Abstract: A gas sensor including a substrate, a heater formed on said substrate, and a gas sensing material to be heated by said heater, wherein the area of the substrate under the heater is removed or reduced in its thickness to form a cavity. The thickness of the layer of the gas sensing material is reduced gradually toward the peripheral of the gas sensing material.

Abstract: In a gas sensor comprising a housing and having driver and amplifier circuits the housing has a bottom part with at least four cavities arranged in radial symmetry around a central gas admission space from which gas admission passages of the same shape and size extend radially outwardly to the various cavities for supplying gas to be measured to surface wave components of which one is disposed in each of the cavities and the cavities have discharge passages extending outwardly and having all the same gas flow resistance for the discharge of the gases from the housing cavities.

Abstract: A resistive gas sensor has a porous semiconducting oxide body in which the pore surfaces are decorated with a precious metal. The sensor operates at ambient temperatures for detection and measurement of target gases, especially carbon monoxide. The porous sensor body is formed of primary crystallites agglomerated together, the agglomerate size being less than 10 times the primary crystallite size, and the primary crystallite size having an average diameter of less than 5 micrometer. From 0.05 to 80% of the pore surfaces are covered by the metallic phase, the metallic phase consisting of particles having an average size of less than 50 nanometers. Presence of the target gas is indicated by a change in electrical resistance of the sensor.

Abstract: A resistive gas sensor having a WO.sub.3 sensing element is especially useful for detection of low concentrations (1 ppm or less) of ozone in air. The WO.sub.3 element is a porous layer with a 30-60% porosity and less than 50 micrometer thick, having in general a sufficiently open porous microstructure and high surface area to give satisfactory response to ozone. The sensor is used for detection of low ozone concentrations at a working temperature in the range from ambient to 600.degree. C.

Abstract: A nitrogen oxide sensor and a method of manufacturing the sensor are disclosed. The sensor has a gas detecting portion including sensitive material having electric property thereof subject to change in association with presence of nitrogen oxide in gas and a pair of electrodes electrically connected with the gas detecting portion. The gas detecting portion includes, as a main component thereof, metal oxide compound represented by a general formula:Bi.sub.2 Sr.sub.2 (Ca.sub.1-x Y.sub.x)Cu.sub.2 O.sub.8+y(0.8.ltoreq.x.ltoreq.1; 0.ltoreq.y.ltoreq.1)and having the 2212 phase crystal structure and crystalline size greater than 100 .ANG..

Abstract: A method of monitoring hydrocarbons concentration in an exhaust gas includes the steps of: sampling exhaust gas on a vehicle, isolating the hydrocarbons from the exhaust gas on a vehicle, and measuring the amount of hydrocarbons isolated from the sample on a vehicle and providing an indication based on the amount of hydrocarbons. A sensor assembly for monitoring the concentration of hydrocarbons in an exhaust gas of a vehicle includes: a hydrocarbon absorbing material placed in a stream of gas on a vehicle, a gas sensor operatively connected with the absorbing material and in the stream of gas and producing a gas signal, and a sensor controller connected to the gas sensor for receiving the gas signal and for determining the amount of hydrocarbons.

Abstract: The previously presented teaching of the invention describes a method for the evaluation of sensor signals with the purpose of producing plausible and physiologically satisfying switching impulses for interrupting or for opening the air supply in ventilation systems, particularly for the ventilation of passenger cabins in motor vehicles, depending on the pollutant content of the ambient air established by one or more sensors.

Abstract: A gas sensor, suitable for use under non-steady state conditions, has a gas-sensitive resistor with pairs of electrodes which either have different spacings between the electrodes of a pair, or comprise a pair at the active surface and further pairs buried in the resistor at different distances from the active surface. The sensor can be used in place of a sensor array, and is coupled to a processor for processing the resistance signals to detect and/or measure at least one target gas. The sensor is self-diagnostic, and factors such as relative humidity and ambient oxygen, that can otherwise affect the readings, can be compensated for without the aid of additional sensors for that purpose.

