Abstract: An electrochemical gas sensor for detecting gaseous components in the environment has a diffusion membrane, a measuring electrode, a counterelectrode, and, if desired, a reference electrode, pressed together in a disk stack, which are accommodated in a pot-shaped cover, which in turn is beaded around the sealing edge (6) of a housing pot (1). A compression spring (21) in the housing pot (1) presses a wick disk (20) against the measuring electrode (12), so that a constant and pressurized, intimate and sealed positioning of the disk stack is guaranteed. It is achieved as a result that no additional contact leads from the electrodes to the outer space of the sensor to the measuring and evaluating unit are needed, so that leakage-free sealing of the sensor to the outside is possible, and that a constantly stable, reproducible measured signal is obtained because of the defined and narrow electrolyte film on the surface of the measuring electrode.

Abstract: A gas or fluid pressure or force sensor is disclosed consisting of a fluid-tight housing containing a supply of electrochemically active gas and an electrolytic membrane disposed to divide the housing into two chambers. The electrolytic membrane has one or more pervious electrodes disposed on each side of and in contact with the membrane. A flexible bellows or diaphragm is disposed to form one wall of the fluid-tight housing and provide the contacting surface for transferring a force or pressure to the sensor. A controller is connected to display measurements and to permit automatic sensor calibration, differential pressure-induced diffusion compensation, temperature compensation and sensor chamber pressure control. The disclosed force sensor is useful for application to robotic manipulators and the basic device is useful for measurement of the gas partial-pressure of a selected gas.

Abstract: An industrial process oxygen analyzer, and method of using same, incorporates an automotive oxygen sensor to minimize the criticalness of controlling heater temperature during operation. Higher sensor heater temperature, required to accommodate the automotive oxygen sensor, is achieved by application of higher supply voltage to the sensor heater. Current limiting of the heater supply circuit reduces stress on the sensor heater, even at the higher operating temperature.

Abstract: The invention relates to a sensor system for determining the moisture content in a gas to be measured. On the basis of two current saturation ranges during the determination of the moisture content with the aid of a zirconia sensor, according to the invention two spatially separated sensors are provided, which are operated at different voltages corresponding to the individual saturation current ranges. By further evaluation of the signals, this permits a very precise, on-line determination of the moisture content of the gas to be measured.

Abstract: A closed loop fuel control system for an internal combustion engine in which the temperature of the exhaust gases passing by the oxygen sensor are regulated. The system utilizes a heated oxygen sensor in a slipstream of the exhaust gas and the temperature of the exhaust gas is controlled prior to its passing by the heated oxygen sensor for maximum efficiency of the catalytic converter.

Abstract: A method of compensating an output of a sensor adapted to determine an air/fuel ratio of an air-fuel mixture, depending upon an oxygen concentration of an exhaust gas produced as a result of combustion of the air-fuel mixture, wherein the sensor includes a sensing element which has at least one electrochemical cell each having an oxygen-conductive solid electrolyte body and at least one pair of electrodes The method includes the steps of detecting at least one parameter selected from the group consisting of a temperature Tc of the sensing element, a pressure Pg of the exhaust gas, and a temperature Tg of the exhaust gas, and adjusting the output y.sub.0 of the sensor, based on the at least one parameter detected, to obtain a compensating output of the sensor.

Abstract: A method for determining the pH of liquids by a pH difference measurement of a solution under test and a reference solution and an apparatus for determining the pH of liquids is provided which can determine the pH with a precision equal to or better than 0.001 pH. The method and apparatus are especially useful for determining the pH and development speed of developers for positive photoresists.

Abstract: An accurate, low cost temperature control system for a disposable cartridge carrying including a sample chamber for a portable medical diagnostic device or other electrochemical analytical device is disclosed. The disposable cartridge may include its own heating element on a sensor chip and plugs into a terminal which contains electrical input/output connections. The outer surface of the chip is exposed. A remote temperature sensor which senses the temperature of the outer surface of the chip of the measuring cell and generates a control signal which is used with conventional temperature control circuitry as the basis for thermostatic control of the cell temperature.

