Abstract: An oxygen measuring sensor is proposed, having a pump cell (20) with outer and inner pump electrodes (17, 19) disposed on a solid electrolyte (11) which conducts oxygen ions, of which the inner pump electrode (17) is exposed in a diffusion conduit (15) to the gas to be measured. A further electrode (18) of a measuring cell (21) is disposed in the diffusion conduit (15) behind the inner pump electrode (17) in the direction of diffusion, at which a partial oxygen pressure, which lies at least approximately in the vicinity of lambda=1, can be set by means of the pump cell (20), so that the pump cell (20) operates outside of the limiting current range of the current/voltage characteristic curve.

Abstract: The invention is directed to a method for detecting the oxygen content in a gas to be measured. At least one concentration cell operating in accordance with the Nernst principle is provided. The concentration cell includes a measuring electrode communicating with the gas and a solid electrolyte and a reference electrode connected to the measuring electrode through the solid electrolyte. A pump-current pulse is applied between the reference electrode and the measuring electrode and, directly after the end of each pump-current pulse, the current flow between the reference electrode and the measuring electrode is reversed in a pulse-like manner.

Abstract: A sulfur dioxide gas sensor having a high selectivity of SO2 gas, and an operability at a high temperature which comprises: a solid electrolyte having oxygen ion conductivity; a detecting electrode for measuring sulfur dioxide gas, electrically connected to at least a part of a surface of the solid electrolyte and containing glass and either gold or a gold alloy; and a basic electrode for measuring sulfur dioxide gas, electrically connected to at least a part of a surface of the solid electrolyte and containing Pt.

Abstract: A sensing element, in particular for an electrochemical sensor, for determining the oxygen content of gases, includes at least one first electrode exposed to a measured gas and at least one second electrode exposed to a reference gas. A presintered support receiving a sensing device is provided, a porous adhesion layer, also presintered, being arranged between the support and the sensing device.

Abstract: A method and a sensing device of measuring a concentration of a gas component of a measurement gas, which method includes the steps of: introducing the measurement gas containing the gas component, from an external measurement-gas space into a first internal space, under a diffusion resistance; controlling an amount of oxygen in the measurement gas within the first internal space, so as to produce an atmosphere which does not substantially affect measurement of the gas component and which does not convert the gas component; introducing the atmosphere from the first internal space into a second internal space, under a diffusion resistance; and measuring the concentration of the gas component present in the atmosphere in the second internal space.

Abstract: An oxygen sensor is disposed behind an exhaust gas purifying catalyst for an internal combustion engine and which suppresses the influence of unburnt hydrocarbon on the output voltage. A sensor element 1 is provided with a detection electrode 4 on the outer face of a zirconia ceramic body 2, a reference electrode 3 on the inner face of the ceramic body 2 and a spinel protective layer 5 on the outer surface of the detection electrode 4. The tip end of the sensor element 1 is covered with a protective cover 10 which is provided with an outer partition wall 11 having through holes 11a and an inner partition wall 12 having through holes 12a. In a case where the pressure difference between the inside and outside of the protective cover 10 is &Dgr;P(atm) when the atmospheric air with a volume flow rate Q(L/min) is passed into the protective cover 10 from the outside, the ratio &Dgr;P/Q2 is 3.2×10−5 (atm·min2·L−2).

Abstract: A modified universal exhaust gas oxygen sensor, referred to herein as a CEGA sensor, is provided which can be used to measure the concentration of a variety of components of a gaseous fuel emission including CO, CO2, O2, H2, and H2O. The CEGA sensor employs at least one additional electrode on a ceramic substrate which possess a different catalytic activity relative to the electrodes that normally found on a UEGO sensor. The ceramic substrate may be made of any suitable ceramic and is preferably made of zirconia. The difference in catalytic activity between the additional electrode(s) and the electrodes native to the UEGO sensor create an oxygen gradient which enables a measure of combustion completeness to be calculated. In combination with an air/fuel ratio measured by the sensor, the concentrations of different components in the emission can be calculated.

