Abstract: An alumina substrate has a front surface with a semiconductor gas sensor main body attached thereon for specific detection of a surface exposed gas, and has a rear surface formed with a glass layer and a gold paste layer as superposed on the surface, and bonded to a gold plating layer on a frame by parallel gap welding. The gold paste layer is welded to the gold plating layer with the heat of welding. The glass layer prevents transmission of thermal impact of die bonding to the substrate.

Abstract: A method for producing a silica mask on metal oxide surface is disclosed. Benzaldehyde is adsorbed on neutral or weak alkaline metal oxide surface, and then tetra-methoxy silane is deposited. The tetra-methoxy silane is hydrolyzed by water vapor into silica and the adsorbed benzaldehyde is removed by NH3 as benzo-nitrile. Thus a silica mask is produced on the metal oxide surface, and the mask has vacancies corresponding to the removed benzaldehyde. The vacancies act as the adsorption sites for shape selective adsorption.

Abstract: In an air conditioner control device, edges of change of the sensor outputs are detected by the second derivative of the outputs of WO3 gas sensor for NOx detection. The edge represents that the sensor is exposed to diesel exhaust. Its response to diesel exhaust is quick and it does not affected much by the influence of the wind. When the edge is detected, an intake of an automobile ventilator is dosed and the inflow of contaminated outdoor air is interrupted. An AD convertor stored micro computer is used for processing the sensor signal. In order to compensate the shortage of resolution of the AD convertor, the outputs are first differentiated analogically, then amplified and converted to digital signals, and finally further differentiated digitally.

Abstract: A method of and a system for detecting a gas. A histogram of gas sensor outputs in the past is prepared to determine a gas detection threshold value from the histogram. The threshold value is determined, for example, based on the modal sensor output on the histogram. The threshold value is modified based on the width of distribution on the histogram since the width represents the degree of pollution of the background.

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: A BaSnO.sub.3 exhaust gas sensor and a process for producing the same. Surface reformation of sensor electrodes is done for preventing the deterioration of the sensor response and the corrosion of the electrodes by the Sn in the BaSnO.sub.3. After depositing an oxide film such as La.sub.2 Ti.sub.2 O.sub.7 or MgO on the surface of the electrodes, the electrodes are embedded in BaSnO.sub.3, and the BaSnO.sub.3 is sintered. Through the sintering process, the film of La.sub.2 Ti.sub.2 O.sub.7 or MgO is converted to a conductive complex oxide film by reacting with BaSnO.sub.3. The resultant film contains Ba and Sn elements. CaSnO.sub.3 and SrSnO.sub.3, which are homologous compounds of BaSnO.sub.3, are usable in place of BaSnO.sub.3.

Abstract: When the output of a gas sensor is approximately constant, the sensor output is stored as a reference output. Evolution of a gas is detected from variations in the sensor output from the stored reference output. The sensor output which is constant is detected by establishing that the difference between a maximum and a minimum of sensor output in a predetermined section is not greater than a specified value.

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 system for controlling an air cleaner having high ability to remove smoke but low ability to remove gas with use of a gas sensor having higher sensitivity to gas than to smoke. The air cleaner is brought into operation when the gas sensor detects the gas released with the occurrence of smoke. The progress of removal of smoke is detected from the saturation of the gas sensor output, whereupon the cleaner is brought out of operation. Preferably, the air cleaner is held in operation for a predetermined period of time after the detection of the saturation to fully remove the smoke.

Abstract: An exhaust gas sensor in which a metal oxide semiconductor containing at least one member of a group of elements consisting of Sn, Fe, Ni and Co and Pt electrodes having ZrO.sub.2, deposited in the grain boundary are used. Such metal oxide semiconductors include, for example, SnO.sub.2, BaSnO.sub.2, BaSnO.sub.3, SrSnO.sub.3, and CaSnO.sub.3. The exhaust gas sensors are manufactured by mixing such compounds as BaCO.sub.3, SrCO.sub.3 or CaCO.sub.3 with SnO.sub.2 in equimolar ratio to react them in air at 1200.degree. C. for four hours. The compounds thus obtained were pulverized and Pt electrodes with ZrO.sub.2 were imbedded therein, then were molded into sensor chips. The chips thus molded were baked by heating in air. After the chip has been sintered the exhaust gas sensor was assembled. It comprised an insulating substrate of alumina, etc. having a recess provided at one end thereof in which the aforementioned sensor chip was housed.

Abstract: A gas sensor in which a compound of rhenium is added to tin oxide (SnO.sub.2). Rhenium inhibits the sensor from lowering its resistance over time and in particular increases its durability against overheating. Rhenium is preferably used together with vanadium. Rhenium is preferably added by impregnation in order to maintain temperature characteristic of the sensor.

Abstract: A proton conductor gas sensor operable at room temperature for detecting hydrogen or carbon monoxide, and a gas detecting method using the sensor. A pair of electrodes connected to a proton conductor are short-circuited to cause protons to travel through the conductor utilizing the difference in activity between the electrodes or the difference in gas permeability between the electrode and an atmosphere containing the gas to be detected. The potential difference produced in the interior of the conductor by the travel of the protons is obtained as the output of the sensor. This output is in proportion to the concentration of the gas and low in humidity dependence.

Abstract: An exhaust gas sensor including a compound ASnO.sub.3-.delta. wherein A is Ba, Ra, Sr or Ca to make use of the variation of resistance value of the compound. BaSnO.sub.3-.delta. and RaSnO.sub.3-.delta. are n-type semiconductors, while SrSnO.sub.3-.delta. and CaSnO.sub.3-.delta. exhibit the behavior of n-type semiconductors at the point of equivalence and the behavior of p-type semiconductors in the lean burn region. The compound ASnO.sub.3-.delta. is prepared by reacting an alkaline earth with SnO.sub.2.

Abstract: A .lambda. sensor comprising a perovskite compound ASnO.sub.3-.delta. and silica, germania, zirconia or hafnia added to the compound in an amount of 0.5 to 30 mol % per mol of the compound. Silica or like additive gives improved oxygen sensitivity and reduces the temperature dependence of the oxygen sensitivity.

Abstract: A combustion gas sensor and material therefore responsive to changes in the composition of ambient atmospheres wherein the sensing element includes SnO.sub.2 crystals having a mean d of approximately 500-3200 .ANG. and having a surface area to mass ratio S of 1-8 m.sup.2 /g a process for making same. Preferably, the standard deviation of crystal size distribution is 0.2d.

Abstract: A combustion gas sensor and material therefore responsive to changes in the composition of ambient atmospheres wherein the sensing element includes SnO.sub.2 crystals having a means d of approximately 500-3200 .ANG. and having a surface area to mass ratio S of 1-8 m.sup.2 /g a process for making same. Preferably, the standard deviation of crystal size distribution is 0.2d.