Abstract: An integrated airway adapter capable of monitoring CO.sub.2 concentration in real time, breath by breath using infrared absorption techniques and monitoring respiratory flow with differential pressure flowmeters under diverse inlet conditions through improved sensor configurations which minimize phase lag and dead space within the airway adapter.

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: An in-line gas monitor capable of accurate gas composition analysis in a continuous real time manner even under strong applied vacuum conditions operates by mixing an air sample with helium forming a sample gas in two complementary sample loops embedded in a manifold which includes two pairs of 3-way solenoid valves. The sample gas is then analyzed in an ion trap mass spectrometer on a continuous basis. Two valve drivers actuate the two pairs of 3-way valves in a reciprocating fashion, so that there is always flow through the in-line gas monitor via one or the other of the sample loops. The duty cycle for the two pairs of 3-way valves is varied by tuning the two valve drivers to a duty cycle typically between 0.2 to 0.7 seconds.

Abstract: A gas analyzing apparatus includes a sample gas line with a sample line valve for providing a sample gas, and a reference gas line with a reference line valve for providing a reference gas. A first gas analyzer is connected to the sample line downstream of the sample line valve, and a second gas analyzer is connected to both the sample and reference gas lines downstream of the valves. The lines are configured such that sample gas and reference gas may be alternately provided to the second gas analyzer either directly or indirectly via the first gas analyzer.

Abstract: The present invention provides an apparatus for the analysis of mixed gas components which can perform, in high precision, determination of the quantities of components contained in a sample gas containing a plurality of the components having molecular weights close to each other and which has a Fourier transform mass spectrometric means for ionizing a sample gas, applying a high frequency electric field to the ionized gas to induce cyclotron resonance, detecting the cyclotron resonance as a high-frequency decaying electric signal, and converting the resulting high-frequency decaying electric signal to a frequency-domain signal and a wavelength variable light irradiating means for irradiating a light of a single wavelength to ionize the molecules of the components constituting the sample gas, said irradiating means being able to vary the wavelength and/or intensity of the irradiation light.

Abstract: An acoustic cell includes multiple acoustic cavities fluidly coupled together. At least two of the acoustic cavities have unequal lengths and cross sections. End segments of the acoustic cell are uniformly cylindrically shaped or conically shaped. A driver transducer at one end of the acoustic cell and a receiver transducer at another end of the acoustic cell are acoustically isolated from the acoustic cell. A pair of preferably metallic isolation diaphragms transmit acoustic signals to and from the transducers without significantly altering the phase-frequency characteristics of the acoustic signals. The acoustic cell operates as an acoustic resonator operating at frequencies lower than any possible self-resonance frequencies of the isolation diaphragms or the driver and receiver transducers. When a binary gas is flowed through the cell, a processor detects a resonant frequency of the gas within the cell to determine a composition of the gas.

Abstract: An exhaust gas sensor has first and second sensor elements. Exhaust gas surroundings of the first sensor element are catalytically activated, so that an oxygen partial pressure which is in equilibrium will always be measured by the first sensor element, regardless of the conversion capability of a catalytic converter. The exhaust gas surroundings of the second sensor element are separate from the exhaust gas surroundings of the first sensor element, so that the exhaust gas surroundings of the second sensor element are not catalytically active. As a function of the conversion capability of the catalytic converter, the second sensor element measures either an equilibrium oxygen partial pressure or a free oxygen partial pressure, which are of different magnitudes. A malfunction of the catalytic converter is detected by comparing measurement signals of the first and second sensor elements.

Abstract: A gas detector is disclosed which includes a CO sensor and a processor. The CO sensor senses an environmental CO concentration and provides a variable electrical output in response. The processor receives digitized samples of the sensor's electrical output and computes, with each measurement sample, a COHb level of a hypothetical person exposed to the CO concentration sensed. The computation involves determining an equilibrium COHb level for each measurement sample, which is compared with a previously computed COHb level associated with previously measured samples. The previously computed COHb level is updated based on the comparison. When the computed COHb level is above a predetermined danger threshold, the processor preferably causes an audible and visual alarm to be activated to alert any persons present. The gas detector can further include a CH.sub.4 sensor coupled to the processor for independently sensing CH.sub.4 levels such that an alarm is activated when the CH.sub.

