Abstract: A MEA 6 having a proton conductive membrane is sandwiched by metal plates 14, 15 and they are further sandwiched by heat pressable films 20, 21. An opening 24 and an opening 18 are formed in the heat pressable film 20 and the metal plate 14, respectively so that an electrode 10 is used as the sensing electrode and exposed to atmosphere to be measured. Openings 25, 19 are formed in the heat pressable film 21 and metal plate 15, respectively so that an electrode 11 is used as the counter electrode, and water vapor is supplied to the electrode from a water pack.

Abstract: A proton conductor gas sensor whose durability at high temperature is enhanced by using gel not converted to sol even at high temperature in a water reservoir. Fine particles of silica are gelled by adding water thereto and agitating the mixture under shear force. The thus obtained gel (34) is placed in a water reservoir of proton conductor gas sensor (2) and fed through steam introduction port (30) to MEA (10).

Abstract: An aqueous solution of a Na salt of a phenol sulfonic acid polymer as a liquid electrolyte is held in a separator of a liquid electrochemical gas sensor. A sensing electrode and a counter electrode are connected to the separator to detect CO at a range from about ?40° C. to about 70° C.

Abstract: Water is stored in a metal can, and water vapor is supplied to a separator through an opening in a washer. The separator is an alkali metal salt in a sulfonated synthetic resin membrane, and KOH aqueous solution is used as the electrolyte, and the sensing electrode and the counter electrode are Pt—C, and solid proton conductive membranes are placed between the electrodes and the separator.

Abstract: An aqueous solution of a Na salt of a phenol sulfonic acid polymer as a liquid electrolyte is held in a separator of a liquid electrochemical gas sensor. A sensing electrode and a counter electrode are connected to the separator to detect CO at a range from about ?40 C.° to about 70 C.°.

Abstract: A test signal is applied in parallel with an electrochemical gas sensor for about ten seconds, while an amplifying circuit is turned off. After turning off the test signal, the amplifying circuit is turned on. If the gas sensor outputs an waveform of a predetermined shape in a predetermined period after the turning-on, the gas sensor will be judged to be normal.

Abstract: A proton conductor gas sensor whose durability at high temperature is enhanced by using gel not converted to sol even at high temperature in a water reservoir. Fine particles of silica are gelled by adding water thereto and agitating the mixture under shear force. The thus obtained gel (34) is placed in a water reservoir of proton conductor gas sensor (2) and fed through steam introduction port (30) to MEA (10).

Abstract: A test signal is applied in parallel with an electrochemical gas sensor for about ten seconds, while an amplifying circuit is turned off. After turning off the test signal, the amplifying circuit is turned on. If the gas sensor outputs an waveform of a predetermined shape in a predetermined period after the turning-on, the gas sensor will be judged to be normal.

Abstract: An electrochemical gas sensor is self-diagnosed on the basis of an output waveform that is generated when a power source of said gas sensor is turned on after said power source has been turned off for a short time and an output waveform that is generated when said power source is turned on after said power source has been turned off for a long time. In a normal gas sensor, when the power source is turned on after the power source has been turned off for the short time, a bottom will be generated in the potential of the sensing electrode side, and when the power source is turned on after the power source has been turned off for the long time, a peak will be generated in the potential of the sensing electrode side. A self-diagnosis of the electrochemical gas sensor can be done without pulse power source for self-diagnosis, and the dead time from self-diagnosis until start of detection can be shortened.

Abstract: Water is stored in a metal can, and water vapor is supplied to a separator through an opening in a washer. The separator is an alkali metal salt in a sulfonated synthetic resin membrane, and KOH aqueous solution is used as the electrolyte, and the sensing electrode and the counter electrode are Pt-C, and solid proton conductive membranes are placed between the electrodes and the separator.

