Abstract: A NOx sensor includes a sensor element equipped with first and second pumping cells to define first and second measurement chambers. The first pumping cell exerts an oxygen pumping action against the first measurement chamber to adjust the oxygen concentration in the gas under measurement within the first measurement chamber to a given level. The second pumping cell exerts an oxygen pumping action against the second measurement chamber to produce a pumping cell current according to the NOx concentration in the gas under measurement. When the moisture content of the gas under measurement changes from 2 vol % to 8 vol %, the NOx sensor allows a variation of NOx concentration detection value based on the pumping cell current in such a manner that the NOx concentration detection value reaches a transient peak value of 20 ppm or smaller and converges to ±5 ppm of a reference value within 5 seconds.

Abstract: A gas sensor 10 for detecting particles in a gas stream has a first electrochemical pump cell 14, which has a measuring chamber 16 in which a first electrode 18 is disposed to pump particles between the first measuring chamber 16 and the gas stream. Furthermore, a second electrochemical pump cell 20 is provided, which has a second measuring chamber 22 in which a second electrode 24 is disposed so as to pump particles. According to the invention, the second measuring chamber 22 is connected to the gas stream via an absorber medium 34 for absorption of the particles to be detected. This makes it possible to absorb the particles to be detected in a first operating mode using the absorber medium 34, and to desorb the absorbed particles in a second operating mode, and to detect the quantity of the desorbed particles. Thus, the gas sensor 10 is able to take even low concentrations into account, and short-term measuring errors do not have such a serious effect.

Abstract: Disclosed herein is a composition for use in a NOx electrode comprising: Tb(1-x)Ln(x)E(1-y)Q(y1)X(y2)Z(y3)O3 wherein Ln is a lanthanoid or a combination of lanthanoids, E is a metal selected from chromium, iron, and a combination thereof, Q is an element selected from magnesium, calcium, strontium, and a combination thereof, X is an element selected from boron, lead, phosphorus, germanium, and a combination thereof, Z is an element selected from barium, silicon, aluminum, and a combination thereof, x is from 0 to about 0.5, y is from about 0.05 to about 0.8, and y1, y2, y3 are independently from 0 to about 0.8, with the proviso that y=y1+y2+y3, and y2+y3 is greater than 0. Also disclosed are a method of making it, electrodes and sensors comprising it, and a method of detecting NOx.

Abstract: The present invention uses a sensor electrode (3) in a nitrogen oxide sensor (10) which includes a nitrate or nitrite of an alkali metal and an oxide of a rare-earth element. The nitrate/nitrite of the alkali metal replaces part of the lattice of the oxide of the rare-earth element, forming a solid solution. The sensor electrode (3) therefore exhibits highly practical features, especially high water-insolubility and capability of nitrogen oxide measurement in a hot and humid atmosphere containing water vapor. Thus, a highly practical nitrogen oxide sensor electrode and nitrogen oxide sensor are provided which are usable in measurement in a hot and humid atmosphere containing water vapor.

Abstract: A method of determining information about a gas sample includes: causing bulk flow of the gas sample in an airstream along at least one flow channel such that all or a significant fraction of the gas sample is consumed on at least one adjacent sensing electrode whereby one or more electrolytic currents are generated, and monitoring at least one electrolytic current so as to determine information about the gas sample.

Abstract: A method of sensor conditioning is proposed for improving signal output stability and differentiation between responses to different gases such as exhaust from combustion processes. DC (or saw tooth) voltage pulses of opposite polarity and equivalent amplitude are applied between sensor electrodes. Pulses are separated by pauses, when charging power supply is disconnected from the sensor and sensor discharge is recorded. Useful information regarding concentration of analyzed gases can be extracted from two measurement methods: 1. Measuring open circuit voltage decay during the pause immediately following voltage pulse. 2. Measuring the discharge current during pauses following voltage (or current) pulses.