Abstract: Disclosed is a method and a sensing device capable of measuring a predetermined measurement gas component continuously and accurately with good response over a long period of time without being affected by a high oxygen concentration in a measurement gas. The measurement gas is introduced into a first processing zone. A first electrochemical pumping cell is used to lower a partial pressure of oxygen in an atmosphere thereof to a degree sufficient to control a partial pressure of oxygen in a subsequent second processing zone. The gas is introduced into the second processing zone. Oxygen in an atmosphere is pumped out by using a second electrochemical pumping cell so that the partial pressure of oxygen in the atmosphere is controlled to have a low value of partial pressure of oxygen which does not substantially affect measurement of an amount of the measurement gas component. The gas is introduced into a third processing zone.

Abstract: There is provided an emission testing system which maintains system integrity and which can be manufactured at less cost than current standard emission testing systems. The system includes a sampling unit for collecting emissions from a vehicle and diluting the collected emissions with background ambient air as required and means for drawing a proportional test sample from the bulk air/emission mixture. The analyzer is a single unit which includes a reaction cell for chemiluminescence reactions and a combustion cell for flame ionization analysis. In addition the system includes a common sample conditioning for the test sample prior to splitting the test sample for chemiluminescence and flame ionization analysis.

Abstract: A monitoring device system and a method for controlling ventilation in an enclosed or confined environment by regulating the effective ventilation rate, air exchange rate, mixing factors, stratification of air within the confined area, the percentage of outside air which is introduced (when possible), the percentage of recirculated air, mean air life, air half-life are described. The device may be used for controlling an HVAC system so that air quality conforms to predetermined air quality standards. The monitoring device consists of a multiport sample collection system and one or more sensors to detect determinants of air quality. The method of control uses a CPU to regulate fans, dampers, and other systems to maintain the air quality within predetermined ranges, based upon the monitoring data. A tracer gas, preferably CO.sub.2, is used to determine system parameters.

Abstract: A gas sensor has a gas sensing component which permits measurement of a change in optical absorption and, optionally also a change in electrical conductivity on exposure to an environment containing certain gases. The gas sensing component comprises a metal bis aromatic macrocycle which may be a new mixed rare earth metal bis tetrabenzoporphyrin or tetrabenzoazaporphyrin.

Abstract: A method of manufacturing a nitrogen oxide sensor for detecting a nitrogen oxide to be used in the field of e.g. reducing or decomposing nitrogen oxides, as well as such sensor and material suitable for manufacturing the sensor are disclosed. For manufacturing the sensor material, a precursor containing components for constituting the sensor material in a predetermined equivalent ratio of stoichiometry between chemical elements is prepared. First, the precurser is subjected to sintered to a preliminary sintering step. Then, the resultant sintered material is subjected to at least two cycles of main sintering step at 815.degree. to 848.degree. C. (T1) with an intermediate grinding step of the sintered material therebetween, thus obtaining the gas detecting portion comprised mainly of oxide compound having a composition represented by:Bi.sub.2 Sr.sub.2 YCu.sub.2 O.sub.8+y(0.ltoreq.y.ltoreq.1)and having the 2212 phase of crystal structure.

Abstract: A planar palladium structure makes use of the unique properties of palladium to provide a hydrogen permeable membrane suitable for use in providing, for example, selective control of a nominal gas pressure within a cavity. The contemplated planar palladium structure includes a planar substrate having upper and lower major surfaces and an array of microfine channels therebetween, wherein the channels allow gaseous communication between the upper and lower major surfaces, and an array of palladium deposits being distributed on the substrate and located with respect to the microfine channels so as to restrict the gaseous communication to diffusion of hydrogen gas.

Abstract: A gas sensor has at least a measuring electrode and a counter electrode on an electrolyte layer. This gas sensor is improved with respect to the complete extent of the electrochemical reaction achieved of the gas molecules, which are to be detected, at the measuring electrode by the manner of determining an electrical charge developed or accumulated thereat. To solve this task, the invention provides that the measuring electrode (14) has component electrodes (14a, 14b) which enclose the electrolyte layer (11, 12) in the manner of a sandwich.

