Abstract: In order to determine a concentration of a gas mixture, especially a hydrogen concentration of a containment atmosphere of a nuclear power station, a temperature change resulting from a catalytic reaction is measured. The gas mixture is diluted with a motive gas of known composition. The dilution is carried out by a jet pump.

Abstract: A sensor housing (10) for directing the flow of a gas over two sensitive regions (53, 54) of sensing device (52) includes an inner shroud (12) surrounding the sensing device (52). The inner shroud (12) is inserted into an outer shroud (14), such that a plurality of gas channels (44) are formed between the inner shroud (12) and the outer shroud (14). In operation, a gas enters through inlet orifices (28) in the outer shroud (14) and travels through the gas channels (44) to the proximal end (26) of the inner shroud (12). The flow direction of the gas is then reversed and the gas passes through an inner chamber (50) and over sensitive regions (53), (54) located on the surface of the sensing device (52). Vacuum pressure created at an outlet hole (46) located at a distal end (35) of the outer shroud (14) draws the gas out of the inner chamber (50) and return the gas to the exterior of the sensor housing (10).

Abstract: A means for detecting carbon monoxide which utilizes an un-heated catalytic material to oxidize carbon monoxide at ambient temperatures. Because this reaction is exothermic, a thermistor in contact with the catalytic material is used as a sensing element to detect the heat evolved as carbon monoxide is oxidized to carbon dioxide at the catalyst surface, without any heaters or external heating elements for the ambient air or catalytic element material. Upon comparison to a reference thermistor, relative increases in the temperature of the sensing thermistor correspond positively with an increased concentration of carbon monoxide in the ambient medium and are thus used as an indicator of the presence of carbon monoxide.

Abstract: A catalytic detector for a flammable gas comprises a substrate and a sensing structure suspended from the substrate. The sensing structure has a combined heating element and temperature sensing element in the form of a layer-deposited electrically conductive track terminating in at least two electrically conductive bridging leads. A catalytic bead is deposited over the temperature sensing element and that portion of the substrate which is directly beneath the sensing structure is etched away so as to isolate thermally the sensing structure with the temperature sensing structure being supported by the bridging leads. The electrically conductive track is sandwiched between a substrate adhesion layer for facilitating adhesion of the conductive track and a superstrate diffusion barrier layer. The invention extends to a method of manufacturing a gas detector and a sensing structure.

Abstract: A device for sensing ammonia (NH.sub.3) and nitrogen oxide (NO.sub.x) gases comprising: a sensor for detecting said ammonia and said nitrogen oxide gases, said sensor including a substrate and a layer consisting of cuprate material for detection of said ammonia and said nitrogen oxide gases, wherein said layer of cuprate material is selected from the group consisting of Y:Ba:Cu:O (YBCO) and Bi:Sr:Ca:Cu:O (BSCCO); a sensor holder for supporting said sensor; a perforated cap positioned over said sensor, said perforated cap having openings for passage of said ammonia and said nitrogen oxide gases to said sensor; a detection circuit communicating with said sensor for measuring output from said sensor; and a display or recording device connected to said detection circuit for displaying or recording a concentration of said ammonia and said nitrogen oxide gases based on the output from said sensor.

Abstract: A substrate carrying a first electrode and a second electrode, the first and second electrodes being disposed adjacent to one another, the first electrode being disposed between the substrate and a gas-sensitive component, the gas sensitive component comprising an n-type semiconductor, the gas-sensitive component having a resistance that is gas-dependent and temperature-dependent, and the second electrode being disposed between the substrate and a non-gas-sensitive component, the non-gas-sensitive component comprising a n-type semiconductor and a p-type semiconductor, the non-gas-sensitive component having a resistance that is temperature-dependent and that is not gas-dependent and wherein the n-type semiconductor of the non-gas-sensitive component is Ga.sub.2 O.sub.3 and the p-type semiconductor of the non-gas-sensitive component is ZrO.sub.2.

Abstract: In a gas sensor for sensing reducing or oxidizing gases which comprises a semiconductive metal oxide film, there are provided stripe-like outer electrodes which define therebetween a continuous surface area and stripe-like inner electrodes which extend between, and parallel to, the outer electrodes so as to divide the continuous surface area into longitudinal segments which have different properties with respect to reducing or oxidizing gases such that different conductivity changes are generated for the different segments upon exposure to oxidizing or reducing gases.

