Abstract: The invention relates to a sensor for measuring ion concentration or gas concentration, with a gas- or ion-sensitive layer (6) that has two sensitive partial areas (20 and 21), two conducting areas (1b and 2b), each coupled capacitively through air gaps (9and 10) with one of the sensitive partial areas (20 and 21), with the capacitances of the couplings being different, and a comparison circuit (1a, 2a, 3, 4, 5) which has at least one first transistor (T1) connected with the first conductive area and a second transistor (T2) connected with the second conductive area, and at least one output at which a signal can be tapped that depends on the potential of sensitive layer (6).

Abstract: A limit-current type A/F sensor produces element current responsive to oxygen concentration in the exhaust gas when a voltage is applied to its sensor element portion. An application voltage control circuit comprises an operational amplifier and resistors. An output of the control circuit is applied to one terminal of the A/F sensor via a driver circuit. The other terminal of the A/F sensor is connected to an output terminal of an operational amplifier via a current-detecting resistor. The element current value, detected by the current-detecting resistor, is returned to the application voltage control circuit via a buffer. In the application voltage control circuit, adjustment of the gain is performed in such a manner that the inclination of the application voltage line on the V-I coordinate becomes larger than the inclination equivalent to the A.C. impedance of the sensor element in the sensor activated condition.

Abstract: A control circuit unit which enables an existing NOx sensor to serve not only as an NOx sensor but also as an oxygen concentration sensor by attachment to an existing NOx sensor. A control circuit unit 31 is connected to an NOx sensor 1. A first pump element control circuit 56 controls a voltage applied to a first pump element 3 so as to control the partial pressure of oxygen in a first processing chamber 9 such that an output voltage of an oxygen concentration detection element becomes substantially constant. A first pump current is detected using a current detection resistor 101 and is then output via an A/D converter circuit 65. A second pump element control circuit 57 applies a constant voltage to a second pump element 5 in a direction so as to pump out oxygen from a second processing chamber 10. A second pump current is detected using a current detection resistor 107 and is then output via an A/D converter circuit 65.

Abstract: Methods and devices for determining the concentration of an analyte in a physiological sample are provided. In the subject methods, the physiological sample is introduced into an electrochemical cell having a working and reference electrode. A first electric potential is applied to the cell and the resultant cell current over a period of time is measured to determine a first time-current transient. A second electric potential of opposite polarity is then applied and a second a time-current transient is determined. The preliminary concentration of the analyte is then calculated from the first and/or second time-current transient. This preliminary analyte concentration less a background value is then multiplied by a hematocrit correction factor to obtain the analyte concentration in the sample, where the hematocrit correction factor is a function of the preliminary analyte concentration and the variable &ggr; of the electrochemical cell.

Abstract: The present invention relates generally to a structure, on the surface of the support material of which structure molecular layers are immobilized so as to be electrically addressable, a method for the electrically addressable immobilization of molecules, a device for carrying out this method, and the use of this structure as a chemo- and/or biosensor, in particular as a multisensor system for chemical, biological, and physical assays, and for applications in the combinatorial synthesis on the boundary surface.

Abstract: A circuit configuration for controlling a pump current includes a microcontroller, an analog circuit and a read-only memory. A pulse-width modulated signal, which is output by the micro-controller, is converted, by using the analog circuit, into the pump current for a pump cell of an exhaust probe which operates according to the principle of the galvanic oxygen concentration cell with a solid electrolyte. A pump current actual value is determined from a voltage drop across a measuring resistor, and a pump current setpoint value is determined from a voltage difference between an actual value of a Nernst voltage in the corresponding measuring cell and a predefined setpoint value. An exhaust probe configuration is also provided.

Abstract: In a surface acoustic wave sensor mounted within a body, the sensor having a surface acoustic wave array detector and a micro-fabricated sample preconcentrator exposed on a surface of the body, an apparatus for collecting air for the sensor, comprising a housing operatively arranged to mount atop the body, the housing including a multi-stage channel having an inlet and an outlet, the channel having a first stage having a first height and width proximate the inlet, a second stage having a second lower height and width proximate the micro-fabricated sample preconcentrator, a third stage having a still lower third height and width proximate the surface acoustic wave array detector, and a fourth stage having a fourth height and width proximate the outlet, where the fourth height and width are substantially the same as the first height and width.