Abstract: A mixed potential sensor device and methods for measuring total ammonia (NH3) concentration in a gas is provided. The gas is first partitioned into two streams directed into two sensing chambers. Each gas stream is conditioned by a specific catalyst system. In one chamber, in some instances at a temperature of at least about 600° C., the gas is treated such that almost all of the ammonia is converted to NOx, and a steady state equilibrium concentration of NO to NO2 is established. In the second chamber, the gas is treated with a catalyst at a lower temperature, preferably less than 450° C. such that most of the ammonia is converted to nitrogen (N2) and steam (H2O). Each gas is passed over a sensing electrode in a mixed potential sensor system that is sensitive to NOx. The difference in the readings of the two gas sensors can provide a measurement of total NH3 concentration in the exhaust gas. The catalyst system also functions to oxidize any unburned hydrocarbons such as CH4, CO, etc.

Abstract: Apparatus for detecting the NOx concentration includes a first measurement chamber 20 communicating with the gas under measurement via a diffusion rate defining layer 4d and a second measurement chamber 26 communicating with the first measurement chamber 20 via diffusion limiting layers 6d, 22d. A first pump current IP1 is controlled so that an output of a Vs cell 6 will be equal to the reference voltage VCO for controlling the oxygen concentration in the first measurement chamber 20 to a pre-set low value. A constant voltage is applied across the second pump cell 8 for decomposing the NOx component in the second measurement chamber 26 for pumping out oxygen for detecting the NOx concentration from a second pump current IP2. The sensor temperature is detected from the internal resistance of the Vs cell for controlling the current supplied to the heaters 12, 14. If the temperature of the gas under measurement is changed rapidly, the sensor temperature is changed.

Abstract: An electrochemical gas sensor and methods of operating an electrochemical gas sensor are disclosed. In one embodiment, an electrochemical gas sensor comprising a measuring electrode pair configured to measure a gas species and a pumping electrode pair configured to reduce an amount of an interfering species in a sample in the electrochemical gas sensor is operated by obtaining a measurement of the interfering species at a location spatially adjacent to a measuring electrode of the measuring electrode pair, and adjusting one or more of an operation or an output processing of the electrochemical gas sensor based on the measurement of the interfering species.

Abstract: In a method and with a circuit for operating a nitrogen oxide sensor for determining the nitrogen oxide (NOx) concentration in a gas mixture, in particular in post-treatment of an automotive exhaust, an electric pumping voltage (U_APE,IPE) which induces a pumping current (I_pump) being applied between an internal pump electrode (IPE) and an external pump electrode (APE) of a pumping cell, by which a constant oxygen partial pressure is established in a first test gas space by pumping oxygen in or out, the pumping voltage (U_APE,IPE) being regulated so that a constant voltage value is established at electrodes of a concentration cell, a NOx-sensitive third electrode situated in a second test gas space being operated as the second pumping cell in which a limit pumping current is established, indicating the NOx concentration, in order to minimize the influence of oxygen on the nitrogen oxide signal measured, the pumping current (I_pump) is switched off or reduced in a controlled manner within a measurement time w

Abstract: A method of correcting an output of a NOx sensor including: a first step of obtaining a sensor-variation relational expression based on a relationship between an Ip2/Ip0 value and an output change percentage for a calibration sensor; a second step of obtaining, from the relational expression, an output change percentage ? that corresponds to an Ip2/Ip0 value of a subject NOx sensor; a third step of calculating a pressure correction coefficient ? based on the obtained ?; and a fourth step of performing output correction on the subject NOx sensor by calculating the pumping current Ip2(p0) under a reference pressure based on the pumping current Ip2(p) and a pressure p of the measurement gas which are detected upon measurement of the NOx concentration in the measurement gas.

Abstract: A NOx sensing system having a NOx sensor and a method for determining a NOx concentration utilizing the NOx sensor are provided. The NOx sensor utilizes a second chamber communicating with ambient atmosphere with ambient oxygen for allowing an electrochemical cell to accurately measure an oxygen concentration in a first chamber communicating with an exhaust stream to more accurately control the oxygen concentration in the first chamber, without disassociating NOx therein. The more accurate control of the oxygen concentration in the first chamber, subsequently allows for a more accurate measurement of the NOx in the exhaust system.

