub.3 includes presence of Si and B, and causes to increase the acid-base strength include addition of Mg or Ca. The desired BaSnO.sub.3 can be prepared by precipitating BaSnO.sub.3 hydrous crystals while preventing introduction of Si and B thereinto especially with use of a container lined with a synthetic resin to prevent introduction of Si and B from the container, adding Mg or Ca to the precipitate, and thermally decomposing the precipitate.

Abstract: Apparatus for detecting the level of ammonia in air comprises a conduit through which air is flowed as an airstream past two ammonia sensors that straddle an ammonia absorber. The apparatus also comprises a signal processing circuit for comparing signals generated by the two ammonia sensors with the difference representing the level of ammonia present in the air.

Abstract: A thermistor element composed substantially of a vanadium-containing titania having dissolved therein 0.01 to 10 at. %, based on titanium, of vanadium and optionally 10 at. % or less, based on titanium, of at least one element selected from the group containing of cobalt, copper, manganese, iron, nickel, bismuth, strontium, barium, lead and zinc. A gas sensor using the thermistor element as a temperature sensor is described.

Abstract: A smell sensing element and a smell sensing device utilizing the element. The smell sensing element has a semiconductor portion formed mainly of SnO.sub.2. The semiconductor portion has a first component of at least one selected from the group consisting of oxides of alkaline earth metals and a second component of at least one selected from the group consisting of oxides of Sc, Y, Ti, Zr, Hf, Th, Al, Ga and lanthanoids added thereto.

Abstract: An oxygen sensor has a planar sensor element which generates electromotive forces or varies an electric resistance between electrodes formed on opposite surfaces of the planar sensor element depending upon concentrations of oxygen in exhaust gases, a metallic housing member for housing the sensor element therein, a ceramic powder placed around the planar sensor element in the metallic housing member and adapted to fix the planar sensor element and form a gas-sealed section and ceramic supporters for compacting the ceramic powder under a given pressure therebetween. The portion of at least one of the ceramic supporters which contacts the ceramic powder is provided with a projection.

Abstract: An industrial process oxygen analyzer, and method of using same, incorporates an automotive oxygen sensor to minimize the criticalness of controlling heater temperature during operation. Higher sensor heater temperature, required to accommodate the automotive oxygen sensor, is achieved by application of higher supply voltage to the sensor heater. Current limiting of the heater supply circuit reduces stress on the sensor heater, even at the higher operating temperature.

Abstract: A moisture sensor (100) is provided that utilizes a sulfonated fluorocarbon film (10) having a thickness of less than about one micron and capable of providing accurate measurements of humidity and extremely fast response to change in humidity. A preferred embodiment of an electrical system (150) is disclosed for use with sensor (100) and a sulfonated tetrafluoroethylene perfluoroether copolymer form of the film is especially preferred.

Abstract: A gas detecting device includes a substrate and a plurality of gas sensitive elements supported by the substrate. A plurality of predetermined temperatures at which gases are detected are provided. The gas detecting device also includes a plurality of pairs of electrode leads supported by the substrate, each of the plurality of pairs of electrodes being connected to a corresponding one of the gas sensitive elements, and heater leads that are supported by the substrate and heat the plurality of gas sensitive elements so that each of the gas sensitive elements is set at a corresponding one of the plurality of predetermined temperatures.

Abstract: This invention provides a composition comprising a mixture or a fired product of a material of the general formula Sr.sub.(1+x)/2 La.sub.(1-x)/2 Co.sub.1-x Me.sub.x O.sub.3-.delta. (wherein Me: at least one of Fe, Mn, Cr and V; O.ltoreq.x.ltoreq.1; .delta.: loss of oxygen) and SrMeO.sub.3 (wherein Me: at least one of Ti, Zr and and Hf), and a catalyst and a multi-functional sensor using such composition. With this composition it is possible to improve the catalytic performance for cleaning exhaust gas grom combusters or internal combustion engines and to improve sensitivity or response characteristics of the sensors for detecting stoichiometric composition.

Abstract: A selected component of a fluid mixture, for example a reduced sulfur compound vapor in air, is detected by selectively adsorbing the component onto a conductive thin layer of material having a chemical affinity for such component and observing the resultant change of electrical resistivity of the layer. The sensitivity of the detector changes with accumulation of the component on the sensor. The accumulation of the component on the sensor is removed by oxidizing and evolving the component from the sensor to restore the sensor to a linear operating region. The accumulated component is preferably oxidized by reacting the component with ozone. The dynamic range of the sensor is increased by counteracting the tendency for the component to accumulate by continuously feeding back ozone to or controlling the temperature of the sensor so that the sensor operates in a linear region near null.

Abstract: A laminar gas-sensitive thick film consisting of ceramic semiconductor and metallic catalyzer is formed across a pair of electrodes carried by a ceramic substrate, and the nature of metallic catalyzer on an outer surface layer of the thick film is different from that of metallic catalyzer in that portion of the thick film which is in the proximity of the electrodes.