Abstract: A gas sensor for detecting the presence of gases in air. In particular, sensors are described that have a compound catalytic support structure and are suitable for sensing hydrocarbons and nitrogen oxides. The device features a ceramic substrate having a temperature sensitive resistor on one surface. A mixture of ceramic particles and glass powder are applied over the substrate and resistor and fired so that the glass flows and adheres the ceramic particles to the substrate. A catalyst layer of either platinum or rhodium is deposited on the catalyst support and a thermally sensitive resistor element detects reactions of hydrocarbons or nitrogen oxides on the corresponding catalyst. The invention is suitable for sensing gases in the harsh environment of an automobile exhaust system.

Abstract: A transition metal oxide based calorimetric non-methane hydrocarbon sensor (100) is constructed by disposing a transition metal based catalyst (105), preferably chromium oxide (Cr.sub.2 O.sub.3), onto a carrier (101). A temperature measurement device (103) is positioned thermally coupled to the transition metal based catalyst (105). A preferred application includes sensing non-methane heavy hydrocarbons in an automotive exhaust gas stream (803) by exposing a transition metal oxide catalyst based sensor (805) to the exhaust gas stream (803) and providing a signal (811) indicative of a concentration of non-methane heavy hydrocarbons and carbon monoxide (CO). Then, exposing a compensating sensor (807) to the same exhaust gas stream (803) and providing a compensating signal (813) indicative of a concentration of carbon monoxide (CO). By combining the signal (811) and the compensating signal (813), a measure of non-methane heavy hydrocarbons can be provided.

Abstract: There is disclosed an automated apparatus and process for immunocytochemical staining of biological materials using ligand pairing. The apparatus includes an array of sample cells interconnected with reagent supply and drainage lines. Each cell encloses a fluid chamber into which a sample substrate is inserted. The face of the substrate onto which a biological sample is mounted faces into a fluid well. The cell includes a cell head having a chamber to receive therein a solid support matrix releasably containing a ligand to be contacted with the sample. The chamber in the cell head is in flow communication with the fluid well so that when the ligand is released from the matrix it flows into the fluid well thereby contacting the mounted biological sample. The ligand support matrix may be gelatin or wax.

Abstract: A sensor for hydrogen is disclosed comprising an electrically insulating substrate carrying a thin amorphous film of co-deposited nickel and zirconium and an overlying film of palladium wherein during the operation of the sensor, hydrogen in a sample gas is dissociated on the palladium film and diffuses into the nickel-zirconium film to change its electrical resistance in proportion to the amount of hydrogen in the sample to be analyzed.

Abstract: The invention relates to a combination of a heated lambda sensor with a stepped or binary sensor characteristic and another heated lambda sensor to determine the lambda value in a gas mixture, e.g. in the exhaust gas preferably of internal combustion engines, the output signal from one lambda sensor being used to calibrate the other one, and the two lambda sensors are arranged closely beside each other, the other lambda sensor having a wide-baud sensor characteristic.

Abstract: A sensor including a micro-bridge heater which is located above a depression in the surface of a substrate. The heater includes a first insulating film on the substrate, a conductive film on the first insulating film, and a second insulating film on the conductive film. The first and second insulating films are made of the same material, preferably tantalum oxide (Ta.sub.2 O.sub.5) and are the same thickness. A foundation film is not employed as an adhesive between the first insulating film and the conductive film due to the strong adherence between the first insulating film and the conductive film which is preferably made of platinum or a platinum alloy. Because the first and second insulating films are made of the same material and have the same thicknesses, the insulating films have similar rates of thermal expansion and the expansion or contraction of the insulating films offset each other, thus reducing the thermal stress imposed on the conductive film.

Abstract: A thin-film gas sensor and manufacturing method of the same is disclosed which includes a silicon substrate; an insulating layer formed on the surface of the silicon substrate; a heater formed in zigzag on the surface of said insulating layer; a temperature sensor formed in zigzag on the surface of the insulating layer in parallel with the heater; an interlayer insulating layer for electrically insulating the heater and temperature sensor formed on the insulating layer; a plurality of electrodes formed on the interlayer insulating layer placed between the heater and temperature sensor; a plurality of pairs of gas sensing layers disposed in an array on the electrodes and for reacting on detected gas; and a plurality of gas shielding layers formed on one gas sensing layer out of the pair of gas sensing layers and for shielding the detected gas so that the gas sensing layers do not react on the detected gas.