Abstract: A method and apparatus for determining the operating condition of a gas sensor apparatus including an amperometric electrochemical sensor operating normally in a potentiostat mode. By coating the sensor with a conductive coating or by varying one or more operating conditions, a response of the sensor can be determined and compared with sensor response while operating normally. This testing enables abnormalities in sensor operation to be determined, and failure of the sensor to be predicted.

Abstract: An oxygen sensor device consisting a cylindrical tube of a ceramic solid electrolyte having an oxygen ion conducting property, a reference electrode formed on an inner surface of the cylindrical tube, and a measuring electrode formed on an outer surface of the cylindrical tube at a position at least opposed to the reference electrode, wherein a ceramic layer is formed on the outer surface of the cylindrical tube, the ceramic layer having an opening portion for exposing the surface of the measuring electrode and incorporating a heat-generating member therein, the heat-generating member being buried surrounding the opening portion. The oxygen sensor device as a whole has a cylindrical shape relaxing the concentration of thermal stress and exhibiting excellent thermal shock resistance. With the heat-generating member being buried near the sensing portion, the sensing portion is heated up to a predetermined activating temperature within short periods of time exhibiting an excellent sensor response.

Abstract: The invention includes systems and methods which allow reactivation of supported noble metal catalysts. The method involves heating the catalyst in the presence of a gaseous hydrocarbon in the absence of oxidizing agents. Systems of the invention provide for in situ reactivation of catalytic material.

Abstract: A sensor array for detecting the distribution of fluids having different electrical characteristics, comprising a multilayer structure including a first layer which defines an array of spaced apart sensor electrodes, a second layer separated from the first layer by dielectric material and defining a conductive screen, and a third layer separated from the second layer by dielectric material and defining a series of spaced apart elongate connections, each sensor being connected to a respective connection by a respective conductive path extending through an opening in the conductive screen defined by the second layer.

Abstract: The Applicant's invention comprises an apparatus and method for determining the amount of one or more components in a pulping liquor. At a first electrode, a varying voltage is supplied in a voltage range including the half-wave potential of each component of a liquor to be measured, and accounting for variations in the half-wave potential caused by changing process parameters. At a second electrode, which is roughly ⅓ to ¼ the size of the first electrode, the derivative of current intensity is monitored near the known half-wave potential for the various liquor components. Using curve-fitting means, the derivative of current intensity and selected other process condition data is used to determine concentrations of the various liquor components.

Abstract: A compact assay system having a solid support has at least one capture binding agent on the support surface. By applying a combination of different binding agents on the support surface, the present invention can conduct multiple chemical reactions on the support solid support to detect analytes of interest. The specific reagents, or capture binding agents, are preferably immobilized on the solid support by means of a computer controlled, miniaturized printing system. Specifically, the reagents can be applied onto the solid support using a commercial available printhead of an ink-jet printer. In addition, the support surface also includes areas adapted to be digitally readable by laser to store information concerning binding between capture agents and analytes. The assay system is useful as a sample array holder for performing a variety of chemical analyses, such as matrix assisted laser desorption ionization mass spectrometry analyses.

Abstract: Arrangement and method for detecting the end of life of an aqueous bath utilized in semiconductor processing, the bath containing water, an amount of hydrogen peroxide and an amount of a predetermined chemical species, which is either an acid or a base, in accordance with the following steps: adding a predetermined additional amount of the hydrogen peroxide and/or the predetermined chemical species at predetermined time intervals, measuring at least one parameter of the aqueous bath, thereby obtaining a measured parameter value, the at least one parameter being selected from a set of parameters including bath pH and bath conductivity; reading a predicted value of said at least one parameter from a memory storing a curve of predicted values of said at least one parameter as a function of time, said curve depending on said predetermined additional amount of said hydrogen peroxide and/or said predetermined chemical species, and depending on said predetermined time intervals; establishing the end of life of said