Abstract: A method for producing a NOx sensor comprises the steps of forming electrodes on ceramic green sheets, and stacking and integrating the ceramic green sheets into one unit followed by sintering to prepare a substrate, wherein an oxygen concentration is controlled to be not more than 0.5% in a sintering atmosphere after removal of a binder in the step of sintering the substrate. Specifically, the sintering is performed in an atmospheric atmosphere in Interval 1 in which the temperature in a furnace is changed from room temperature to about 1000.degree. C., and the sintering is performed in a nitrogen atmosphere (oxygen concentration in the atmosphere in the furnace is controlled to be about 400 ppm) in Interval 2 in which the temperature is changed from 1000.degree. C. to a maximum temperature followed by spontaneous radiational cooling.

Abstract: First and second solid electrolyte bodies are opposed to one another to form a reference gas chamber therebetween. A measurement cell for detecting an air fuel ratio in measurement gas is provided on the first solid electrolyte body with a measurement electrode exposed to the measurement gas and a reference electrode exposed to the reference gas chamber. An oxygen pump cell is provided on the second solid electrolyte body with a first pump electrode exposed to the measurement gas and a second pump electrode exposed to the reference gas chamber. When a voltage is applied to the first and second oxygen pump cell, the oxygen gas is introduced from the measurement gas into the reference gas chamber.

Abstract: A gas sensor 1 including a first processing space 9; a first gas passage 11; a second processing space 10; a second gas passage 13; an oxygen concentration detection element 4; a first oxygen pumping element 3 adapted to reduce the oxygen concentration of exhaust gas introduced into the first processing space 9 within a range such that a water vapor contained in the measurement gas is not substantially decomposed; an oxygen catalyst section 16; and a combustible gas component concentration information generation/output section 5. Also disclosed is a gas sensor system including the above gas sensor and first oxygen pumping operation control means for adjusting the oxygen concentration of the measurement gas introduced into the first processing space within a range such that water vapor contained in the measuring gas is not substantially decomposed.

Abstract: A modified universal exhaust gas oxygen sensor, referred to herein as a CEGA sensor, is provided which can be used to measure the concentration of a variety of components of a gaseous fuel emission including CO, CO.sub.2, O.sub.2, H.sub.2, and H.sub.2 O. The CEGA sensor employs at least one additional electrode on a ceramic substrate which possess a different catalytic activity relative to the electrodes that normally found on a UEGO sensor. The ceramic substrate may be made of any suitable ceramic and is preferably made of zirconia. The difference in catalytic activity between the additional electrode(s) and the electrodes native to the UEGO sensor create an oxygen gradient which enables a measure of combustion completeness to be calculated. In combination with an air/fuel ratio measured by the sensor, the concentrations of different components in the emission can be calculated.

Abstract: An air-fuel ratio sensor system is diagnosed for the presence/absence of an abnormality on the basis of a reference voltage appearing at one end of a current detecting resistor and a detection voltage appearing at the other end of the current detecting resistor for detecting a current output by an air-fuel ratio sensor. If the reference voltage is outside a normal range and higher than the detection voltage, the air-fuel ratio sensor system is determined to be in a rich abnormality. If the reference voltage Vafon is outside the normal range and lower than the detection voltage, the air-fuel ratio sensor system is determined to be in a lean abnormality. If the reference voltage is within the normal range and a state of the detection voltage being close to a power supply voltage has been continuing for a predetermined period of time, the air-fuel ratio sensor system is determined to be in a circuit-shorting.

Abstract: The present invention provides an apparatus for measuring the concentration of a constituent to be detected in exhaust gas, which apparatus is capable of detecting with a high accuracy the concentration of the constituent to be detected in exhaust gas even though oxygen concentration in the exhaust gas varies. In an exhaust gas sensor 1 for use in the measuring apparatus, exhaust gas is introduced into spaces 15, 16 on both sides of an oxygen concentration cell element 4, and the oxidation catalyst activities of first to third electrodes 11 to 13 are adjusted so that there occurs a difference between the space 15 and the space 16 in consumption of the constituent to be detected, which consumption is caused by the oxidation of the constituent. Thus a concentration cell electromotive force is generated in the oxygen concentration cell element 4, and an oxygen pump element 3 pumps oxygen into or out of the space 15 so that the electromotive force is held at an target value EC not more than 10 mV.

