Robert Boschgmbh

Hermann Dietz

Klaus D Muller

Werner Gruenwald

Karl-Hermann Friese

Ernst Linder

Franz Rieger

Helmut Maurer

Harald Reber

Ferdinand Grob

Ulrich Eisele

Claudio De La Prieta

Gerhard Holfelder

Barbara Beyer

Karl H Friese

Bernd Schumann

Hans-Martin Wiedenmann

Harald Neumann

Werner Grunwald

Lothar Raff

Gert Lindemann

Johann Riegel

Friedrich J Esper

Gerhard Hoetzel

Gunther Stecher

Bodo Ziegler

Carmen Schmiedel

Wolfgang Leibfried

Hermann Fischer

Claudio Da La Prieta

Manfred Koeder

Siegfried Ziegler

Hermann Ziener

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.x), and which is permeable to oxygen. The first cathode, a portion of the solid electrolyte, and the at least one anode form a first pumping cell. The second cathode, another portion of the solid electrolyte, and the at least one anode form a second pumping cell. A measuring signal for determining NO.sub.x is measured between the second cathode of the second pumping cell and the at least one anode of the second pumping cell as a limiting current.

Electrochemical measuring sensor for determining nitrogen oxides in gas

Method and circuit arrangement for acutating a measuring sensor to

Measuring sensor for determining the oxygen content of gas mixtures

Polarographic sensor

Sensor arrangement for determining gas components and/or gas

The invention relates to a measuring sensor having pump reference for measuring the oxygen content of gas mixtures, particularly exhaust gases of internal combustion engines. The sensor includes a measuring cell (A) and a reference cell (B) each having a pair of electrodes, with one of each respective pairs of electrodes being common to the two cells, and having a fixed electrolyte. Reference cell (B) has defined therein an internal oxygen reference zone which is hermetically sealed from the gas mixture and which is connected to the atmosphere by way of a pressure-equalization line. The measuring cell (A) and the reference cell (B) can be heated by heating apparatus to a temperature at which the fixed electrolyte has an ionic conductivity which is sufficiently high. The heating apparatus and a porous insulation are advantageously disposed in the vicinity of the electrode of the reference cell which is not in common with the measuring cell and which is porous so that the porous insulation, together with the porous electrode, form the internal oxygen reference zone and, together with the porous electrode and its porous conductor track, form the pressure-equalization line.

Sensor element for limiting current sensors to determine the lambda

Sensor element for an oxygen limiting current probe in order to

To permit calibrating and testing a current-limiting sensor in situ, the sensor is exposed, from time to time, to ambient air forming a standard gas, and the output thereof compared with a standard, for example by connecting a resistor (4) of standard value in circuit therewith or for recalling from a memory (23) in a microcomputer (22) standard conditions; upon determination of a deviation between output from the sensor (2) when exposed to the standard gas--typically air--and the theoretical value as stored, the theoretical or reference value is reset if the deviation is within a predetermined limit or, otherwise, an alarm output is provided. The tolerance limits can be set in such a way that a first alarm output is provided in a narrow tolerance, thus indicating drift of the sensor toward eventual malfunction, and permitting utilization of the sensor for long lifetime, while providing advance warning of imminent failure. Change of applied voltage to the sensor and test for current therethrough can then derive an actual operating curve which can be compared with stored test curves in the memory from which, upon extrapolation, a tendency to failure can be predicted and recognized.

Method for monitoring operation of a current-limiting type gas sensor

To permit simultaneous evaluation of the light as a consequence of combustion in the combustion chamber of an internal combustion (IC) engine, and evaluation of the oxygen content of the combustion gas resulting from the combustion, a tubular housing of generally spark-plug shape is closed off at the end facing the combustion chamber by a solid electrolyte body in form of a disk (6), closed tube or thimble (6c) or the like, which is made of transparent zirconium dioxide. The interior of the housing has a light guide (7) extending therein. The solid electrolyte body has electrodes (11, 11'; 11c, 11'c) applied thereto, electrically connected to an electrical evaluation stage (EE) to determine oxygen concentration in the combustion gases, while the light due to combustion is transmitted through the solid electrolyte to the light guide for evaluation in an optical evaluation stage (EO). The ceramic body may be ground to form a lens to focus light resulting upon combustion on the light guide which can have a jacket (15) which is electrically conductive to provide one output terminal from the electrodes applied to the solid electrolyte body, the other electrode being connected through the housing to chassis.