Abstract: An A/F signal proportional to an oxygen concentration in the exhaust gas from an internal combustion engine is output upon application of a voltage based on an instruction from a microcomputer. At the time an element resistance is detected, a bias instruction signal Vr from the microcomputer is converted by a D/A converter 21 to an analog signal Vb. An output voltage Vc obtained by removing high frequency components from the analog signal Vb through an LPF 22 is input to a bias control circuit 40. During this time period in which the element resistance is detected, an accurate A/F signal is not output. Therefore, the A/F signal that has theretofore prevailed is held by a Sample/Hold circuit 70 to thereby prevent the use of an erroneous A/F signal. Namely, at the time of detecting the element resistance, the detected value of the oxygen concentration is prevented from becoming abnormal. As a result, an accurate A/F control can be executed using the detected element resistance.

Abstract: A gas concentration sensing apparatus includes a gas introducing portion for introducing a measurement gas. A first cell opposed to the gas introduction portion operates for pumping oxygen from the measurement gas in the gas introducing portion. A second cell opposed to the gas introducing portion operates for sensing a concentration in a specific component of the measurement gas from which oxygen has been pumped by the first cell. There is a reference gas chamber to which at least one of the first cell and the second cell is exposed. The one of the first cell and the second cell which is exposed to the reference gas chamber includes an electrode facing the gas introducing portion. A current flowing through the first cell is sensed. A voltage is applied to the first cell in response to the sensed current through the first cell. A current flowing through the second cell is sensed. A voltage is applied to the second cell in response to the sensed current through the second cell.

Abstract: An adjustment circuit and method for reading a measurement output of an automotive oxygen sensor provide correction for outgassing of the sensor and inversion of the measurement output. The adjustment circuit includes a biasing stage connected to a sensor return of the oxygen sensor, where the biasing stage applies a predetermined bias voltage to the sensor return. An input stage is connected to an output of the sensor for retrieving the measurement output from the sensor. The adjustment circuit further includes an A/D conversion system connected to the input stage for adjusting the measurement output based on the bias voltage. The A/D conversion system may further be connected to the biasing stage for retrieving a sensor return output from the sensor. In such cases, a differential module calculates a difference between the sensor return output and the measurement output. The sensor return output defines an actual bias voltage applied to the sensor return.

Abstract: Apparatus for calibrating a pH meter includes a solution chamber for receiving a pH electrode so that a seal is established between the electrode and the wall of the chamber near the top of the chamber. A plurality of inlets are provided into the chamber so that air, a washing solution and a plurality of buffer solutions may be introduced into the chamber below the sealing means, the introduction of these fluids being controlled by valves. The chamber also has a fluid outlet at the bottom of the chamber controlled by a valve. All of the valves are actuated by a programmable controller which also receives a signal from a sensor which senses when the chamber is full of liquid. The controller controls the valves in a pre-determined sequence to pre-clean and fill the chamber with a washing solution, soak the electrode in the chamber for a pre-determined time and then drain the chamber of washing solution.

Abstract: A circuit for improving the resolution of an oxygen sensor in a vehicle exhaust system. The circuit expands a limited output voltage range of an oxygen sensor to full voltage range of an analog-to-digital (A/D) converter, prior to input of the expanded signal into the A/D converter. Utilization of the full range of converter provides improved resolution for analyzing the analog signal.

Abstract: A biologic electrode array assembly is formed on an integrated circuit chip that includes an array of electrodes. At least one metal oxide semiconductor (MOS) switch is coupled to at least one of the electrodes within the array. A voltage line is provided that is selectively connected to the at least one electrode via the MOS switch. A voltage source is coupled to the voltage line. In one preferred aspect of the invention, the MOS switch is a CMOS switch. In another aspect of the invention, an addressable memory is associated with the at least one electrode located within the array.

Abstract: A connector 2b for an NOx sensor is connected via a cable C to an end of a sensor body 2a through which a first pump current and a second pump current flow according to the concentration of oxygen and that of NOx, respectively, contained in a gas to be measured. The connector 2b is provided with not only terminals for inputting a signal to and outputting a signal from the sensor body 2a but also a label resistor RL having resistance corresponding to characteristics (relationship between oxygen concentration and first pump current and that between NOx concentration and second pump current) of the sensor body 2a and label signal output terminals T01 and T02 connected to opposite ends of the label resistor RL.