Abstract: A constant current Iconst is applied to an electromotive force cell which is interposed between a gap (measurement chamber) of a fixed atmosphere and an oxygen reference chamber of a constant oxygen content, for measurement of a resistance value of the electromotive force cell, whereby the resistance value can be measured accurately irrespective of an oxygen content in an atmosphere to be measured by an oxygen sensor element or cell unit. The resistance value of the electromotive force cell is measured at a predetermined timing T2 after application of a current is started, so that a measure resistance value is free of a variation of a resistance value due to deterioration of porous electrodes of an electromotive force cell, such a variation being included in the measured resistance value in case the measurement is done by using an AC current, and therefore accurate measurement can be attained.

Abstract: Disclosed is a gas sensor comprising a main pumping cell for pumping-processing oxygen in a first chamber; an auxiliary pumping cell for pumping-processing oxygen in a second chamber; and a measuring pumping cell for pumping-processing oxygen in a measurement gas introduced through a third diffusion rate-determining section; wherein a NOx component contained in the measurement gas is measured on the basis of a pumping current flowing through the measuring pumping cell. The gas sensor further comprises a heater for heating at least the main pumping cell, the auxiliary pumping cell, and the measuring pumping cell to predetermined temperatures; an impedance-detecting circuit for detecting an impedance between an inner pumping electrode and an auxiliary pumping electrode; and a self-diagnosis unit for comparing an impedance value detected by the impedance-detecting circuit with a prescribed value to decide whether or not any trouble occurs, on the basis of a result of comparison.

Abstract: A method of detecting a deteriorated condition of a wide range air-fuel ratio sensor is provided. Firstly, a current is applied to an electromotive force cell to detect a voltage Vs0 across electrodes on opposite side surfaces of the cell. Application of the current is suspended, and a voltage drop Vsd1 across the electrodes is detected after lapse of a time ranging from 10 .mu.s to 1 ms after the application of the current is suspended. Based on the voltage drop Vsd1 is detected a first resistance value Rvs1 equated to the temperature of the electromotive force cell. Further, after lapse of a time ranging from 10 ms to 50 ms after the application of the current to the electromotive force cell is suspended, a voltage drop Vsd2 across the electrodes of the electromotive force cell is detected. Based on the voltage drop Vsd2 is detected a second resistance value Rvs2 equated to an internal resistance of the electromotive force cell including a resistance component resulting from deterioration.

Abstract: Disclosed are a gas sensor and a gas concentration controller each comprising a comparative amplifier for comparing a reference voltage with a terminal voltage between a reference electrode and an inner pumping electrode to obtain a difference therebetween, and amplifying the difference with a predetermined gain to make an output. Wiring connection is arranged so that the output voltage from the comparative amplifier is applied, as a pumping voltage to an oxygen pump, between the electrode and an outer pumping electrode. A resistor for detecting a pumping current is inserted and connected between an output terminal of the comparative amplifier and the electrode of the oxygen pump. A short circuit is formed between both ends of the resistor by using a capacitor. One electrode of the capacitor is connected to a non-inverting terminal of a differential amplifier, and the other electrode is connected to an inverting terminal of the differential amplifier.

Abstract: Disclosed is a gas sensor comprising a main pumping cell for pumping-processing oxygen contained in a measurement gas introduced into a first chamber, an auxiliary pumping cell for pumping-processing oxygen contained in the measurement gas introduced into a second chamber, a measuring pumping cell for pumping-processing oxygen in the measurement gas introduced via a third diffusion rate-determining section, an ammeter for detecting a pumping current generated depending on an amount of oxygen pumping-processed by the measuring pumping cell, a heater for heating at least the main pumping cell, the auxiliary pumping cell, and the measuring pumping cell to a predetermined temperature, an impedance-detecting circuit for detecting an impedance between an inner pumping electrode and an auxiliary pumping electrode, and a heater control circuit for controlling electric power application to the heater on the basis of a value of the impedance detected by the impedance-detecting circuit.