Abstract: For an exhaust analyzer, the factors causing turbulence and mixing of the sample gas are removed from the sample gas-introducing pipe in order to introduce the sample gas into the analyzer cell under laminar conditions. Further, the indicated changes resulting from the fluctuations of sample gas pressure within the analysis cell of such a construction are compensated. As a result, the sample gas can be quantitatively analyzed with a high rate of response under the condition that the influences caused by the fluctuations of the sample gas pressure are reduced.The sample gas is introduced into the cell-type gas analyzer from the sample gas source through a gas-introducing pipe under laminar conditions.

Abstract: A matched catalytically inactive compensator for use in a combustible gas sensor is made from a catalytically active detector. The catalytically active detector is exposed to a gas phase catalytic inhibitor such as hexamethyldisiloxane to completely destroy its catalytic ability thereby forming a compensator which has very similar chemical and physical properties to the untreated detectors.

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 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 dual-column, dual-detector gas detector and analyzer employs both a photo-ionization detector and a flame-ionization detector. In a survey mode, samples of ambient air are driven through both detectors, and the outputs of both detectors are used to determine the presence of one or more gasses. In analysis mode, fixed-volume samples of ambient air are driven through two elution columns having different properties. The output of each elution column is fed to one of the detectors. The arrival times of gas peaks at the two detectors are employed to develop two lists of candidate gasses. The lists are cross-checked for the presence of each candidate on both lists. Candidates identified from their presence on both lists are identified. A further check attempts to identify candidates which are identifiable from their presence on one of the lists, and not on the other. Components identified in this way are added to the final list.

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 catalytic combustion type CO gas sensor which is composed of an electrical circuit by serially arranging two coils composing an active section and a compensating section, and by providing serial bridge resistances, r.sub.1 and r.sub.2, opposing to the said coils, respectively, and via a gas sensitometer, and which determines the CO concentration based on the difference in value of resistance of both coils of the active section and the compensating section on catalytic combustion of CO, characterized by:(A) that the values of the resistance of coils of the active section and the compensating section and bridge resistances, r.sub.1 and r.sub.2, at a definite temperature are made substantially the same, and thus the temperature coefficients of the coil of the active section and the bridge resistance r.sub.1, and of the coil of the compensating section and the bridge resistance r.sub.2 are made approximately the same.(B) that the value of resistance of the coil of the active section at 150.degree.-200.degree.

Abstract: Several types of new microelectronic devices including diodes, transistors, sensors, surface energy storage elements, and light-emitting devices are disclosed. The properties of these devices can be controlled by molecular-level changes in electroactive polymer components. These polymer components are formed from electrochemically polymerizable material whose physical properties change in response to chemical changes, and can be used to bring about an electrical connection between two or more closely spaced microelectrodes. Examples of such materials include polypyrrole, polyaniline, and polythiophene, which respond to changes in redox potential. Each electrode can be individually addressed and characterized electrochemically by controlling the amount and chemical composition of the functionalizing polymer. Sensitivity of the devices may be increased by decreasing separations between electrodes as well as altering the chemical environment of the electrode-confined polymer.

Abstract: A sensor comprising a metal heat generating member formed with a heat-resistant insulating coating of Al.sub.2 O.sub.3 or the like over its surface, and an atmosphere-sensitive layer of SnO.sub.2 or the like supported on the coating. The insulating coating is formed, for example, by alumina sol coating and thermal decomposition, or plasma CVD of an aluminum compound. The sensitive layer is formed, for example, by the thermal decomposition of an organic compound of tin, vacuum evaporation or sputtering of tin, or printing of SnO.sub.2 on the heat generating member when the member is in the form of a flat plate. At least one electrode is connected to the sensitive layer for deriving an output from the layer in response to a combustible gas, humidity or the like.

Abstract: A method of selectively sensing the quantity of methane gas in an oxygen containing gas stream, which method, as taught in one of its preferred embodiment, includes the step of providing a platinum catalyst (12) and a palladium catalyst (14). The platinum and the palladium catalysts are electrically interconnected (16--16) so as to obtain an electrical output reading (24) therefrom. The electrically interconnected catalysts are heated to a temperature in a range of 350.degree.-450.degree. C. whereby a reference electrical output reading is obtained therefrom. A gas stream containing suspected methane is passed over the electrically interconnected catalysts. Methane gas contained in the gas stream is oxidized only by the palladium catalyst while all other oxidizable components of the gas stream are oxidized by both catalysts.