Abstract: Provided is a novel method for rapidly determining an impurity level in a gas source. A gas source and a measurement tool are provided for measuring an impurity level in a gas flowing from the gas source. The measurement tool is in communication with the gas source through a sampling line. The sampling line has a gas inlet disposed upstream from a gas outlet. The sampling line is baked according to a baking strategy, such that when baking is terminated, a concentration profile of the impurity in the sampling line contains a first region and a second region. In the first region, extending from the gas inlet to a point downstream from the inlet, the vapor phase concentration of the impurity is less than the vapor phase concentration of the impurity in the gas entering the sampling line.

Abstract: A gas concentration sensor for use in a closed container having a constant volume and gas within the container, wherein the gas has a known pressure at a given temperature. The sensor includes a pressure sensing device disposed within the container, wherein the pressure sensing device generates a first electrical signal functionally related to the gas pressure within the container. The sensor also includes an electronic circuit connected to the pressure sensing device which amplifies the first electrical signal and produces a second electrical signal functionally related to the gas concentration within the volume at any temperature.

Abstract: A method and apparatus for controlling the temperature in a kiln in which cement clinker is manufactured. The temperature is controlled by controlling the fuel rate to the kiln. The fuel rate is adjusted according to a calculation that is made of the sulphur evaporation in the kiln, thereby obtaining a measure of the instantaneous temperature in the burning zone. The evaporation factor is calculated on the basis of measurements of the sulphur content in the cyclone material which passes to the kiln or a measurement of the sulphur content in the exit gases out of the kiln.

Abstract: A hydrocarbon gas detection device operates by dissociating or electro-chemically oxidizing hydrocarbons adsorbed to a silicon carbide detection layer. Dissociation or oxidation are driven by a varying potential applied to the detection layer. Different hydrocarbon species undergo reaction at different applied potentials so that the device is able to discriminate among various hydrocarbon species. The device can operate at temperatures between 100.degree. C. and at least 650.degree. C., allowing hydrocarbon detection in hot exhaust gases. The dissociation reaction is detected either as a change in a capacitor or, preferably, as a change of current flow through an FET which incorporates the silicon carbide detection layers. The silicon carbide detection layer can be augmented with a pad of catalytic material which provides a signal without an applied potential. Comparisons between the catalytically produced signal and the varying potential produced signal may further help identify the hydrocarbon present.

Abstract: The present invention is a carbon monoxide or other toxic gas detector. The detector of the present invention detects the presence of carbon monoxide in an air sample by measuring the time required for the sensor circuitry to charge. Such a measurement technique eliminates the inaccuracies inherent in prior art detectors which measure the resistance of the sensor circuitry upon exposure to carbon monoxide. The detector of the present invention is controlled by a microprocessor which enables the detector to retain in memory air sample readings of carbon monoxide or other toxic gas. If the detector registers four consecutive readings which indicate the presence of carbon monoxide in an air sample in a concentration greater than or equal to about 100 ppm, then the alarm of the detector will be triggered, thereby alerting the user to a dangerous concentration of carbon monoxide gas in the air.

Abstract: A hydrogen sensitive metal alloy contains palladium and titanium to provide a larger change in electrical resistance when exposed to the presence of hydrogen. The alloy is deposited on a substrate and a thin film and connected across electrical circuitry to provide a sensor device that can be used for improved sensitivity and accuracy of hydrogen detection.

Abstract: An electrochemical gas sensor assembly comprises an electrochemical gas sensor (1) including sensing (39) and counter (32) electrodes, an intervening body of electrolyte contacting the electrodes, and means (5) for controlling the diffusion of gas to the sensing electrode. A test gas generator (7) is connected to the sensor so as to supply a test gas directly to the sensing electrode (39) by-passing the gas diffusion control means (5).

Abstract: Sample analysis in a portable analytical instrument, preferably in the form of a gas chromatograph, benefits from temperature control of one or more thermal zones in the instrument by way of a thermal isolation system that includes a novel pumping assembly to effect a selective amount of thermal isolation of the thermal zone. The pumping assembly includes a pumping element in the form of a tubular or planar palladium structure. The pumping assembly makes use of the unique properties of palladium to allow selective control of a nominal gas pressure within a vacuum cavity. A component system, which may include a separation column and a thermal device for heating and/or cooling the component system, may be provided within the vacuum cavity. The thermal device and the pumping assembly are individually controlled by a control system.