Abstract: A method and a sensing device of measuring a concentration of a gas component of a measurement gas, which method includes the steps of: introducing the measurement gas containing the gas component, from an external measurement-gas space into a first internal space, under a diffusion resistance; controlling an amount of oxygen in the measurement gas within the first internal space, so as to produce an atmosphere which does not substantially affect measurement of the gas component and which does not convert the gas component; introducing the atmosphere from the first internal space into a second internal space, under a diffusion resistance; and measuring the concentration of the gas component present in the atmosphere in the second internal space.

Abstract: An air-to-fuel (A/F) ratio sensor includes an insulation layer, two solid electrolyte layers made of a porous composite ceramic formed at both sides of the insulation layer, each solid electrolyte layer having an internal electrode layer on its boundary surface with the insulation layer and an external electrode layer on its other surface, and a diffusion barrier layer made of a porous composite ceramic, covering one of the external electrode layers. The A/F ratio sensor provides a linear A/F ratio signal by controlling only a pumping current for a reference partial pressure of oxygen. Thus, the A/F ratio sensor operates by a simpler driving principle, thereby simplifying the driving circuit thereof.

Abstract: A small-sized inexpensive nitrogen oxide concentration sensor capable of measuring the concentration of the nitrogen oxide in a measuring gas to a high accuracy. A first oxygen pumping cell, an oxygen concentration measuring cell and a second oxygen pumping cell are formed in different solid electrolyte layers of zirconia and electrodes of oxygen concentration measuring cell are isolated from electrodes of the oxygen pumping cells by insulating film.

Abstract: A gas sensor using oxygen-ion-conductive solid electrolyte layers measures a concentration of a constituent gas such as NOx in a gas mixture such as an exhaust gas mixture of an internal combustion engine. The gas sensor includes a pair of oxygen pumping cells and a sensor cell. Before the constituent gas concentration is measured by the sensor cell, oxygen gas contained in the gas mixture has to be purged because the oxygen gas adversely affects the measurement of the constituent gas concentration. Two pumping cells disposed to face a chamber, into which the gas mixture is introduced, pump out the oxygen gas contained in the gas mixture so that the oxygen concentration is reduced substantially zero. Then, the gas mixture is diffused to the sensor cell where the constituent gas concentration is measured without the adverse influence of the oxygen gas. A marginal ion current which is proportional to the constituent gas concentration is measured by the sensor cell with a high accuracy and sensitivity.

Abstract: A gas sensor comprises a main pumping cell for pumping-processing oxygen contained in a first chamber, a feedback control system for comparing a partial pressure of oxygen in the first chamber with a first reference value to control the main pumping cell so that the partial pressure of oxygen has a predetermined value at which NO is not decomposable, an auxiliary pumping cell for pumping-processing oxygen in the second chamber, and a measuring pumping cell for pumping-processing oxygen produced by decomposition of NOx.

Abstract: Disclosed is a gas sensor comprising a first internal space for making communication with the external space via a first diffusion rate-determining section, a first electrochemical pumping cell for controlling the oxygen concentration in the atmosphere in the first internal space to have a predetermined value, a second internal space for making communication with the first internal space via a second diffusion rate-determining section, a second electrochemical pumping cell for finely adjusting the oxygen concentration in the atmosphere in the second internal space to have a predetermined value, a third internal space for making communication with the second internal space via a third diffusion rate-determining section, a third electrochemical pumping cell for pumping out oxygen produced by reduction or decomposition of a component having bound oxygen in the measurement gas in the third internal space, and an ammeter Ip for detecting a pumping current which is allowed to flow in accordance with the pumping ope

Abstract: A method for measuring nitrogen oxide (NOx) in a gas by decomposing NOx in the gas and measuring an amount of oxygen generated by the decomposition includes: introducing the gas to a first inner space under a first diffusion resistance and connected with an external space, controlling an oxygen partial pressure in an atmosphere in the first inner space to be a predetermined low value at which NO is not decomposed substantially by a main pump means, introducing a controlled atmosphere of the first inner space into a second inner space which is connected with the first inner space and which is under a second diffusion resistance, and converting the atmosphere into an electric signal corresponding to the quantity of oxygen generated by decomposition or reduction of NOx contained in the atmosphere by an electric signal conversion means.