Abstract: An electrochemical gas sensor is self-diagnosed on the basis of an output waveform that is generated when a power source of said gas sensor is turned on after said power source has been turned off for a short time and an output waveform that is generated when said power source is turned on after said power source has been turned off for a long time. In a normal gas sensor, when the power source is turned on after the power source has been turned off for the short time, a bottom will be generated in the potential of the sensing electrode side, and when the power source is turned on after the power source has been turned off for the long time, a peak will be generated in the potential of the sensing electrode side. A self-diagnosis of the electrochemical gas sensor can be done without pulse power source for self-diagnosis, and the dead time from self-diagnosis until start of detection can be shortened.

Abstract: A base is provided with a concave and three leads, and the central lead is bent to the side opposite to the concave, and the other leads are bent to the side of the concave. A central electrode of a sensor element is attached to the central lead and the bottom of the concave and a coil serving as both a heater and an electrode is attached to the other leads to support the sensor element on a small base at four points.

Abstract: A central electrode 12 is arranged in a coiled heater electrode 10. They are buried in a SnO2-based inner area 6, and the entirety is covered by a filter 8. The volume of the inner area 6 is set at from 1×10−3 mm3 to 16×10−3 mm3, the total volume of the bead 4 is set at from 15×10−3 mm3 to 70×10−3 mm3, and the ratio of the total volume of the bead 4 to the volume of the inner area 6 is set at from four to twenty to bring the sensor resistance in CO and that in methane closer to each other and increase the selectivity from hydrogen.

Abstract: After sintering of a CO sensor using an SnO2-based metal oxide semiconductor, Ir and Pt are added to the sensor at 5˜500 &mgr;g/g SnO2 each, the weight ratio of Ir and Pt being 5˜1/5. This addition is made by impregnating a mixed aqueous solution of an Ir salt and a Pt salt into the SnO2 sintered body and thermally decomposing these salts. Next, an aqueous solution of thiourea is impregnated into the SnO2 sintered body to add thiourea at 0.01˜10 mg/g SnO2 in reduction to simple S element. The temperature and humidity dependency of the CO sensor is suppressed, the CO concentration dependency of the output is increased, and the sensor resistance is brought to a more convenient range of use.

Abstract: A central electrode 12 is arranged in a coiled heater electrode 10. They are buried in a SnO2-based inner area 6, and the entirety is covered by a filter 8. The volume of the inner area 6 is set at from 1×10−3 mm3 to 16×10−3 mm3, the total volume of the bead 4 is set at from 15×10−3 mm3 to 70×10−3 mm3, and the ratio of the total volume of the bead 4 to the volume of the inner area 6 is set at from 4 to 20 to bring the sensor resistance in CO and that in methane closer to each other and increase the selectivity from hydrogen.

Abstract: A metal oxide semiconductor is subjected to a temperature change, and signals measured at two timings in the course of the temperature change are used to define a two-dimensional topological space. In the topological space, two axis, an axis indicating the concentration of the gas to be detected and an axis corresponding to drift are defined, and the topological space is represented by an oblique coordinate system. The gas concentration is determined from projection of measured data onto the gas concentration axis.

Abstract: A metal oxide semiconductor gas sensor S is connected to a ladder resistance R, and the output voltage is subjected to logarithmic transformation at plural points on a waveform of temperature change byLnR=2-4 V R1/Vc+LnR1 (1)where R indicating the resistance of the metal oxide semiconductor, V R1 the output voltage to the ladder resistance, Vc the detecting voltage, R1 the resistance of the ladder resistance, and Ln natural logarithm, respectively. Standard signals comprising logarithms of resistance values of the metal oxide semiconductor in plural concentrations and at plural points on the waveform are stored in the EEPROM, and these standard signals and logarithms obtained are compared with each other to detect the gas.

Abstract: A film heater and thick-film electrode pads are provided on one main surface of a heat-resistant insulating substrate and are connected by through holes to a metal oxide semiconductor film on the tail surface. Pads are made of a gold alloy such as Au--Pt and connected to leads of Pt--W, etc.

Abstract: An insulating glass film is formed on a heater film, and a gas sensitive film is formed on the glass film. The MgO content in the glass is kept at 0.1 wt % or under to prevent Mg from eluting into absorbed water at low temperatures and segregating on the cathode by the detection voltage.

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.