Abstract: The present invention discloses a trace oxygen measuring apparatus comprising a trace oxygen generating unit capable of generating oxygen in an arbitrary amount within a range of from 1 to 2 ppm, a concentration detecting cell configured so as to ensure followup of Nernst's formula, an opposite pump electrode provided in a special air duct, and a concentration detecting cell and a pump cell electrode independently provided; and a trace oxygen generating apparatus used such trace oxygen measuring apparatus.

Abstract: A method of evaluating properties of an oxygen sensor used for detecting air-fuel ratio of exhaust gas from internal combustion engine comprises steps of preparing a burnt gas having a predetermined excess air ratio, supplying additional oxidation gas and/or reduction gas into the burnt gas, and detecting an output from the sensor exposed to the mixed gas flow. The supply amount of the additional gas is increased and decreased with a frequency of at least 10 Hz, and a ratio of a supply increasing period to a supply decreasing period is changed to change the supply amount of the additional gas, so that an excess air ratio .lambda. can be controlled similarly to exhaust gas from an actual engine.

Abstract: An electrochemical device having an oxygen-ion conductive solid electrolyte body, a plurality of electrodes formed on the solid electrolyte body, an electrically insulating ceramic layer formed on the solid electrolyte body, a heater disposed such that the heater is electrically insulated by the ceramic layer from the solid electrolyte body, and a dc power source electrically connected to the heater for energizing the heater. At least one of the electrodes is electrically connected to a low-potential terminal of the dc power source. A voltage source is connected in a line between the above-indicated at least one electrode and the low-potential terminal of the dc power source, so that a potential of each of the at least one electrode with respect to a potential V1 at a point of connection of the above-indicated line to the low-potential terminal of the dc power source is maintained at a positive value which satisfies a formula, V1.ltoreq.

Abstract: An NOx sensor having an electrochemical cell having a solid electrolyte body and a first and a second electrode, a portion that permits restricted communication of the first electrode with an external measurement gas space, a catalyst disposed adjacent the first electrode for decomposing NOx, a device for applying a current between the first and second electrodes, a current measuring device for detecting a current flowing between the first and second electrodes, an oxygen partial pressure measuring device for detecting an oxygen partial pressure of the atmosphere surrounding the first electrode, and a control device for calculating the concentration of NOx contained in the measurement gas in the external space, based on a first and a second current value.

Abstract: A heater-built-in sensor for detecting a component in a measurement gas, including an electrochemical cell having a solid electrolyte body, and a pair of electrodes formed on the solid electrolyte body, a heater for heating at least a detecting portion of the cell which includes the measuring electrode, and a protective covering device disposed around the detecting portion. The covering device includes a gas-inlet portion for introducing the measurement gas to the measuring electrode, and a thermally insulating portion for preventing dissipation of a heat generated by the heater. The thermally insulating portion, which is separated from the gas-inlet portion, is adapted to surround the detecting portion so as to prevent the measurement gas from flowing to and from any parts of the detecting portion, except a part at which the measuring electrode is located.

Abstract: An electrochemical device having a sensing cell and a pumping cell. The sensing cell includes: a first planar solid electrolyte body; a first and a second porous electrode disposed on the first planar solid electrolyte body, the second electrode being exposed to a reference gas which has a predetermined oxygen partial pressure; and a diffusion resistance member which has a predetermined diffusion resistance to a measurement gas and covers the first electrode. An electric current is applied between the first and second electrodes, such that the electric current flows from the first electrode to the second electrode to induce an electrode reaction for controlling an atmosphere adjacent to the first electrode. The pumping cell includes: a second planar solid electrolyte body; a third and a fourth electrode of a porous structure disposed on the second planar solid electrolyte body.

Abstract: A method of effecting determination whether a measurement gas is a rich-burned exhaust gas or a lean-burned exhaust gas, by using an oxygen concentration sensor which includes at least one solid electrolyte member of an oxygen-ion conductive material, and at least two electrodes, one electrode being an electrode which is exposed to the measurement gas through diffusion-resistance means, the steps of: applying an electric current to the electrode exposed to the measurement gas through the diffusion-resistance means, such that the electric current flows in one of opposite directions depending upon whether the measurement gas is a rich-burned exhaust gas or a lean-burned exhaust gas, so as to maintain an atmosphere adjacent to the electrode exposed to the measurement gas through the diffusion-resistance means to be stoichiometric; and detecting one of a change in the direction of flow of the electric current, and a change in polarity of a voltage which gives the electric current, and thereby effecting the determ

Abstract: A method of detecting the concentration of a component in gases, by an electrochemical element comprising a pumping cell having a first and a second electrode on a solid electrolyte layer, and a sensing cell comprising a third and a fourth electrode disposed on another solid electrolyte layer, the first and third electrodes being located adjacent to each other, and exposed to the gas to be measured which has been diffused with a predetermined diffusion resistance. A primary pumping current is applied to the pumping cell to control the partial pressure of the component in the atmosphere adjacent to the first and third electrodes. The primary pumping current is controlled so that an electromotive force induced on the sensing cell concides with a predetermined value.

Abstract: A method of manufacturing an electrochemical cell for determining the cencentration of a component of a measurement gas, which comprises a solid electrolyte body, and a pair of electrodes which are disposed on the solid electrolyte body and spaced apart from each other, such that one of the electrodes is exposed to the measurement gas via a porous ceramic diffusion layer having a predetermined diffusion resistance to the component of the measurement gas, so that an atmosphere adjacent to the above one electrode is controlled by means of reaction of the pair of electrodes by application of an electric current thereto, the method comprising the steps of: preparing an unfired or calcined laminar structure of the electrochemical cell such that an unfired or calcined layer of the above one electrode is covered by an unfired or calcined layer of the porous ceramic diffusion layer; starting a firing process to fire the laminar structure at predetermined elevated temperatures; applying an electric voltage or current