Abstract: A gas detecting system for classifying the type of liquid fuel in a container or tank. The system includes a plurality of semiconductor gas sensors, each of which differs from the other in its response to various organic vapors. The system includes a means of processing the responses of the plurality of sensors such that the responses to any particular organic substance or mixture is sufficiently distinctive to constitute a recognizable "signature". The signature of known substances are collected and divided into two classes based on some other known characteristic of the substances. A pattern recognition system classifies the signature of an unknown substance with reference to the two user-defined classes, thereby classifying the unknown substance with regard to the characteristic of interest, such as its suitability for a particular use.

Abstract: A device for the selective detection of a component from a gas mixture comprises a selective prefilter for retaining the other components of the gas mixture, a measuring unit arranged downstream of the selective prefilter for the component to be detected, and a pump pumping the gas mixture. The use of a photoionization detector as a downstream measuring unit makes possible a continuous display operation.

Abstract: An ozone concentration sensor for use with an ozone generator. The ozone free feed gas to the ozone generator is briefly fed to the sensor which measures both the temperature of the feed gas and the time it takes a high frequency sound pulse to travel a predetermined distance in the feed gas for reference date. A portion of the output gas from the ozone generator is then fed to the sensor and the same measurements are made for the output gas. A programmed microcomputer determines the ozone concentration in the output gas from the measurements. In one embodiment, the sensor constantly receives output gas from the ozone generator. The reference measurements are made while operation of the ozone generator is briefly interrupted and feed gas passes through the ozone generator unchanged. Reference measurements may be stored and used for repeated ozone concentration calculations, so long as there is no significant change in the feed gas.

Abstract: A method for identifying a single fuel vapor in an atmosphere of interest that is selected from the group consisting of at least two fuels and that is the sole fuel component of the atmosphere, comprising the steps of: providing a plurality of measuring means that are at least equal in number to the types of fuels that compose the fuel group and which have different sensitivities to the respective fuel vapors; presetting the relationship between the magnitudes of the outputs from the respective measuring means at various fuel vapor concentrations in such a manner that it differs from one fuel vapor to another; placing said measuring means in the atmosphere of interest containing said single fuel vapor as the sole fuel component; measuring the concentration of that fuel vapor; determining the relationship between the magnitudes of outputs as obtained from the respective measuring means; and comparing the thus determined relationship with the preset relationships, thereby identifying the fuel vapor in the atmos

Abstract: A method and apparatus for detecting methane in a gas mixture that may contain commonly used solvents including alcohols and acetones is provided which measures a change in electrical resistivity, electrical conductivity or relative permeability caused by the presence of methane gas at a chemically active sensing structure. The apparatus includes two spaced-apart electrodes that are covered with a thin methane-sensitive semi-conductive metal oxide layer. The gas to be tested is heated to a temperature exceeding 740.degree. C. before it contacts the metal oxide layer. Alcohols, acetones and other solvents are oxidized to electrical carbon dioxide and water before they reach the metal oxide layer so that only the less reactive and reducing gas methane reaches the metal oxide layer where it is reduced and increases the conductivity of the metal oxide layer as measured between the two spaced-apart electrodes with an appropriate electrical meter instrument.

Abstract: Apparatus to measure the calorific value and/or the Wobbe index of fuel gas supplied along a pipe. A control can operate two outlet valves and cause an inlet valve to be locked in a closed position or be unlocked to stay in a normally open state until the gas pressure in a chamber of predetermined volume reaches a preset pressure difference above the pressure in the pipe. Under direction of the control, a pump moves fuel gas from the pipe into the chamber whilst the outlet valves are closed. Once the pressure in the chamber attains the preset difference, the inlet valve closes automatically to be held locked closed by the control. Certain properties of the gas in the chamber, such as thermal conductivity, specific heat capacity and speed of sound, are measured and corrected to STP conditions. The pump moves two samples of gas into the chamber at two sequential times, each time until the gas pressure therein attains the preset value and the inlet valve again closes automatically in a locked position.