Abstract: Apparatus for detecting a combustible gas which comprises a Wheatstone bridge circuit having a detector element comprising an electrically conducting member coated with a refractory and having on the surface of said refractory a catalyst for the oxidation of said gas, said detector element constituting one leg of said bridge, and a reference element comprising an electrically conducting member coated with a refractory, said reference element constituting a second leg of said bridge, whereby upon catalytic oxidation of said gas an electrical signal approximately proportional to the amount of said gas present at the detector element is produced. The improvement comprises a reaction control block having a cover in the form of a dust shield and having two chambers, one containing said detector element, and the other containing said reference element.

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.

Abstract: A method detects the proportion of combustible gas in a mixture of air with a measuring device which operates by both the heat-tone and heat-conductivity methods. The method permits measurement in the full concentration range with a high degree of accuracy and the lowest possible energy consumption. The measuring device is made small and light and its sensor has a long service life. The method uses one single sensor which operates at a low temperature in the heat-conductivity mode or alternatively, catalytically active at a higher temperature in the heat-tone mode. If the measurement provides a result below a reference value or within a reference value window, measurement continues in the more accurate heat-tone mode. When the gas concentration increases during measurement, in order to avoid ambiguity of the measuring signal and damage to the sensor above a load-limit value, measurement again takes place in the heat-conductivity mode by reducing the temperature of the sensor.

Abstract: A method of detecting oil aerosol in an air flow. The contaminated air is passed between an electrode (11) and an electrically conductive catalyst (14), and an electrical discharge therebetween causes electrostatic precipitation of oil on to the catalyst. Air flow and discharge are stopped, and the catalyst is heated with the air substantially stagnant until the catalytic combustion temperature of the oil is reached. The heat generation due to such combustion is sensed and used to produce an output signal indicative of the quantity of deposited oil.

Abstract: A combustible gas sensor element prepared by the process of applying, to a sheathed wire coil, separate coats of catalytic wash each heated in a furnace, separate and alternating coats of porous ceramic and platinum each heated by passing an electric current through the coiled wire filament, and separate coats of porous ceramic top coating, each heated by passing an electric current through the filament.

Abstract: Impurity compensation for compensating the analysis of the calorific content for fuel having an unknown amount of a known additional constituent of interest (impurity) is disclosed. In the illustrative embodiment oxygen is the impurity. In that embodiment, the fuel containing the impurity is combusted to achieve substantially stoichiometric combustion by varying the air/fuel ratio supplied to a combustion means by a rotary speed controlled in response to the sensing of oxygen in the combustion products. A first measurement of the calorific content is made using a normal operation of the analyzer and a second measurement is made using a known amount of air added to the combustible gas stream. The true air/fuel ratio and the calorific content is then computed using a predetermined relationship among the system variables.

Abstract: A combustible gas sensor element prepared by the process of applying, to a sheathed wire coil, separate costs of catalytic wash each heated in a furnace, separate and alternating coats of porous ceramic and platinum each heated by passing an electric current through the coiled wire filament, and separate coats of porous ceramic top coating, each heated by passing an electric current through the filament.

Abstract: A gas sensor element for detecting the presence of a flammable gas comprises an electrical resistance filament surrounded by a bead which is formed by an array of alumina particles interspersed between and bound together only by particles of a catalyst to form an open porous gas diffusive skeletal matrix having a mean particle size of less than 20 nm. When the bead includes such a matrix, the number of active sites at which catalytic oxidation of flammable gases can take place is greatly increased with the result that the sensor element is very resistant to poisoning by atmospheric contaminants such as traces of silicone and sulphur compounds. The sensor thus has a very much longer life and does not require such frequent recalibration.

Abstract: An element for detecting combustible gases comprises a catalyst material associated with an electrical resistor serving as both a heater and a thermal sensor, the catalyst material being produced by heating a deposit from an aqueous slurry of alumina, of maximum particle size 0.1 micron, containing in solution a compound of a metal of the platinum group. The deposited material may constitute a pellet (6) within which is embedded a coiled part (3) of a wire (1) constituting the resistor. The element then resembles a conventional "pellistor" in form, but has improved resistance to poisoning or inhibition of the catalyst.