Abstract: In a method for operating a measuring probe for measuring a gas concentration in a measuring gas with the aid of a solid electrolyte which conducts oxygen ions and has a measurement cavity for holding the measuring gas, a measuring electrode and an external electrode, a pumping current flowing between the measuring electrode and external electrode transporting oxygen ions from the measuring electrode to the external electrode, the measuring electrode being checked by determining the electrode area effectively available for oxygen diffusion.

Abstract: Electrodes comprising ruthenium oxide nanoparticles are disclosed. The ruthenium oxide nanoparticles are located within the electrode or as a coating thereon. The electrode is especially suited for measuring the presence and/or concentration of nitric oxide in a sample.

Abstract: Exhaust gas sensors and methods for measuring concentrations of NOx and ammonia and temperatures of the sensors are provided. In one exemplary embodiment, an exhaust gas sensor utilizes one zirconia layer and a plurality of alumina layers therein for generating signals indicative of concentrations of NOx and ammonia, and having an impedance indicative of a temperature of the exhaust gas sensor.

Abstract: A gas sensing element has at least a sensor cell consisting of a measured gas side electrode positioned in a measured gas chamber, a reference electrode being operative association with the measured gas side electrode, and a solid electrolytic substrate having surfaces on which the measured gas side electrode and the reference electrode are formed. The measured gas side electrode of the sensor cell contains at least one additive selected from the group consisting of Au, Ag, Cu, and Pb by an amount of 0.01 wt % to 2.0 wt % (external wt %) when an overall amount of the measured gas side electrode is 100 wt %.

Abstract: A concentration detector for detecting the concentration of a particular component in a gas based upon the amount of oxygen formed by the decomposition of the particular component, comprising oxygen-forming means for forming oxygen by decomposing the above particular component, oxygen-discharging means for discharging oxygen from the gas before oxygen is formed by the oxygen-forming means, and oxygen-discharging capability-increasing means for increasing the oxygen-discharging capability of the oxygen-discharging means when the rate of increase of the oxygen concentration in the gas is greater than a predetermined rate before oxygen is formed by the oxygen-forming means.

Abstract: A gas sensor based on solid electrolyte is proposed for measuring a gas component in a gas mixture, having at least one sensitive region, which has a first means for producing a reaction gas from an additional gas component of the gas mixture. A second means is situated in the sensitive region of the gas sensor, using which the residual content of the reaction gas may be determined, after a reaction that takes place between the reaction gas and the gas component to be measured.

Abstract: Disclosed herein are NOx sensors and methods of using the same. In one embodiment, a method for sensing NOx comprises: contacting a first NOx electrode with the gas, contacting a second NOx electrode with the gas, determining a NO2 emf between the first NOX electrode and a first reference electrode, determining a NOx emf between the second NOx electrode and a second reference electrode, and determining a NO2 concentration and a NO concentration using the NO2 emf and the NOx emf. The first electrode can be at a first temperature of greater than or equal to about 700° C., and the second electrode can be at a second temperature of about 500° C. to about 650° C.

Abstract: A noiseless circuit structure of a gas concentration measuring apparatus is provided. The gas concentration measuring apparatus includes a control circuit and a gas sensor including a solid electrolyte body, a cell, and a heater serving to heat the solid electrolyte body up to an activation temperature. The control circuit is designed to cancel or remove electric noises arising from an on-off operation of the heater added to a sensor output.

Abstract: NOx sensor element of oxygen-ion conductive solid electrolyte body 15; flow passage (7, 5, 8, 6) provided within the body for introducing analyte gas; oxygen partial pressure detection cell 3; first oxygen pump cell 1 for controlling oxygen partial pressure of the gas in the flow passage; and nitrogen oxides detection cell 2 for decomposing nitrogen oxides in the gas having a controlled oxygen partial pressure and for causing dissociated oxygen to migrate through the solid electrolyte body (see FIG. 1). Operational amplifier 22b is connected between the nitrogen oxides detection cell 2 and a 12 V battery power source to generate a voltage applied to the nitrogen oxides detection cell 2; and diode 22d connected to a point between the operational amplifier 22b and the nitrogen oxides detection cell. The diode clamps the voltage to an activation voltage higher than the measurement voltage during activation.