Abstract: A sensor to detect gases and vapors, particularly carbon monoxide and water vapor, at relatively low concentrations includes a substrate having a layer on a face of the substrate. The layer comprises a semi conductor metallic oxide (such as stannic oxide), a catalyst (such as platinum black), and a rheological agent (such as kieselguhr or sepiolite). The rheological agent induces porosity into the surface of the layer. The rheological agent affects the mixing and processing of the layer, and aids binding, resulting in a sensor with greater sensitivity and faster response.

Abstract: A gas sensing apparatus is disclosed including a gas sensing device that is self-heated due to an applied voltage, whose resistance variation amount is varied to thereby sense gas; a voltage supply for variably supplying a voltage to the gas sensing device; a current detector for detecting the current flowing through the gas sensing device thereby generating a current-voltage characteristic for the gas sensing apparatus under the effect of a given gas exposure; and a control and judgement portion for controlling the voltage supply to control a variation value of a voltage supplied to the gas sensing device and to determine the kind and density of a gas in an ambient atmosphere, using current-voltage characteristic reference data.

Abstract: In an oxygen gas sensor having a variable electrical characteristic dependent upon ambient oxygen concentration, a ceramic holding member having a hole for holding a plate sensor sensor element is disposed in a housing with the element inserted into the housing. During sensor assembly, powder is filled under pressure in the housing between a pressurized member and the ceramic holding member. The ceramic holding member has an inclined surface descending directly from an upper opening end of the holding hole to form an obtuse angle between the sensor element and the inclined surface, so that the powder can flow on the inclined surface smoothly during the powder filling and powder compressing operations. By taking this construction it is possible to provide an oxygen concentration sensor with no cracking of the element and easy mounting of the sensor element to the housing.

Abstract: An early warning system for providing notice that seismic activity, such as an earthquake, is imminent. The earthquake early warning system includes a subterranean detector unit assembly having a plurality of detector units carried by a subterranean inverted conduit. The conduit is filled with a dense, dry inert aggregate and has a soil interface consisting of a perforated metal screen or porous fabric material thus allowing migrating gases to migrate into the conduit. Gas detectors carried by the conduit detect the gases as they migrate into the conduit. Access tubes are provided to allow access to the detectors from the surface of the ground without exhuming the conduit assembly. The conduit would carry a plurality of detectors and associated access tubes for monitoring migration of gases across a linear distance. The detectors are in communication with a monitoring facility for monitoring the rate of migration of gases.

Abstract: A gas sensor for detecting a gas component from a food item includes a sensing layer having an electrical resistance value that varies in accordance with the concentration and type of the gas component generated from the food item to thereby sense the gas component, first and second electrodes coupled across the sensing layer and connected to a power supply, a heater for heating the gas sensor to a temperature of sensing operation, and a switch connected to an adjustable voltage supply for controlling whether the heater is operated in a first temperature range or in a second temperature range. The sensing layer includes a mixture of SnO.sub.2 and WO.sub.3 in a predetermined ratio.

Abstract: A carbon monoxide sensor (40) has a substrate arranged with other adjacent or overlaid layers attached thereon (41) defining a first space (43a) into which a unknown gas or gas mixture is introduced into and a second space (43b) communicating with the first space. A carbon monoxide adsorbent (61) is disposed in the second space, and an electrode (56) detects a partial pressure of oxygen in the carbon monoxide adsorbent. A pump cell includes the cell part (42), made of a solid electrolyte conducting oxygen ion, and a pair of electrodes (51, 52). The pump cell substantially removes oxygen from a gas in the first space (43a) while carbon monoxide in the gas is adsorbed onto the carbon monoxide adsorbent (61). Then, the pump cell introduces oxygen into the first space (43a), and a time is measured that the oxygen diffuses from the first space (43a) to the first detecting electrode (56) through the adsorbent (61).