Abstract: A system is constructed such that a voltage between an inner pumping electrode and a reference electrode is measured to determine a difference between a measured voltage and a reference voltage so that a pumping voltage is controlled by using the differential voltage. Specifically, a comparative amplifier is provided for comparing the reference voltage with the terminal voltage between the reference electrode and the inner pumping electrode, and amplifying the difference therebetween with a predetermined gain to make an output. The system is wired and connected such that the output voltage (differential voltage) from the comparative amplifier is applied, as the pumping voltage supplied to an oxygen pump, between the inner pumping electrode and an outer pumping electrode. The inner pumping electrode is grounded. Accordingly, for example, when the oxygen pump is used, it is possible to effectively avoid the oscillation phenomenon in the feedback control system for the control voltage for the oxygen pump.

Abstract: Disclosed is a method for controlling a gas sensor comprising the steps of pumping-processing oxygen contained in a measurement gas introduced from external space into a first chamber by using a main pumping cell so that a partial pressure of oxygen in the first chamber is controlled to have a predetermined value at which a predetermined gas component as a measurement objective is not decomposable; decomposing the predetermined gas component contained in the measurement gas in a second chamber by the aid of a catalytic action and/or electrolysis by using a detecting pumping cell to pumping-process oxygen produced during the decomposition; and measuring the predetermined gas component contained in the measurement gas on the basis of a pumping current which flows during the pumping process; wherein the oxygen to be pumped out by the detecting pumping cell is pumped out toward an inner pumping electrode which is fixed to have a base electric potential (ground electric potential), of the main pumping cell.

Abstract: There are proposed an air/fuel ratio sensor which can detect a wide range of an air/fuel ratio and provides a simple structure, a superior mechanical strength or durability and a reduced manufacture cost, and a method of detecting the air/fuel ratio using the air/fuel ratio sensor. An air/fuel ratio sensor 1 is formed of a detecting portion 2 and a heater portion 3 laminated via a porous body 16. In the detecting portion 2, on an inner face of a plate-like solid electrolytic body 5, a reference electrode 7 is provided for controlling an oxygen gas diffusion rate, and on an outer face of the solid electrolytic body 5, a measurement electrode 6 is provided. A surface of the measurement electrode 6, on which the diffusion rate is not controlled, is covered with a protective layer 14 having an ventilation property to a degree to which the diffusion rate is not substantially controlled. A lead portion 7b of the reference electrode 7 is a porous layer which substantially controls the diffusion rate.

Abstract: A sensor cleaning method and a detection apparatus enabling easy and correct measurement for an uninterrupted prolonged time duration of the gas concentration.The method is based on the value of a limiting current generated on applying a dc voltage across a pair of positive and negative electrodes of a sensor in which the electrodes are formed of a porous material and arranged in intimate contact with the surface of a solid electrolyte substrate exhibiting oxygen ion conductivity and in which pores of the negative electrode are used simultaneously as gas diffusion limiting holes for limiting the amount of diffusion of the gas for measurement. If the limiting current characteristics of sensor versus applied voltage are deteriorated, a voltage opposite to that used during measurement is applied for restoring the characteristics to a normal value.

Abstract: Disclosed is an oxide sensor in which O.sub.2 contained in a measurement gas introduced into a first chamber through a first diffusion rate-determining section is removed by the aid of a pumping voltage applied between pumping electrodes, and then the measurement gas is introduced into a second chamber through a second diffusion rate-determining section to remove excessive O.sub.2 by the aid of auxiliary pumping electrodes. A detecting electrode is arranged to satisfy d.gtoreq.t provided that d represents a distance from an end of the auxiliary pumping electrodes on the side of the second diffusion rate-determining section to an end of the detecting electrode on the side of the second diffusion rate-determining section, and t represents a height of the second chamber. A predetermined pumping voltage is applied to the detecting electrode to decompose oxides contained in the measurement gas by the aid of the detecting electrode or a catalyst.