Abstract: The embodiments generally relate to porous electrodes for use in solid-state NOx sensors, whereby the electrodes are comprised primarily of ceramic material and electronically conducting material. The electrodes are prepared by impregnating a porous ceramic material with precursors to the electronically conducting material.

Abstract: The present invention is a method and apparatus for measuring the total NOx concentration in a gas stream utilizing the principles of a NOx sensor, i.e., mixed potential sensor. The exhaust gas is first conditioned by a catalyst assembly that converts the various species of nitrogen oxide gases present to a fixed steady state concentration ratio of NO2/NO, where NO2 is approximately 0–10% of the total NOx concentration present in the gas exhaust, thereby enabling the NOx sensor to generate a meaningful and reproducible determination of the concentration of total NOx present in the gas being measured. The catalyst assembly also functions to oxidize any unburned combustibles such as CH4, CO, etc., and remove potential contaminants such as SO2.

Abstract: Disclosed is a gas sensor for controlling a concentration of oxygen and/or measuring NOx by allowing a current to flow through an ion-conductive member for conducting oxygen ion, by the aid of a current supply circuit, wherein the current, which is outputted from the current supply circuit, has a pulse waveform (current signal) having a constant crest value, and the current supply circuit comprises a rectangular wave-generating circuit for controlling a frequency of the current signal on the basis of an electromotive force generated in the ion-conductive member to which the current signal is supplied. Accordingly, it is possible to highly accurately measure the predetermined gas component while scarcely being affected by the electric noise or the like.

Abstract: A detecting electrode comprises a first cermet electrode layer formed directly on a solid electrolyte layer and a second cermet electrode layer formed on the first cermet electrode layer. A ratio between an alloy of Pt—Rh and ZrO2 in the first cermet electrode layer ranges from 20:80 to 50:50 by volume ratio. On the other hand, a ratio between an alloy of Pt—Rh and ZrO2 in the second cermet electrode layer ranges from 60:40 to 50:50 by volume ratio.

Abstract: Electrode having high activity to oxygen gas and low activity to flammable gas is provided. An oxygen pump includes oxide-ion conductive solid electrolyte 2, electrode 8 which is an inactive electrode, and active electrode 10. Electrode 8 is an electrode that includes Ce0.8Sm0.2O2-?. Electrode 8 is disposed on the gas detection chamber 12 side of solid electrolyte 2. Active electrode 10 is disposed on the open space side of solid electrolyte 2. Gas detection chamber 12 is an enclosed space defined by solid electrolyte 2, insulation layers 6, and diffusion control layer 4.

Abstract: A nitrogen oxide sensor system for measuring the amount of nitrogen oxide in a gas. A first electrode is exposed to the gas. An electrolyte is positioned in contact with the first electrode. A second electrode is positioned in contact with the electrolyte. A means for applying a fixed current between the first electrode and the second electrode and monitoring the voltage required to maintain the fixed current provides a measurement of the amount of nitrogen oxide in the gas.

Abstract: A detecting electrode comprises a first cermet electrode layer formed directly on a solid electrolyte layer and a second cermet electrode layer formed on the first cermet electrode layer. The ratio between Pt and Rh in the first cermet electrode layer ranges from 100:0 to 25:75 by weight. The ratio between Pt and Rh in the second cermet electrode layer ranges from 25:75 to 0:100 by weight.

Abstract: An improved engine control system using a NOx sensor is disclosed. In one example, the NOx sensor structure and/or signals are modified to improve distance transmission of NOx sensor output signals so that at least some processing electronics can be relocated remote to the sensor and in an engine control unit, or other such control unit utilizing the NOx sensor signals, and controlling the NOx sensor heaters, if applicable.

Abstract: A gas sensor for determining the concentration of gas components in gas mixtures is used in particular to measure the concentration of nitrogen oxides in exhaust gases of internal combustion engines or in the interiors of motor vehicles. It contains an electrochemical measuring cell which includes a first electrode situated on a solid electrolyte and an additional electrode. The electrode is made of an oxide material containing lanthanum which at least catalytically decomposes nitrogen oxides. The pump current flowing between the electrodes is used as a measure of the nitrogen oxide concentration in the gas mixture.