Abstract: A probe for continuously measuring the precise concentration of liquid ethanol in a fermentation broth over the range of feasible fermentation temperatures. The probe includes a thermal sensor, a gas permeable membrane leading to a vapor channel, an ethanol vapor sensor in a vapor sensing chamber, and a microcomputer. The microcomputer is loaded with a first set of data defining the initial parameters of the fermentation broth and a set of data defining the ethanol diffusion rate through the gas permeable membrane as a function of the temperature of such fermentation broth. Inlet and outlet connection and tubular interconnections are provided for leading a flushing gas through the vapor channel, past the ethanol vapor sensor and out a vent outlet. Electrical lines leading from the thermal sensor to the microcomputer provide an input signal which is proportional to the temperature of the fermentation broth.

Abstract: An improved flow-through type electrode assembly includes an insulating transparent housing member having a transverse sample liquid passageway. A hollow cylindrical cathode forms a portion of the passageway and is physically displaced from a removable anode member that can be resiliently positioned in the passageway. A series of similar electrode assemblies can be interconnected together.

Abstract: In connection with a method for generating a constant derivation potential in analytical chemistry by means of a pH measuring chain containing a reference electrode, in particular for a pH test electrode for use in the meat-processing industry or for measurements in semi-solid substances such as cheese, pastes, in which for carrying out the measurement at least the pH measuring electrode is introduced into the medium to be measured by a corresponding movement, it is proposed that every time the pH measuring electrode is introduced into the medium to be measured, the electrolyte solution of the reference electrode, which is to be brought into contact with the medium to be measured via a diaphragm, be compressed whereby the diaphragm of the reference electrode, which gets into contact at least with the outer surface of the medium to be measured, is subjected to a cleaning action due to the pressure rise in the electrolyte solution occurring simultaneously with such compression.

Abstract: An electrochemical device such as an oxygen sensor comprising: a plurality of solid electrolyte bodies; at least one pair of electrodes, each pair being disposed such that the electrodes are held in contact with the solid electrolyte bodies separately; at least one conductor sandwiched by two adjacent conductors of the solid electrolyte bodies; and at least one electrical insulation layer. A substantive portion of at least one side of the conductor indirectly contacts one of the two adjacent solid electrolyte bodies via the electrical insulation layer which is disposed therebetween, whereby the conductor is protected from direct contact with the associated solid electrolyte body. The insulation layer further serves to prevent noises which could otherwise be produced due to leakage current from the conductor. The conductor may be a lead connected to one of the electrodes, or to a heater for heating a portion of the solid electrolyte body adjacent the electrodes.

Abstract: An apparatus is provided for rapidly determining the biochemical oxidation demand (BOD) of a liquid at an on-site location. The apparatus includes a cell body member having a vertically extensive plunger chamber formed therein and a sample holding chamber communicating therewith, a dissolved oxygen sensor for generating a signal in proportion to the amount of dissolved oxygen content in a liquid sample and a culture medium disposed in the sample holding chamber, and a tubular plunger member extensive into the plunger chamber for supporting the dissolved oxygen sensor such that the dissolved oxygen sensor extends into the sample chamber and into contact with the liquid sample and the culture medium.

Abstract: A probe adapted for insertion in living tissue for measuring oxygen partial pressure and temperature at a plurality of sites in living tissue is provided. A temperature sensitive resistor is positioned adjacent each of a plurality of oxygen sensors so that the oxygen partial pressure measured can be adjusted for tissue temperature. The probe substrate has thermal properties similar to living tissue and the resistors are formed of a material having a temperature sensitive resistance. Temperature at each temperature sensitive resistor is obtained by measuring resistance with a four point measurement and correlating the resistance to temperature.

Abstract: An industrial process oxygen analyzer, and method of using same, incorporates an automotive oxygen sensor to minimize the criticalness of controlling heater temperature during operation. Higher sensor heater temperature, required to accommodate the automotive oxygen sensor, is achieved by application of higher supply voltage to the sensor heater. Current limiting of the heater supply circuit reduces stress on the sensor heater, even at the higher operating temperature.

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: A method of measuring an ion-concentration characterized by a sample absorbed in an easily absorbing solution material and the absorbing material is brought into contact with a measuring portion to measure an ion-concentration 10/90 in the sample so that a highly accurate measurement can be achieved even though a quantity of the sample is small. In addition, the desired measurement can be carried out without using any instruments for sampling and needing any complicated pretreatments. A sheet for use in the calibration of an ion-concentration 10/90 measuring device characterized by a calibrating buffer solution absorbed in a chemically stabilized, hygroscopic, water-absorbing sheet eluting no ions and then the water-absorbing sheet is dried.