Abstract: An A/F sensor outputs a linear air-fuel ratio detection signal proportional to the oxygen concentration in an exhaust gas from an engine upon application of a voltage. A computer controls the applied-voltage in a stoichiometric control region, a lean burn control region, an atmosphere detection region and a rich control region to have a fixed value such that the change rate of the applied-voltage is reduced to be less than that in other regions. In addition, when changing the voltage applied to the A/F sensor, the computer variably sets the voltage change speed sequentially. Thus, the influence of the capacitive characteristic of the A/F sensor is eliminated.

Abstract: In accordance with the present invention, there is provided an exhaust gas sensor which comprises an oxygen pump cell made of solid electrolyte having an oxygen ion conductivity, an oxygen sensor cell made of solid electrolyte having an oxygen ion conductivity and disposed in opposition to the pump cell in such a manner as to define therebetween a detection space, and a semiconductor detection element made of oxide semiconductor and disposed in the detection space for detecting a predetermined detected substance in the exhaust gas introduced to the detection space. The concentration of oxygen in the detection space is regulated so as to be included within a predetermined range through control of charge or discharge of oxygen into or from the detection space by means of the oxygen pump cell on the basis of the concentration of oxygen in the exhaust gas, which is detected by the oxygen sensor cell.

Abstract: An A/F sensor generates a current signal corresponding to an air-fuel ratio in response to a voltage applied by a bias control circuit. After a sensor current is received as a voltage signal via a voltage follower, it is outputted to an A/D converter having a predetermined input voltage range, 0 to 5V. A sensor current detection circuit has a plurality of current detection resistors. In order to variably set the resistance value by the sensor current detection circuit, a switch circuit is switched in accordance with the sensor current depending on whether the A/F value to be detected is in the zone near the stoichiometric ratio or in other air-fuel ratio zones.

Abstract: Disclosed is a gas sensor comprising a main pumping cell including a solid electrolyte layer contacting with an external space, and an inner pumping electrode and an outer pumping electrode formed on inner and outer surfaces of the solid electrolyte layer, for pumping-processing oxygen contained in a measurement gas introduced from the external space on the basis of a control voltage applied between the electrodes; a feedback control system for adjusting the control voltage to give a predetermined level of a voltage between the inner pumping electrode and a reference electrode disposed at a reference gas-introducing space; and a heater for heating at least the main pumping cell to a predetermined temperature; wherein the outer pumping electrode is connected to a negative side lead wire of the heater.

Abstract: A method of detecting an activated condition of a wide range air-fuel ratio sensor is provided. With this method, application of a current to a heater is started idiately after an engine is started (S00). Then, a current Icp for pumping is passed through an electromotive force cell (S10). A lapse of a predetermined time Tin is waited for (S18). After a lapse of time Tin, a voltage Vs across both electrodes of the electromotive force cell is detected (S20) and labeled as Vs0 (S22). Then, application of Icp is suspended (S30) and a routine is held on standby until a time of 25 ms elapses (S35). At the point of time when the time of 25 ms has elapsed, the voltage across the electrodes on the opposite sides of the electromotive force cell is detected (S40) and labeled as Vs1 (S45). A resistance value Rs1 is calculated from Vs0, Vs1 and Icp (S50).

Abstract: A wide range air to fuel (A/F) ratio sensor having a solid electrolyte plate, a measurement electrode and a first pumping electrode both formed at one surface of the solid electrolyte plate, the measurement electrode serving as both an oxygen pumping electrode and a sensing electrode, and a second pumping electrode and a sensing reference electrode both formed at another surface of the solid electrolyte plate, the sensing reference electrode being supplied with oxygen from the first pumping electrode and thereby serving as an oxygen reference electrode. The wide range A/F ratio sensor can be driven by a reference voltage variation method which adds a surplus voltage to a reference voltage.

Abstract: Disclosed is an oxide sensor in which a measuring electrode is arranged at a distance d to satisfy -3t.ltoreq.d.ltoreq.3t for a downstream end of an inner pumping electrode for a first chamber, i.e., the end located on a side of a second diffusion rate-determining section, provided that d represents a distance between the measuring electrode and the downstream end in a positive direction directed from the first chamber to a second chamber, and t represents a height of the first chamber. A partial pressure of oxygen in the first chamber is measured by using the measuring electrode. A main pumping cell is subjected to feedback control on the basis of a measured value so that the partial pressure of oxygen in the first chamber is controlled. After that, a measurement gas is introduced into the second chamber. Oxides contained in the measurement gas are decomposed by the aid of a detecting electrode or a catalyst.