Abstract: The present invention is a gas component sensor comprising novel electrolyte compositions. The electrolyte compositions in bulk, sintered or thin film embodiments are capable of forming with different-metal sensing and reference electrodes a highly stable gas oxide sensors. The novel electrolyte composition changes electrochemical reactions at the sensing and reference electrodes and the overall reaction of the electrodes and electrolyte. The novel electrolyte compositions have: (1) excellent chemical stability and thermal compatibility as to the electrodes and a preferred ceramic substrate, (2) excellent chemical stability with the environment as to the reference and sensing electrodes, which need not be sealed against the atmosphere to be sensed, (3) effective adherence to the substrate and electrode metals.

Abstract: A method for detecting the concentration of a specific component in gas discharged from an internal combustion engine, which includes detecting the concentration of the specific component under certain driving conditions to determine a zero point, which indicates a zero concentration of the specific component, of the detection output; calibrating the detection output of the gas sensor based on the determined zero point; and detecting the concentration of the specific component in exhaust gas based on the calibrated detection output.

Abstract: A gas concentration detecting apparatus comprises a gas concentration sensor and a gas concentration calculator. The sensor has first to third cells. A gas to be detected is introduced in a chamber and the first cell is responsible for discharging and changing oxygen from and into the chamber. The second cell detects a concentration of a specific gas component of the gas that has passed along the first cell. The third cell detects a concentration of residual oxygen in the gas that remains after discharge of the oxygen through the first cell. The calculator takes in a current acquired from the second cell measured with a voltage applied thereto and calculates the specific gas component concentration based on the current. The calculator includes plural concentration calculating means whose concentration detecting ranges are mutually different in a scale. The specific gas component concentration is calculated every concentration calculating means.

Abstract: A sensor element and a method for determining the concentration of at least one gas component, especially of a nitrogen oxide, in a gas, mixture. For this purpose, the sensor element includes at least one first electrode exposed to the gas component to be analyzed and at least one reference electrode, which are electrically interconnected by a first solid electrolyte. Furthermore, an electric current between the first electrode and a further electrode is measured continuously or in sampling fashion in response to the application, especially the setting, of an electric voltage between first electrode and the reference electrode due to a chemical reaction proceeding at the first electrode, by which the concentration of the gas component to be analyzed in the gas mixture can be determined. During this process, the application or setting of the electric voltage takes place only during recurring time intervals.

Abstract: A gas concentration measuring apparatus which has a gas sensor designed to measure, for example, the concentrations of O2 and HOx contained in exhaust emissions of an automotive engine is provided. The apparatus includes a signal processing circuit which converts a current signal outputted from the gas sensor as a function of the concentration of either of O2 and NOx into a voltage signal. The gas sensor and the signal processing circuit are connected electrically through a conductor. The conductor has a length which is determined as a function of a level of the current signal outputted from the gas sensor. The weaker the level of the current signal is, the shorter the length of the conductor. This minimizes addition of electrical noises to the current signal outputted from the gas sensor.

Abstract: A potentiometric sensor for nitrogen oxide (NOX) measurement based on yttria-stabilized zirconia with a zeolite-modified electrode is presented. A potentiometric sensor of the present invention comprises a tube having an interior and an exterior. A cap member comprising yttria-stabilized zirconia closes one end of the tube. The cap member has an interior surface exposed to the interior of the tube where a first electrode is disposed. The first electrode is then covered with a zeolite layer. A second electrode is disposed on the exterior of the cap member.

Abstract: Apparatus for measuring NOx concentration comprises a NOx sensor element having an oxygen partial-pressure detection cell 3 which detects oxygen concentration of an analyte gas in first measurement chamber 5, first oxygen pump cell 1 across which a current corresponding to oxygen concentration of analyte gas (“a first oxygen pump current”) flows by pumping oxygen from inside to outside of first measurement chamber 1, second measurement chamber 6 into which gas is introduced from first measurement chamber 5 via second diffusion resistance 8, and second oxygen pump cell 2 across which a current corresponding to NOx concentration (“a second oxygen pump current”) flows by transferring oxygen dissociated by decomposition of nitrogen oxide in second measurement chamber 6; and first diagnostic means 30a for diagnosing the apparatus as normally functioning if the second oxygen pump current Ip2 or a predetermined voltage Vp2 applied to second oxygen pump cell 2 is within a predetermined range,