Abstract: An A/F signal proportional to an oxygen concentration in the exhaust gas from an internal combustion engine is output upon application of a voltage based on an instruction from a microcomputer. At the time an element resistance is detected, a bias instruction signal Vr from the microcomputer is converted by a D/A converter 21 to an analog signal Vb. An output voltage Vc obtained by removing high frequency components from the analog signal Vb through an LPF 22 is input to a bias control circuit 40. During this time period in which the element resistance is detected, an accurate A/F signal is not output. Therefore, the A/F signal that has theretofore prevailed is held by a Sample/Hold circuit 70 to thereby prevent the use of an erroneous A/F signal. Namely, at the time of detecting the element resistance, the detected value of the oxygen concentration is prevented from becoming abnormal. As a result, an accurate A/F control can be executed using the detected element resistance.

Abstract: A control circuit of an exhaust probe has a microcontroller and an analog circuitry. Measured values which are recorded in a test chamber under predefined test conditions are stored in characteristic maps in a programmable read-only memory. These values are then used as a reference for a subsequent recalibration of a probe system.

Abstract: A compact assay system having a solid support has at least one capture binding agent on the support surface. By applying a combination of different binding agents on the support surface, the present invention can conduct multiple chemical reactions on the support solid support to detect analytes of interest. The specific reagents, or capture binding agents, are preferably immobilized on the solid support by means of a computer controlled, miniaturized printing system. Specifically, the reagents can be applied onto the solid support using a commercial available printhead of an ink-jet printer. In addition, the support surface also includes areas adapted to be digitally readable by laser to store information concerning binding between capture agents and analytes.

Abstract: An A/F ratio detecting arrangement includes a sensor casing having an oxygen sensor part arranged between first and second electrodes and an oxygen pump part arranged between third and fourth electrodes, which are heated by a heater. A signal output processing circuit serves to provide an A/F ratio signal. A signal switcher serves to provide a provisional oxygen content signal derived from the first and second electrodes when the oxygen pump part is not activated yet, and the A/F ratio signal when the oxygen pump part is activated.

Abstract: In a method and a device for electrochemical determination of the concentration of at least one dissolved chemical entity in a liquid medium, a measurement voltage U is impressed on a working electrode, in contact with the liquid medium, relative to a counter electrode, thereby causing the dissolved chemical entity to react by oxidation or reduction at the working electrode, producing a measurement evoked current. The measurement evoked current is compared to a predetermined value, and the measurement voltage U is adjusted so that the measurement evoked current is substantially equal to the predetermined value, and thus remains substantially constant during measurements. A difference &Dgr;U=U−Umin is formed, which corresponds to an oxidation/reduction reaction at the working electrode, with Umin being a minimum voltage selected as a reference level. This difference is used to calculate concentration variations of the chemical entity in the liquid.

Abstract: An oxygen concentration detector includes an air-fuel ratio sensor, a heater that heats the air-fuel ratio sensor, a heater controller that supplies electric power to the heater such that the air-fuel ratio sensor reaches an activation temperature, and an element temperature detector that detects a temperature of an element of the air-fuel ratio sensor. The heater controller detects a rate of decrease in the temperature of the element of the air-fuel ratio sensor based on the temperature detected by the element temperature detector, and determines that the sensor element is wetted when the detected rate of decrease is greater than a reference value. The element temperature detector can detect the sensor element temperature based on an impedance of the element. The heater controller can prevent the supply of electric power to the heater if it is determined that the sensor element is wetted. The air-fuel ratio sensor can be provided in an exhaust passage of an engine.