Abstract: A reference element for a catalytic gas sensor with improved life in the presence of combustible gases is described. The sensor comprises a filament such as a platinum-iridium alloy coated with a layer of titanium dioxide. The coating typically contains a high temperature stable inorganic binder such as aluminum oxide. The filament can be in coil-form pre-encased in a glass bead. Such sensor has long term stability in the presence of combustible organic gases such as alkenes, alkadienes, alkynes, and epoxide containing hydrocarbon gases, for example. Sensors containing such elements have particular utility in the area of mining and oil drilling environments, as well as industrial, safety, and commercial applications.

Abstract: The present invention relates to an environmental condition sensor which is used to detect temperature etc., which sensor comprises an environmental condition sensor proper (1, 3,or 7), and a gas permeable structure (2 or 5) comprising .gamma.-MnO.sub.2, (Zn--Mn--FeO.sub.x) , and mAl.sub.2 O.sub.3.nCaO as the main composition thereof or an enamel layer (9) comprising .gamma.-MnO.sub.2, (Zn--Mn--FeOx), (.alpha.-Al.sub.2 O.sub.3.zeorite), and frit as the main composition thereof, which structure or layer surrounds the environmental condition sensor proper, so that carbon in oily smake and uncombustion gas striking the structure burns to prevent the oily smake and carbon from adhering to the environmental condition sensor proper (1, 3 or 7), whereby the degradation of the characteristics of the environmental condition sensor proper is avoided.

Abstract: Apparatus for the detection of carbon monoxide concentration of a gas. The apparatus comprises a base from which a pair of arms extend, a resistance layer disposed on each arm serving both to measure the difference in temperature between the arms and to heat a catalyst layer; a protective layer on the resistance layers to prevent electrical shorts caused by deposit of conductive particles in the gas to be detected; and a catalyst layer on one and only one of the arms in contact with the protective layer.

Abstract: A gas detector of the type using an electric heater in which a substrate consists of an upper film of electrically insulating substance having a resistance to heat and a lower film of substance different from the substance of the upper film, a recess is formed below or under the upper film by removing part of the lower film, and a film of electrically conductive substance is deposited over the bridge of the upper film across the recess in the lower film, thereby providing a heating element characterized in that said heating element consists of a film of a substance having catalytic effects in the presence of a gas to be detected deposited on said electrically conductive substance or a material responsive to a gas to be detected, or consists of said electrically conductive substance having catalytic effects in the presence of a gas to be detected or a substance containing said substance having catalytic effects in the presence of a gas to be detected or a substance responsive to a gas to be detected, and said

Abstract: An improvement is provided in a portable gas detector used to detect combustible gases, such as methane, which embodies a Wheatstone bridge circuit including a refractory-coated detector element having thereon a catalyst for promoting oxidation of the combustible gas to be detected constituting one leg of the bridge and a refractory-coated reference element constituting a second leg of the bridge. The improvement consists in the application of a cobalt oxide coating to the reference element, whereby the occurrence of spurious signals by the Wheatstone bridge circuit due to causes other than the presence of a combustible gas is greatly reduced, if not completely eliminated.

Abstract: An improvement is provided in apparatus used to detect combustible gases, which embodies a Wheatstone bridge circuit including a refractory-coated detector element having thereon a catalyst for promoting oxidation of the combustible gas to be detected constituting one leg of the bridge and a refractory-coated reference element constituting a second leg of the bridge. The improvement, in its broadest aspect, consists in using a mixture of palladium, palladium oxide and nickel oxide as the catalyst on the detector element. In addition, an improved reference element is provided which has a coating of either sodium metasilicate or lead borate deposited thereon.

Abstract: An insulating support body, for example an aluminum oxide ceramic, supports two electrodes spaced from each other by a small gap, for example 0.1 mm, which will have therebetween a high resistance. Upon collection of soot, the resistance between the electrodes across the gap will drop, which can be indicated by sensing current through the electrodes upon connection to a source of electrical energy. To remove soot upon termination of smoking, or soot contents in the gases, the electrodes are applied over, or embedded in a layer of essentially non-conducting catalyzing material which, in the presence of oxygen, catalyzes the oxidation of soot located in the gap between the electrodes to thereby remove the soot by oxidation and restore the resistance of the path between the electrodes and hence the sensitivity of the sensor for subsequent detection of accumulation of soot in the gap.

Abstract: Catalytic gas sensors comprise a noble metal filament onto which is applied alumina having a particle size of not greater than 100 A and a catalyst material is impregnated into the dried alumina. The alumina may be dried by passage of an electric current through the filament and, prior to coating the filament may be stabilized by coating with a thermally decomposable aluminium salt and decomposed by passing a pulsed electric current.