Combination gas oxygen concentration and combustion light sensor

To provide for temperature measurement of a solid electrolyte polarographic gas composition sensor, an ac signal is superimposed from an ac voltage source (2) on the applied voltage from a voltage source (1) if the sensor is a polarographic sensor, the ac signal being separated from the output by a filter combination (6, 7), the dc output being evaluated as usual, and the ac output being rectified in a rectifier (9) to obtain a measure of the temperature since the ac resistance (R.sub.alt) is highly temperature dependent (see FIG. 3). The ac preferably is about 10% of the applied dc voltage, so that the voltage swing of the ac potential falls well within the linear range of output current with respect to voltage (see FIG. 2). The output from the ac channel (7, 9) to evaluate the temperature signal can be connected to a control loop circuit (10, 11), including a heater (11) to heat the sensor to maintain a uniform temperature thereof.

Method and apparatus to measure the operating temperature of solid

A method and apparatus is proposed for obtaining a control variable for the closed-loop control of the fuel-air ratio of the operating mixture of internal combustion engines, in which a threshold-current sensor of known structure is used. By means of varying the measurement voltage present at the threshold-current sensor by voltage amounts which correspond to a change in oxygen concentration to be expected in association with a change in operational state, the time behavior of the threshold-current sensor, which is essentially sluggish, is compensated for and it becomes possible to use it for rapidly-functioning closed-loop control systems in internal combustion engines.

Method and apparatus for obtaining a control variable for the

A solid electrolyte is sandwiched between a measuring electrode exposed to the gas and a reference electrode exposed to a reference gas of known oxygen level, and a cover, for example in form of a layer or a cap, is applied over the measuring electrode. To linearize output from the sensor over a wide range of oxygen partial pressure in a gas so that, upon applying a voltage across the electrodes thereof, current flow will be representative of the oxygen concentration in the gas, the cover consists of a material having a predetermined diffusion resistance to oxygen while essentially inhibiting convection of gases to the electrode and limiting the quantity of oxygen reaching the measuring electrode to that value at which any oxygen molecules reaching the measuring electrode will be immediately converted by electrode reaction, thus inhibiting current flow through the sensor due to diffusion of gases and preventing that the current through the sensor will be determined by the activating energy of the charge penetration through the phase separation at the electrode surface.

Polarographic oxygen concentration sensor and method of determining

To permit a layer construction, which is inexpensive and lends itself to mass production manufacture, a solid electrolyte body, in plate-like construction, with electrodes at either thereof is positioned in a housing with a portion thereof extending in the region where it is exposed to gases to be sensed; a porous cover is applied on one of the electrodes, the porous cover having a predetermined diffusion resistance to oxygen molecules. A flat insulating plate of approximately the same dimension as the solid electrolyte plate is positioned flat thereagainst, and a flat layer-like electrical heating element is secured on the flat insulating plate or, in other embodiments, against another insulating covering on the other side of the heating element as well, close to the electrodes and adjacent the plane surfaces of the body. The heating element and the electrodes of the sensing element are carried out as conductive tracks for connection to respective sources of operating or biassing potential and, with respect to the sensing electrodes, to an evaluation circuit.

Electrochemical oxygen sensor, particularly for use with exhaust gases

To facilitate manufacture of a sensor, particularly a polarographic sensor which has no sealing or heat expansion difficulties and only low heat capacity in the measuring range and electrical connections, a solid electrolyte (17) is formed as a plate extending transversely across a bottom opening (13) of a preferably ceramic tube (11), the plate having two electrodes (16,21) applied to its major sides. The side facing the opening (13) is covered with a ceramic layer (20) having a predetermined diffusion or migration resistance to oxygen molecules. The electrical connections are formed by a conductive track (15) extending on the inside of the ceramic tube, in contact with the sensing electrode on one side of the plate; and a counter head (23) connected to a conductive bolt or pin (24) and resiliently spring pressed against the electrode, and holding the plate (17) and the diffusion barrier (20) thereon in position in the sensor. The test gas is applied to the diffusion resistance layer through a ceramic heat storage plate, for instance, having openings therethrough, which has a film-type heater applied thereto, connected to a current source by conductive tracks (31, 31'; 32, 32') positioned on the outside of the ceramic tube.

Gas sensor construction, particularly to determine oxygen content

Growing community of inventors

Gerlingen, Germany

Hermann Dietz