Abstract: A method for determining relative amounts of O2 and N2O in gas mixtures by quantitative electrochemical reaction including feeding a gas mixture containing O2 and N2O to a zinc-air cell having electrodes connected to a circuit consisting of a plurality of diodes and resistors, which circuit is set to have an electrochemical working range corresponding to each of the O2 and N2O; and measuring current flowing in the respective working range to determine the relative proportions of O2 and N2O in the gas mixture. An electrochemical cell including a casing capable of containing a gas mixture, including O2 and N2O a zinc-air cell in the casing, and a circuit connected to electrodes of the zinc-air cell, the circuit containing a plurality of diodes, resistors and tap points; means for measuring current to determine the relative proportions of O2 and N2O in the gas mixture.

Abstract: A diagnostic card device for use in detecting or quantitating an analyte present in a liquid sample, comprising a card substrate having a sample introduction region, a biosensor, and a sample-flow pathway communicating between the sample-introduction region and the biosensor, circuitry for generating an analyte-dependent electrical signal from the biosensor; and a signal-responsive element for recording such signal. In one embodiment, the biosensor includes a detection surface with surface-bound molecules of a first charged, coil-forming peptide capable of interacting with a second, oppositely charged coil-forming peptide to form a stable &agr;-helical coiled-coil heterodimer, where the binding of the second peptide to the first peptide, to form such heterodimer, is effective to measurably alter a signal generated by the biosensor. The sample-flow pathway contains diffusibly bound conjugate of the second coil-forming peptide and the analyte (or an analyte analog) and immobilized analyte-binding agent.

Abstract: A method of controlling and diagnosing the heater of a sensor sensitive to the composition of the exhaust gas of an engine; the sensor having at least an electrolytic cell sensitive to oxygen ions, and supplying information relative to the ratio of the mixture supplied to the engine; the method including the steps of: calculating an internal resistance value of the cell on the basis of detected values of the voltage at the terminals of the cell before and after supplying a reference current to the cell; correcting the calculated internal resistance value as a function of the detected ratio of the mixture supplied to the engine; converting the corrected internal resistance value into a current temperature value of the sensor; feedback controlling the temperature of the sensor by regulating the current supplied to the heater by processing the deviation between the current temperature value and an objective temperature; and diagnosing the efficiency of the heater as of the corrected internal resistance value of

Abstract: The present invention provides a combinatorial approach for preparing arrays of chemically sensitive polymer-based sensors which are capable of detecting the presence of a chemical analyte in a fluid in contact therewith. The described methods and devices comprise combining varying ratios of at least first and second organic materials which, when combined, form a polymer or polymer blend that is capable of absorbing a chemical analyte, thereby providing a detectable response. The detectable response of the sensors prepared by this method is not linearly related to the mole fraction of at least one of the polymer-based components of the sensors, thereby making arrays of these sensors useful for a variety of sensing tasks.

Abstract: A rush current to an oxygen sensor is restricted to very small to secure the high reliability of oxygen sensor. A non-inverting input of an amplifier 30 is grounded. A resistor 31 is connected between an inverting input and an output of said amplifier 30. A limited electric current type oxygen sensor 34 is connected between said inverting input of said amplifier and a reference power supply 33.

Abstract: There is used at least one probe array obtained by arraying particles having various probes, respectively, fixed thereon (probe particles) in a definite order in a holder. A plurality of capillaries or grooves packed with various kinds, respectively, of probe particles are arrayed in parallel, and one of particles contained in each capillary or groove is injected into another capillary or groove to produce a probe array in which the various kinds of probe particles are arrayed in a constant and definite order. Various fluorophore-labeled DNA's are measured at the same time by attaching various probes to particles, respectively, of different sizes. A probe array composed of various fixed DNA probes can easily be produced, and there can be provided a probe array for detecting various DNA's which is composed of various fixed arbitrary DNA probes.

Abstract: A measuring device (1) for measuring or investigating physiological parameters using biological cells or chemical and biologically active substances contained in an analyte (2). The measuring device comprises a sensor (4) with an electronic measurement structure (6) located on a substrate (5). Function-specific receptor cells and/or target cells (7) form part of the sensor (4) and are in direct contact with the measurement structure (6). For measurement, the medium under investigation can be brought into contact with the target cells or receptor cells (7). The measuring device (1) is especially compact in its design and facilitates largely feedback-free investigation of biological or chemical components contained in the analyte.

