摘要:
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.
摘要:
The invention relates to a method and a circuit arrangement for actuating a measuring sensor for determining an oxygen concentration in a gas mixture, particularly in exhaust gases of internal combustion engines, wherein a detector voltage corresponding to the oxygen concentration and supplied by a reference probe is transferred into a pump voltage for a measuring probe by a circuit arrangement. It is provided that a curve of the detector voltage (U.sub.D) is used directly for determining the curve of the pump voltage (U.sub.P), with a first input (38) of the circuit arrangement (36) being connected to a first input (46) of an adder (48) at whose second input (50) an add voltage is applied and whose output (54) is connected to the second input (40) of the circuit arrangement (36) via an amplifier (58).
摘要:
A measuring sensor for determining oxygen content in a gas mixture including exhaust gases of internal combustion engines, includes a base substrate which is comprised of a base material and which is electrically insulating; and an electrochemical measuring probe and an electrochemical reference probe arranged separate from each other on the base substrate. The measuring probe includes at least one internal electrode; at least one solid electrolyte island; and at least one external electrode. The measuring probe additionally includes a diffusion barrier. Further base material layers composed of the base material are provided so as to embed at least the diffusion barrier, the at least one internal electrodes for the measuring probe and the internal electrode for the reference probe. A diffusion hole is defined between the measuring probe and the reference probe which extends from the base substrate through the diffusion barrier and respective base material layers, and out to the gas mixture to be measured. Thermal stress and the accompanying tendency to cracking is reduced by providing the solid electrolyte as islands. Separate disposition of the measuring probe and the reference probe, i.e., without a common electrode, permits construction as individual layers using, for example, screen printing.
摘要:
A sensor arrangement for determining at least one of gas components and gas concentrations of gas mixtures including CO, NO.sub.x and HC in exhaust gases of internal combustion engines, includes a measuring element which has a sensitive region; and a pump cell that includes a solid electrolyte and inner and outer pump electrodes which are opposingly disposed at least on the solid electrolyte and which effect an oxygen transfer to the measuring element, wherein the pump cell and the measuring element are spatially separated from one another, are located in different temperature zones during operation of the sensor arrangement, and are connected to one another by a diffusion segment through which oxygen can diffuse from the pump cell to the measuring element.
摘要:
A sensor element is proposed for an oxygen limiting current probe for the determination of the .lambda. value of gas mixtures, particularly the exhaust gases of internal-combustion engines, whose oxygen supply is provided by a short-circuit cell disposed upstream of the pumping cell of the sensor element. In this way the CO.sub.2 and H.sub.2 O transverse sensitivity of the sensor element is made ineffective. In order to obtain at the pumping cell a limiting current that is a linear function of the O.sub.2 partial pressure, a diffusion barrier must additionally be disposed between the short-circuit cell and the pumping cell.
摘要:
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.
摘要:
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.
摘要:
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.
摘要:
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.
摘要:
To simplify manufacture and provide a polarographic sensor of high response speed, operating according to the current limiting principle, an oxygen molecule migration barrier is provided leading to the cathode by separating the cathode from the space where the gas to be tested exists by a wall through which a hole is provided which extends therethrough to a small space immediately above the cathode defined by support elements placed immediately on the cathode. The hole, or a plurality of holes, is so dimensioned that the diameter thereof, with respect to its length, is small, with diameters of between 0.01 to 0.06 mm and a length of at least about 1 mm being suitable.