Abstract: A method and a sensing device of measuring a concentration of a gas component of a measurement gas, which method includes the steps of: introducing the measurement gas containing the gas component, from an external measurement-gas space into a first internal space, under a diffusion resistance; controlling an amount of oxygen in the measurement gas within the first internal space, so as to produce an atmosphere which does not substantially affect measurement of the gas component and which does not convert the gas component; introducing the atmosphere from the first internal space into a second internal space, under a diffusion resistance; and measuring the concentration of the gas component present in the atmosphere in the second internal space.

Abstract: An air-fuel ratio sensing element comprises a cup-shaped solid electrolyte with one end opened and the other end closed, an external electrode provided on an outer wall surface of the solid electrolyte so as to be exposed to measured gas, and an internal electrode provided on an inner wall surface of the solid electrolyte in a confronting relationship to the external electrode. A first insulating layer, made of a gas-permeable and nonconductive porous material, is provided on the external electrode at least in a region used for detecting of an air-fuel ratio. A second insulating layer is provided outside the first insulating layer and, a heater layer as provided between the first insulating layer and the second insulating layer.

Abstract: An A/F sensor is driven by a voltage applied thereto at a command issued by a microprocessor, outputting an A/F detection signal which is linearly proportional to the concentration of oxygen. The microprocessor controls the voltage applied to the A/F sensor to bring a current flowing through the A/F sensor to a predetermined value in a zone outside a predetermined air-fuel ratio detection zone. In this outside zone, the applied voltage is controlled in accordance with a characteristic different from a positive characteristic in a normal positive characteristic in a voltage-current relation. That is, in a rich zone outside the air-fuel ratio detection zone, the applied voltage is controlled so as to make the applied voltage approach a maximum value of the electromotive force of the A/F sensor. In a lean zone outside the air-fuel ratio detection zone, on the other hand, the applied voltage is controlled so as to make the applied voltage approach a minimum value of the electromotive force of the A/F sensor.

Abstract: A gas sensor for measuring a quantity of specific component in a measuring gas includes a main pump means which has an electrochemical pump cell. The electrochemical pump cell includes a solid electrolyte partition exposed to external space, an inner pump electrode and an outer pump electrode formed on the inner surface and outer surface of the solid electrolyte partition, respectively. The main pump means treats oxygen contained in the measuring gas introduced from the outer space by pumping processing on the basis of a control voltage applied between the inner pump electrode and the outer pump electrode. An RLC element which has a specific electric characteristic value corresponding to a characteristic value of the electrochemical pump cell is connected in parallel with the electrochemical pump cell.

Abstract: An oxygen concentration-detecting device for an internal combustion engine includes an oxygen concentration sensor arranged in the exhaust system of the engine, for detecting concentration of oxygen present in exhaust gases emitted from the engine. Energization of a heater for heating the oxygen concentration sensor is started when the ignition switch is turned on. The energization of the heater is stopped after a predetermined time period has elapsed after the turning-on of the ignition switch.

Abstract: Disclosed is a gas sensor comprising inner pumping electrodes arranged on upper and lower surfaces and both side surfaces in a first chamber so that O.sub.2 contained in a measurement gas introduced through a first diffusion rate-determining section is effectively removed by the aid of a pumping voltage applied between the inner pumping electrodes and an outer pumping electrode. After the removal of O.sub.2, the measurement gas is introduced into a second chamber through a second diffusion rate-determining section so that oxides contained in the measurement gas are decomposed by the aid of a detecting electrode, or O.sub.2 is bound to inflammable gases contained in the measurement gas. An amount of oxygen moved or transported in accordance therewith is measured to determine the concentration of the oxides or the inflammable gases. Accordingly, the oxygen contained in the measurement gas can be effectively controlled, making it possible to highly accurately measure the oxides or the inflammable gases.