Abstract: A combined oxygen and NOx sensor is provided. Generally, the combined sensor employs a sensor body that includes two different types of electrodes—oxygen-porous electrode layers and dissociative oxygen-porous electrode layers. In accordance with one embodiment of the present invention, the sensor comprises a sensor body, an oxygen content electrical signal output, and a NOx content electrical signal output. The sensor body is disposed in the gas and comprises a plurality of oxygen-porous electrode layers and a plurality of dissociative oxygen-porous electrode layers. The dissociative oxygen-porous electrode layers comprise a material selected to catalyze dissociation of NOx into nitrogen and oxygen.

Abstract: In an improved amperometric gas sensor, the structure, composition, and electrode potential are adjusted so as to prevent or minimize any unwanted reactivity at the counter and/or reference electrode of any analyte or interfering component of the matrix that may cross over thereto. The sensor is preferably structured so that the product of the analyte reaction at a first working electrode can be reconverted to the original analyte at a counter electrode or at a second working electrode and then reacted again at the first working electrode, with such back-and-forth reactions repeating many times, so as to yield an amplification of the analyte signal.

Abstract: The present invention discloses a NOx sensor for accurately detecting the total concentration of nitrogen oxides in a measured gas without being affected by interference gases. The sensor comprises a gas treatment chamber 5 arranged at the prior stage of the gas detection chamber 3, an inorganic porous member 25 loaded in the gas treatment chamber, and a NOx conversion pumping cell 14, 15 and/or an oxygen supplying pumping cell which supplies oxygen into the gas treatment chamber. When the measured gas is introduced in the gas treatment chamber, the interference gases contained in the measured gas are effectively oxidized by the supplied oxygen under the assistance of the catalytic activity of inorganic porous member. The total amount of the nitrogen oxides is measured in the gas detection chamber while NOx in the measured gas are converted into a single component (NO2 or NO) by the NOx conversion pumping cell after the interference gases are oxidized.

Abstract: Method for operating a sensor for determining the concentration of oxidizing gases in gas mixtures, especially of the nitrogen oxide concentration in exhaust gases of internal combustion engines, wherein the sensor includes: at least one chamber (1; 2) mounted in a solid state electrolyte (20), the chamber being connected to the gas mixture via a first diffusion barrier (4); a second chamber (3) arranged in the solid state electrolyte (20) and the chamber having a pregivable constant oxygen partial pressure; on the solid state electrolyte, an oxygen pump electrode (9) subjected to the exhaust gas; a further oxygen pump electrode (7; 8) as well as an NO pump electrode (10) in the at least one chamber (1; 2); and an oxygen reference electrode (6) arranged in the second chamber (3); and at least a voltage is made available at the electrodes and at least a pump current is evaluated as a measurement signal.

Abstract: A novel measurement system for determining total NOX, including NO and NO2 concentration without interference from CO, from a gas sample is presented. The measurement system comprises a gas conduit having an upstream end and a downstream end. The gas conduit carries a gas comprising NOX. Disposed within the gas conduit is a catalytic filter comprising platinum and a zeolite. The gas flowing through the gas conduit interacts with the catalytic filter to form an equilibrium mixture of NO and NO2 from the gas comprising NOX. The measurement system further comprises a sensor element comprising an electrolyte substrate upon which are disposed a sensing potentiometric electrode adapted to contact the equilibrium mixture of NO and NO2 and a reference potentiometric electrode. In practice, there should be a temperature difference between the catalytic filter and the sensor element. Also provided is a method of determining the total NOX content in a gas comprising NOX based on the measurement system.

Abstract: A gas sensor for determining the concentration of gas components in gas mixtures is used in particular to measure the concentration of nitrogen oxides in exhaust gases of internal combustion engines or in the interiors of motor vehicles. It contains an electrochemical measuring cell which includes a first electrode (31) situated on a solid electrolyte and an additional electrode (32). The electrode (31) is made of an oxide material containing lanthanum which at least catalytically decomposes nitrogen oxides. The pump current flowing between the electrodes (31, 32) is used as a measure of the nitrogen oxide concentration in the gas mixture.