Abstract: A gas measurement system includes a first test unit for measuring the concentration of a selected gas at a first location, a second test unit for measuring the concentration of the selected gas at a second location, and a comparator for comparing the measured concentration of the selected gas from the first location with the measured concentration of the selected gas from the second location. An alarm indication is provided when a difference between the first and second measurements is greater than a user defined value or percentage. In an exemplary embodiment, the gas measurement system is configured to detect an ozone leak.

Abstract: The present invention relates to a gas sensor and a gas discriminating method which are capable of distinctly discriminating two or more kinds of gases. A DC bias and AC signals which are superposed to a junction part, which is formed on a gas sensor having a p-type oxide semiconductor and an n-type oxide semiconductor by means of heterojunction of end surfaces thereof, an impedance characteristic of the junction part is measured, and CO gas and H.sub.2 gas are discriminated in accordance with a dependence on a frequency of the AC signals and on the DC bias of the impedance characteristic. CuO into which an alkali metal element is doped is used as the p-type oxide semiconductor and ZnO is used as the n-type oxide semiconductor. The alkali metal element to be used is an alkali metal element selected from the group of Li, Na and K and the doping quantity is such that 0.2 mole %.ltoreq.M.sub.2 O.ltoreq.5 mole %, where M is Li, Na or K.

Abstract: An explosive detection screening system used for the detection of explosives and other controlled substances such as drugs or narcotics. The screening system detects the vapor and/or particulate emissions from the aforementioned substances and reports that they are present on an individual or object and the concentration of each substance detected. The screening system comprises a sampling chamber for the collection of the vapor and/or particulate emissions, a concentration and analyzing system for the purification of the collected vapor and/or particulate emissions and subsequent detailed chemical analysis of the emissions, and a control and data processing system for the control of the overall system.

Abstract: An oxygen sensor probe for a boiler including a U-shaped zirconia element that is to be brought in contact with an exhaust gas in the interior of a cylindrical probe body attached to a plug and arranged together with a thermocouple in the longitudinal direction of the body. A heater for heating the element is provided around the periphery of the element and a protective filter is provided on the top portion of the body. The probe is characterized by the U-shaped zirconia element 11 being located at an upper end of the probe body 12 with its concave open portion 11' facing upwards to be contacted with the exhaust gas while its convex closed portion 11" faces downward to be confronted with the thermocouple 16.

Abstract: An improved sensor support subassembly for a chemical sensor in the testing of gaseous emissions. The sensor support subassembly of the present invention comprises means for slideably engaging a sensor unit with a gas intake manifold block. The sensor unit comprises a cylindrical base which forms the inlet to the sensor. The manifold block comprises a gas intake means, a gas channel and a U-shaped slot for slideably engaging the sensor unit's cylindrical base within the manifold block such that an air-tight passage is formed between the sensor inlet and the gas channel. The sensor support subassembly also provides a sealing means for ensuring an air-tight seal between the sensor unit and the manifold block. This slidable engagement scheme allows the sensor unit to be rotated about the axis of the cylindrical base, which in turn facilitates the use of a card-edge connector for making the electronic connections between the sensor and the sensor testing system power and data lines.

Abstract: Methods for measuring the surface area of a top region of a silicon wafer by initially depositing a monolayer of hexamethyldisilizane over the surface area of the silicon wafer. The silicon wafer is then positioned within a vacuum environment. Next, oxygen is introduced into the vacuum chamber so that the HMDS substantially reacts with the oxygen to form products such as carbon dioxide and water. At least one of the water and the carbon dioxide are measured from the known volume of the vacuum chamber. Based on the amount of product formed, the amount of HMDS covering the surface area is determined. Finally, from the amount of HMDS calculated to be originally positioned on the surface area, a value for the surface area is determined.

Abstract: A measuring assembly is described for studying gaseous media, in which a measuring cell (20) connected to a circuit board (40) is clamped into a receptacle (10). The receptacle (10) includes a base plate (11), a pressure plate (30), arms connecting base plate (11) and the pressure plate (30) with each other, i.e., a stud bolt (13) and a connecting arm (14), as well as a pressure spring (16) acting on the pressure plate (30). The pressure plate (11) is supplemented by a chamber cover (15) so as to form a gas chamber (17). Preferably, a filter (50) is located between the base plate (11)/chamber cover (15) and the measuring cell (20).