Abstract: An electrochemical cell sensing circuit for an electrochemical cell having a working electrode, a counter electrode and a reference electrode in an electrolyte, which in use, when a gas to be analysed is introduced into the cell, generating a current between the counter electrode and the working electrode, and a potential at a position in the electrolyte is sensed by the reference electrode.

Abstract: A main heater consisting of first and second fever areas and auxiliary heater arranged on an insulator substrate to maintain a precise sensing temperature. Grounded first fever area is contiguous with second fever area and grounded auxiliary heater, with the resistance ratio of first fever area and second fever area identical to that of the third resistor and the second resistor in bridge circuit control. Pyro-sensor or limit current type oxygen sensor capable of maintaining a high temperature, for example 400° C., operates within the high temperature maintained by the main heater, and DC—DC converter for isolating a first power supply, which supplies electric power to the heater from second power supply. Leakage current of the insulator substrate will not be generated as the insulator substrate deteriorates, thereby protecting the sensor cell leakage current from the heater.

Abstract: A method of operating a H2—O2 fuel cell fueled by hydrogen-rich fuel stream containing CO. The CO content is reduced to acceptable levels by injecting oxygen into the fuel gas stream. The amount of oxygen injected is controlled in relation to the CO content of the fuel gas, by a control strategy that involves (a) determining the CO content of the fuel stream at a first injection rate, (b) increasing the O2 injection rate, (c) determining the CO content of the stream at the higher injection rate, (d) further increasing the O2 injection rate if the second measured CO content is lower than the first measured CO content or reducing the O2 injection rate if the second measured CO content is greater than the first measured CO content, and (e) repeating steps a-d as needed to optimize CO consumption and minimize H2 consumption.

Abstract: The apparatus of the invention includes a flow chamber having an inlet, an outlet, and a removable cover. The cover includes fittings for mounting a reference electrode assembly, a measuring electrode assembly, and a combined counter electrode/thermistor probe. According to the one illustrative embodiment invention, the flow chamber is substantially cylindrical with the inlet located near the bottom of the chamber and the outlet located near the top of the chamber. The axes of the inlet and outlet lie in the same plane as and are parallel to a diameter of the chamber. The inner diameter of the inlet is reduced to approximately ⅛″ so that the velocity of water entering the chamber is increased. The inner diameter of the outlet is approximately ¼″ so that the velocity of water exiting the chamber is less than the velocity of water entering the chamber.

Abstract: An operational amplifier (34) has its inverting input connected to a electrochemical gas sensor (38) for amplifying the current produced thereby in response to presence of a predetermined gas. In order to determine whether a sensor (38) is indeed present and that a sensor present is serviceable, a transient is applied to the non-inverting input of the operation amplifier (34). The presence or absence of the sensor (38) alters the transfer function of the operational amplifier (34) in respect of the test signal. If a serviceable sensor (38) is present, the gain of the operational amplifier (34) is high for the transient resulting at square pulse output. However, if a serviceable sensor (38) is not present, the gain of the operational amplifier (34) is relatively low and the transient retains its original form. Consequently the presence of a serviceable sensor (38) can be determined from the output of the operational amplifier (34) in response to the transient test signal.

Abstract: The invention is directed to a diagnostic arrangement for a potentiometric, electrical exhaust-gas probe for the control of combustion processes with a periodic change of the composition of the combusting air/fuel mixture between oxygen deficiency and oxygen excess. The exhaust-gas probe is heated by an electric heater and outputs a probe signal when the exhaust-gas probe operates without fault which changes between a first region of high signal values (oxygen deficiency) and a second region of low signal values (oxygen excess) with the first region and the second region being separated by a third region of values. A fault announcement is outputted when the probe signal lies within the third region longer than a pregiven longest duration. A fault announcement is also outputted when changes of the current supplied to the electric heater occur within the pregiven longest duration and when the probe signal has temporarily left the third region of values after the change of the heater current.

Abstract: A method and corresponding apparatus useful for the in situ measurement of atomic hydrogen permeation into carbon steel from process streams under operating conditions of up to 3000 psi and temperatures up to 300° F.