Abstract: A temperature control device for an oxygen concentration sensor having a solid electrolytic member having oxygen ion-conductivity, a gas diffusion-limiting zone defined by the solid electrolytic member and into which is introduced a gas the concentration of which is to be examined, and a couple of electrodes between which the solid electrolytic member is interposed. Pumping current is supplied to the solid electrolytic member and flows therein between the electrodes to cause an oxygen ion flow in the solid electrolytic member between the electrodes to vary the concentration of oxygen present within the gas diffusion-limiting zone. The pumping current is varied in response to the concentration of oxygen within the gas diffusion-limiting zone, whereby the concentration oxygen in the gas is detected from the pumping current value.

Abstract: The invention is directed to a measuring cell for an electrochemical gas sensor having an electrolytic chamber and a measuring electrode as well as a counter electrode. In the direction facing the ambient, the measuring electrode includes a diffusion membrane as well as a diffusion barrier. The diffusion barrier is made of a material which is a good conductor of heat and is provided with a plurality of passages. A temperature-sensitive element is provided in the immediate proximity of these passages and faces toward the ambient. With this configuration, the temperature dependency of the diffusion capacity of the gas sample passing through the diffusion barrier can be included in the processing of the signal indicative of the measurement.

Abstract: An electrode unit for use in an analyzer of blood and of liquids includes a cylindrical outer housing having open ends and a pair of top hat end plate bushings each having a central bore and a plug portion, the bushings being positioned in each end of the housing with the plug portion directed into the housing to form a filling chamber with the inner surface of the housing. A sodium glass capillary tube is mounted in the bores of the bushings. An annular groove is formed in an end flange portion of each bushing so that a connecting alignment ring may seat in the bushing annular grooves of two adjacent electrode units to center the electrode units.

Abstract: The invention relates to a sealing and insulating construction of a sensor for pressurized working conditions. The construction comprises a pressure balancing chamber (1) which is open towards the pressurized space, a sensor (4) which is partly located within the chamber and partly protrudes therefrom, as well as a conductor (6) insulated from the housing (2) and coupled to the sensor (4), and brought into the chamber via a leadthrough (5). Moreover, the construction includes insulation (7) for filling the space that surrounds the chamber around the sensor, as well as a piston (8) for separating the insulation around the sensor from the pressurized space, so that under pressure the sensor is evenly loaded on all sides, and consequently not subject to such tensions that could break it.

Abstract: An oxygen concentration-sensing device has an oxygen concentration-sensing element which senses the concentration of oxygen contained in a gas, and a heater which heats the sensing element. A control device is electrically connected to the heater for controlling the supply of electricity to the heater so as to bring the temperature of the heater to a desired temperature. A coupler connects between the sensing element and the control device. A compensating resistance is accommodated in the coupler, which has a resistance value corresponding to a resistance value of the heater assumed at the desired temperature. The control device controls the supply of electricity to the heater based upon electrical information obtained from the compensating resistance.

Abstract: A field-effect transistor-type semiconductor sensor is provided which comprises first and second semiconductor substrates bonded strongly to each other interposing a silicon oxide film therebetween by the use of a direct-bonding technique. The first semiconductor substrate is formed into an island-shape, and incorporates a source region, a drain region and a gate region. The island-shaped substrate constitutes an ion-sensitive portion, and is immersed in a solution when in use. The second semiconductor substrate has openings in which source and drain electrodes are formed.

Abstract: Flexible measurement probes are described for the determination of oxygen partial pressure; temperature and perfusion; and combined measurement of oxygen partial pressure, temperature, and perfusion. The probes are fabricated by patterning a metal coated substrate to form a conductive pattern of ribbon leads, insulating the conductive ribbon leads except for contact openings, and then attaching sensors to the conductive ribbon leads through noble metal plated open contacts. The plated contacts may be used directly to measure oxygen partial pressure.

Abstract: An electrolytic cell, e.g., for the electrolysis of NaCl to produce chlorine and sodium hydroxide, has an improved operation control system, such system including a plurality of means for monitoring and controlling the flowstreams of inlet starting materials and/or outlet final products, the temperature of the electrolyte, the various reagent concentrations and the cell current, and such plurality of means being operably connected to a computing function which carries out corrective coherence calculations on certain of the parameters of electrolysis and adjusts the operation of the cell in response thereto.