Abstract: An air/fuel ratio sensor is controlled such that the oxygen concentration of the measurement gas can be detected from a pump current substantially instantaneously after a heater turns on. In the air/fuel ratio sensor an oxygen pumping cell and an oxygen concentration measuring cell are each formed of a solid electrolytic layer interposed between a pair of porous electrodes. One of the electrodes of each cell defines a measurement gas chamber in which the diffusion of the measurement gas is controlled. After a micro current is supplied to the other electrode of the oxygen concentration measuring cell for a predetermined period of time, thereby forming an internal reference oxygen source, the supply of the micro current is stopped and at the same time a pump current in the oxygen pumping cell starts to be controlled until the interelectrode voltage of the oxygen concentration measuring cell reaches a target voltage. After the air/fuel ratio sensor is activated, the supply of the micro current is restarted.

Abstract: An electrochemical measuring sensor having a solid electrolyte, a first electrode exposed to a gas to be measured and a second electrode exposed to a reference gas, with the electrodes preferably being arranged on opposite sides of the solid electrolyte. At least one of the electrodes (16, 20) is provided with a contouring (24) on its side (22) that is exposed to the gas to be measured or to the reference gas, with the contouring being a trench-shaped groove (26) embossed into the surface of the electrode such that the electrode is pressed into the adjacent solid electrolyte in the region of the groove. According to the method, the embossing is done while the electrode and the solid electrolyte are in the non-sintered state, and the sensor is subsequently sintered.

Abstract: An electrochemical measuring sensor for selectively determining nitrogen oxides in a gas mixture including oxygen and nitrogen oxides, includes a solid electrolyte layer; a cover layer; and a diffusion channel which is defined between the solid electrolyte layer and the cover layer, and through which the gas mixture diffuses in a diffusion direction. The solid electrolyte layer has provided on a surface thereof a first cathode and a second cathode disposed one after the other in the diffusion direction of the gas mixture within the diffusion channel and exposed to the gas mixture in the order recited, and has provided on an opposite surface thereof at least one anode. The diffusion channel forms a diffusion barrier for the second cathode. The first and second cathodes and the at least one anode are gas permeable and consist of one of a precious metal or a precious metal alloy. The first cathode is provided with a coating which completely covers same, which is impermeable to nitrogen oxides (NO.sub.

Abstract: An apparatus for measuring a combustible gas component of a subject gas in an external subject gas space, including a first processing zone communicating with the subject gas space, a second processing zone communicating with the first processing zone, and a first and a second pumping cell exposed to the first and second processing zones, respectively, each cell including an oxygen ion conductive solid electrolyte layer and a pair of electrodes one of which is exposed to the first or second processing zone, wherein the first pumping cell pumps oxygen out of the first processing zone to control oxygen partial pressure in the first processing zone at a value at which the combustible gas component cannot be burned, while the second pumping cell pumps oxygen into the second processing zone to thereby burn the combustible gas component in the second processing zone, and the concentration of the combustible gas component is determined based on a current flowing or a voltage between the electrodes of the second pump

Abstract: A gas sensor which can be used for measuring a low concentration repeatedly, which has a quick response and which can be used for a long time with high stability is provided. The gas sensor comprises a solid electrolyte, a detecting electrode provided in contact with one of the surfaces of the solid electrolyte and exposed to a gas to be detected, a counter electrode, provided in contact with the other surface of the solid electrolyte, and lead wires to place an electric voltage across both electrodes or to take out electric signals, wherein an inactive substance which is hard to form a reaction product with the gas to be detected is used as a material to constitute both electrodes.

Abstract: A method and a sensing device of measuring a concentration of a gas component of a measurement gas, which method includes the steps of: introducing the measurement gas containing the gas component, from an external measurement-gas space into a first internal space, under a diffusion resistance; controlling an amount of oxygen in the measurement gas within the first internal space, so as to produce an atmosphere which does not substantially affect measurement of the gas component and which does not convert the gas component; introducing the atmosphere from the first internal space into a second internal space, under a diffusion resistance; and measuring the concentration of the gas component present in the atmosphere in the second internal space.

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.