Abstract: The control arrangement comprises an oxygen linear test sensor located along the exhaust duct of an internal combustion engine, the sensor having a chamber able to receive part of the exhaust gas and two electrolytic cells of which one is electrically piloted; the arrangement having a retro-operation test circuit able to adjust the current piloted to the cell to give rise to an oxygen ions draining mechanism from and/or towards the chamber which induces the stoichiometric condition within the chamber itself, and an outlet circuit able to convert the piloted current into a first signal representative of nature of the mixture fed to the engine; the arrangement being provided with a memory circuit which memorises the value of a compensation resistance of the eventual spreads of the piloted current of a correcting circuit receiving the stored value of the compensation resistance and able to ensure a correction for the first signal to recover the spreads of piloted current to the cell; the correcting circuit provi

Abstract: A device for automatically measuring a concentration of a developing agent in a developing bath includes a voltage generator capable of generating at least one voltage ramp provided to feed a three-electrode cell; a potentiostat provided to maintain a constant potential difference between two electrodes; a peak detector provided to identify the maximum current flowing in the three-electrode cell that corresponds to the developing agent concentration; and a display unit provided to show the maximum current.

Abstract: A control device for an air-fuel ratio sensor for detecting, from an oxygen concentration detecting device, a current corresponding to a concentration of oxygen contained in a gas by applying a voltage to the oxygen concentration detecting device. The control device detects an alternating impedance of the oxygen concentration detecting device corresponding to each frequency by applying alternating voltages of a plurality of frequencies to the oxygen concentration detecting device and analyzing each of the alternating impedances detected by the impedance detecting means so as to calculate a parameter indicating a change in the characteristic of the oxygen concentration detecting device, and thereby achieve control of the air-fuel ratio sensor.

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: An electrochemical assay includes a method for determining with great accuracy the time at which an applied sample bridges a gap between the electrodes of an electrochemical cell. The method involves applying a constant small current across the gap, while monitoring the potential difference between the electrodes. The time at which the sample bridges the gap is marked by a sharp drop in the potential. A constant voltage is applied after the sample is detected, and the current and/or charge through the sample is monitored over a period of time. From the measured current or charge, the analyte concentration of interest can be calculated.

Abstract: An electronic sensor is described that includes a sample receptacle and a data storage device. The data storage device is powered by a pair of half cells on the sensor. The half cells contain ion solutions that are also used to calibrate the sensor. As the sensor is placed within a sensor data reader, the data stored on the data storage device is transferred to the reader along with measurements of the voltage potential between the half cells. The reader thereafter calculates a calibration slope curve for the sensor. The calibration slope curve is then used to determine the exact ion concentration of any sample that is placed in the sample receptacle.

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 oxygenate additive analyzer is provided which detects and determines the presence of oxygen enhancing additives in gasoline or other fuels. The oxygenate additive analyzer includes a portable electronic controller with a fuel cell connected to the controller by a ribbon cable. In operation, a sample of the fuel to be tested is placed in the fuel cell and electrical control signals are transmitted between the controller and the fuel cell. The analyzer measures the direct current conductivity, resonant frequency, and temperature, and such data is analyzed on the unique software system in the microprocessor of the controller. Upon the completion of the fuel analysis, the controller displays the percentage, if any, of added oxygen by weight, lists probable oxygenates as a percentage of volume, and shows the temperature of the fuel sample. The analyzer is a portable unit with a battery power supply.

Abstract: An operational amplifier (34) has its inverting input connected to a electrochemical gas sensor (38) for amplifying the current produced thereby in response to presence of a predetermined gas. In order to determine whether a sensor (38) is indeed present and that a sensor present is serviceable, a transient is applied to the non-inverting input of the operation amplifier (34). The presence or absence of the sensor (38) alters the transfer function of the operational amplifier (34) in respect of the test signal. If a serviceable sensor (38) is present, the gain of the operational amplifier (34) is high for the transient resulting at square pulse output. However, if a serviceable sensor (38) is not present, the gain of the operational amplifier (34) is relatively low and the transient retains its original form. Consequently the presence of a serviceable sensor (38) can be determined from the output of the operational amplifier (34) in response to the transient test signal.