Abstract: An electrochemical gas sensor having a flexible membrane mounted at the sensing end of a housing, to dissipate increased electrolyte pressure, a small sensing electrode cooperating with a relatively thick porous sheet of polytetrafluoroethylene (PTFE) supported by the flexible membrane, and the housing also containing an electrolyte and a counter electrode, with suitable circuitry connected to the electrodes for quantifying the current generated by the sensor.

Abstract: A microprocessor-controlled pH and ion concentration meter is disclosed with improved calibration and testing procedures. For calibration (standardization), the meter stores number pairs (pX.sub.a, E.sub.a), (pX.sup.b, E.sub.b) where the pX values may be pH values (e.g., 4.00 and 7.00) and the E values are expressed in mV/deg K. When multiple standard values are stored, remeasuring one (e.g., replacing E.sub.a1 by E.sub.a2) can be used to update the others (e.g., E.sub.b1 to E.sub.b2) without remeasurement by applying the formula:E.sub.b2 =E.sub.b1 +(E.sub.a2 -E.sub.a1).Additionally, the meter can be tested for excessive internal bias current by measuring the potential (V1) when the meter is connected to a circuit of low impedance and the potential (V2) when the meter is connected to a circuit of the same voltage source but of known high impedance and having the meter compare (V2-V1) to a preset limit value.

Abstract: The invention is directed to a measuring cell for detecting a component of a measuring sample. The measuring cell includes a housing in which an electrolyte as well as a measuring electrode and a counter electrode are accommodated. A membrane separates the electrolyte from the measuring sample and is pressed by a supporting part against the measuring surface of the measuring electrode. This membrane is improved such that it can compensate for volumetric changes in the electrolyte chamber in the clamped condition. The measuring cell is further improved in that a small amount of readiness energy is required for the operational-ready condition and the attachment of the membrane is not critical for its later function. A first portion of this membrane is pressed against the measuring electrode. In the region outside of this first portion and extending up to the peripheral edge where it is attached, a compensating membrane portion is formed which can change in its configuration.

Abstract: A gas sensing element having a co-fired laminar structure including an electrochemical cell having a planar solid electrolyte body, and at least two electrodes disposed on the planar solid electrolyte body. The sensing element further includes two generally planar heaters which are formed on opposite sides of the electrochemical cell, respectively, and which are spaced apart from each other in a direction perpendicular to the planar solid electrolyte body, and a generally planar thermosensitive portion formed as an integral part of the laminar structure, for detecting a temperature of the laminar structure in the neighborhood of at least one of the electrodes of the electrochemical cell. The thermosensitive portion may partially define a diffusion chamber into which a measurement gas in an external space is introduced under a predetermined diffusion resistance, so that one of the electrodes is exposed to the introduced measurement gas.

Abstract: A readily manufacturable heated solid electrolyte oxygen sensor. A heater subassembly readily adaptable to unheated oxygen sensor technology, provides a greater reference oxygen gas source to the reference electrode of the solid electrolyte body, in addition to being positioned and rigidly secured within the oxygen sensing device.

Abstract: A chemical process control system includes a plurality of sensors for sensing various parameters of several baths employed in a chemical process. A microprocessor is employed to interrogate each sensor, to determine bath characteristics from one or more of the parameters, and for comparing the parameters to established limits. The microprocessor initiates corrective responses whenever a characteristic falls outside its specific limits in an attempt to restore the characteristic to a specified operating target value.A hierarchy of authorization keys limits access to the apparatus depending upon the level of authority of the person seeking access. Different degrees of authority may be delegated for an apparatus operator, a supervisor and servicing personnel. The apparatus includes a local and remote communication capacity for sending messages concerning malfunctions in the apparatus and for receiving instructions from a remote location for correcting malfunctions.

Abstract: An oxygen concentration measuring device having a very small size detecting portion formed of unitary lamination of plate shaped members of an oxygen sensing element, a heater member and/or a temperature detecting member. The element comprises an oxygen concentration cell and a temperature compensation means for compensating a setting voltage to which an EMF generated by the concentration cell is compared. The detecting portion is provided with a printed contact terminal and housed in a probe equipped with a protecting tube. The printed contact terminal of the detecting portion is arranged to mate with a connecting element housed in a funnel-shaped contact member so as to allow easy mounting and detaching.