Abstract: A differential thermocouple hydrogen gas detector (10) is provided by coating one thermocouple junction (34) of a differential thermocouple pair (34, 36) with a Palladium-Silver alloy catalyst (46) and the other thermocouple junction (36) with a non-catalyst (52). Heated hydrogen gas reacts with the catalyst (46) to liberate heat to the catalyst coated thermocouple junction (34) in proportion to the concentration of hydrogen gas and proportionally raise the temperature of the catalyst coated junction (34) above that of the non-catalyst coated junction (36). The output signal (44) from the differential thermocouple device (34, 36) thus provides an output signal indicative of the concentration of hydrogen gas.

Abstract: Disclosed is a detector for fumes of hydrazine and its derivatives, methydrazine (MMH) and 1,1-dimethylhydrazine (UDMH). The detector encompasses a means for generating heat when fumes of hydrazine or its derivatives are catalytically decomposed after coming in contact with the active ingredient of the detector. The means for generating heat includes the active ingredient, iridium, which is deposited within and upon a ceramic pellet. The pellet is fitted with a thermal responsive means responsive to the generated heat. An output signal proportional to the generated heat can be interpreted by a balanced electronic bridge. The electronic bridge is balanced by preparing an unimpregnated pellet in the same way as the impregnated pellet and putting it in the circuit as a reference. The reference, being the same size and shape and prepared in the same manner, compensates for changes in temperature and other changes in the circuit, thus allowing one to zero the instrument.

Abstract: A sensor for the quantitative determination of reduction of a gas in which a thin tungsten oxide film detector element includes means for providing a specificity for the gas to be detected with respect to other gases. If ammonia is to be detected, a platinum catalyst is utilized. If hydrogen sulfide is to be detected, tungsten trioxide is used in the film.

Abstract: A microminiature palladium oxide gas detector and its method of manufacture. The detector comprises an extremely small coil of extremely fine wire such as platinum which is retained, sealed and insulated with an amorphous ceramic binder. The detector further comprises a catalyst applied to its exterior surface. The detector is manufactured by winding the wire about a mandrel which is desirably molybdenum. The coil is then coated with the binder composition which preferably comprises reduced chromic and phosphoric acids. The binder is then cured to retain the coil and the mandrel is removed by etching or oxidation. The catalyst is then applied which is preferably palladium nitrate in a weakly acidic hydrolyzed solution which has been adjusted to a pH of about 3 with tertiary octyl amine. The catalyst is then dehydrated and calcined desirably using an automatic electronic pulse controlled machine to precisely adjust and control processing temperatures and times.

Abstract: A method and apparatus for determination of oxygen or hydrogen levels in a gas sample. In accordance with the method, a flowing stream of a gas sample containing a minor amount of diluent gas, oxygen and/or hydrogen is provided. A predetermined amount of a gaseous fuel is combined with the flowing stream of the gas sample to provide a reactive mixture. The reactive mixture is passed over a first sensing element and over a second sensing element. Prior to passing the flowing stream of the gas sample over the second sensing element, the stream is passed over a catalyst to cause reaction of oxygen and/or hydrogen with the fuel to produce water and heat. This causes a temperature and a moisture differential to exist between the first sensing element and the second sensing element. The difference in the moisture level or the temperature differential is converted to an electric signal. The electric signal produced is compared with a reference standard whereby the level of the oxygen and/or hydrogen is determined.

Abstract: A catalytic gas detector is formed as a sandwich and comprises two flat printed film resistance thermometer sensors back-to-back with a layer of thermally insulating material between them. A coating of a suitable catalytic substance covers an exposed flat face of one of the two sensors.

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.

Abstract: The device of this invention is used to detect small quantities of liquid emical agents in certain pesticides on the basis of the heat reaction between the liquid agent and a chemical oxidant such as sodium or calcium hypochlorite. The detecting device consists of a thin film of resistance heat sensitive element on top of which porous or fibrous substrate material is mounted. This substrate is impregnated with the oxidant material. As a liquid agent contacts substrate it permeates through the substrate and reacts with the oxidant and generates heat. The output volume from the thin film resistance element increases correspondingly. The time from agent contact until this signal is observed as tested is less than one (1) second. The method is directed to the contacting of the liquid agent against the surface, wherein it permeates through the substrate and reacts with the oxidant and generates heat which change in heat is detected by the detecting device.