Abstract: A method for detecting the concentration of a specific gas (NOx) in an engine exhaust gas using a gas sensor and a process of correcting the gas sensor. According to the correcting process, the amount of moisture in the exhaust gas is estimated, then a a gas concentration detection signal output by the gas sensor on the basis of an estimated amount of moisture is corrected. Finally, the effect of the amount of moisture in the exhaust gas is removed or reduced from the detected value of gas concentration.

Abstract: A low power gas sensor is provided for detecting one or more gases in a gas sample. The gas sensor includes a sensor for sensing a desired gas and a heater for heating the sensor. During operation, a controller provides power to the heater to heat the sensor to an operating temperature during a first period of time. Once at the operating temperature, the controller may read the sensor to determine a measure of the detected gas in the gas sample. Once a measurement is taken, and to conserve power, the controller removes the power to the heater allowing the heater and sensor to cool to at or near the ambient temperature for a second period of time. The second period of time may be longer than the first period of time, and in some cases, substantially longer. In some embodiments, the sensor and heater may be thermally isolated from some or all of the remainder of the gas sensor, such as the sensor substrate.

Abstract: Disclosed herein is a method of improving a chemo/electro-active material by increasing the sensitivity of the material; increasing the stability of an electrical response characteristic of the chemo/electro-active material; or increasing the speed with which a change in an electrical response characteristic of the chemo/electro-active material is detected.

Abstract: A thick-film measurement sensor includes two measurement cells and is used to measure the NOx concentration in the exhaust gas from an internal combustion engine. The 1/&lgr; value of the exhaust gas is determined from an oxygen ion pump current flowing in the first measurement cell, for example, by a characteristic diagram, and, a measurement error, which can be used to correct the measured NOx concentration, is determined from this 1/&lgr; value, for example, by a characteristic curve that has previously been determined in a calibration measurement. The invention is based on the discovery that the measurement error is dependent on the air ratio in the exhaust gas. If this is expressed by the 1/&lgr; value, there is no need for a complex division calculation during the correction.

Abstract: Method and sensor for measuring accurate measurement of NOx concentration in an exhaust gas containing O2,H2O, CO2 and NOx and a NOx gas concentration sensor. A first oxygen pump cell sufficiently pumps out oxygen in a measurement gas such as not to decompose NOx. A pair of electrodes is provided on an inner side and an outer side of a second measurement chamber into which the gas is introduced from a first measurement chamber via a diffusion resistance. A voltage is impressed across the paired electrodes for decomposing NOx in the second measurement chamber to dissociate oxygen which causes the current to flow in a second oxygen ion pump cell. The NOx gas concentration is measured for this current. The voltage impressed across the paired electrodes of the second oxygen ion pump cell is set so as not to dissociate H2O and CO2 present in the second measurement chamber.

Abstract: A NOx sensor for measuring NOx concentration including a main pumping cell and a detecting electrode, the main pumping cell-including an electrode having no decomposing/reducing ability for NOx or a low decomposing/reducing ability for NOx, to be used to control oxygen concentration in a measurement gas to have a predetermined value at which NO is not substantially decomposable, and the detecting electrode having a certain decomposing/reducing ability for NOx or a high decomposing/reducing ability for NOx, to be used so that NOx is decomposed to measure the NOx concentration by measuring an amount of oxygen produced during this process, wherein a cermet electrode composed of a Pt—Rh alloy and a ceramic component is used as the detecting electrode. Accordingly, it is possible to suppress the oxidation of Rh and the reconversion into the metal contained in the detecting electrode, stabilize the impedance, and stabilize the sensitivity to NOx.

Abstract: The present invention discloses a gas sensing device, an oxygen pumping cell, and a gas detection apparatus using the same for detecting lower ranges of gas concentration with high accuracy and stability. An under layer made of oxygen-ion-conductive solid electrolyte was formed between an electrolyte substrate and a sensing electrode, a conversion electrode or a gas treatment electrode. This allows the physical and chemical adhesion between these electrodes and the electrolyte substrate, thereby improving the sensing properties and stability.