Abstract: The invention relates to a microelectrochemical electrode structure comprising a monolithic substrate having a front surface and a back surface facing generally away from one another, a first well extending into the substrate from the surface towards the back surface and ending in a first well bottom, and a first passage extending into the substrate from the back surface to the first well bottom. A first electrode is located wholly within the first well. A first conductor in the first passage serves for electrically communicating the first electrode to adjacent the back surface. A plurality of such electrode structures can be provided on a single substrate. The use of semiconductor processing technology allows the entire sensor to be extremely small. If desired, an integrated circuit can be provided on the back surface of the substrate for amplifying or otherwise processing signals from the first electrode. Analysis can be carried out for vapors or dissolved species (ionic or non-ionic).

Abstract: The measuring probe is equipped with a pellistor and renders possible directly determining in a trouble-free manner volatile constituents which are contained in a liquid medium to be investigated and which can be chemically converted with an accompanying heat effect. Heating devices are provided and, due to the prevention of condensate formation, greatly contribute to obtaining high measuring precision. The response time of the measuring probe can also be significantly reduced by heating a membrane which separates a measuring space containing the pellistor from the liquid medium to be investigated. The measuring probe can be used with advantage for monitoring microbiological processes, for example, in a fermenter.

Abstract: A process control system for a filter press membrane electrochemical cell is provided that utilizes a microcomputer for multi-tasking functions to concurrently execute four programs to control the cell operation and self-correct out-of-tolerance conditions or shut cell operation down if not corrected within the allotted time period. A core process control program intercommunicates with a timer program, an alarm monitoring program and at least one sequence program in the process control system.

Abstract: Electric conductivities of an aqueous solution under measurement are measured at two or more different temperatures in a range To to Tn, and a relationship between the electrical conductivity and the temperatures is obtained. A solute substance in the aqueous solution is determined by applying this relationship against a known temperature and electrical conductivity relationship of an individual substance. A concentration of the determined substance is estimated by applying the electrical conductivity at the lowest temperature To to a known relationship between an electrical conductivity and a concentration at the same temperature To with respect to an individual substance.

Abstract: The combination of a measured value transmitter unit, a metering unit and a control unit enables all maintenance measures which become necessary during the course of process monitoring, to be carried out with little expenditure of labor and time and without removing the sensor from the container containing the measured medium. In addition, this combination, in which all functions necessary for carrying out the maintenance can be initiated and/or controlled by pneumatic signals, permits at least partial automation of the maintenance.

Abstract: An external, reference electrode is provided for long term use with a high temperature, high pressure system. The electrode is arranged in a vertical, electrically insulative tube with an upper portion serving as an electrolyte reservior and a lower portion in electrolytic communication with the system to be monitored. The lower end portion includes a flow restriction such as a porous plug to limit the electrolyte release into the system. A piston equalized to the system pressure is fitted into the upper portion of the tube to impart a small incremental pressure to the electrolyte. The piston is selected of suitable size and weight to cause only a slight flow of electrolyte through the porous plug into the high pressure system. This prevents contamination of the electrolyte but is of such small flow rate that operating intervals of a month or more can be achieved.

Abstract: A flat shaped composite electrode includes a flat substrate having a high electrical insulating property. A flat inside pair of electrodes and a flat outside pair of electrodes are fixed on the substrate. A flat support layer having a high electrical insulating property overlays the electrodes and substrate. The support layer describes two holes into which a gelatinized internal solution is placed. An ion response glass membrane is mounted on the support layer and over one hole, while a liquid junction membrane is similarly mounted over the other hole.

Abstract: Disclosed is a solid-type ion sensor which does not have an internal liquid chamber. The ion sensor has a laminated structure basically includes an electrically conductive substrate, a redox layer having a redox function covering the surface of the electrically conductive substrate, and an ion-selective layer covering the surface of the redox layer. Also provided is an ion sensor of this type having an insulated thermister imbedded so as to contact the redox layer.

Abstract: Electrochemical sensor cells having reduced zero current temperature sensitivity comprise a working electrode and a counter electrode in close proximity and in contact with an electrolyte. Both electrodes are exposed to the atmosphere to be tested and at least a portion of the counter electrode is masked from the electrochemically active gas in the atmosphere.

Abstract: During the measurement of oxygen content of a gas with a solid electrolyte material capable of oxygen ion conductivity the electrolyte is heated to maintain a constant control temperature. If the ambient temperature changes, an offset or error is introduced into the oxygen measurement. An apparatus and method is provided to automatically compensate for any such offset. Thermocouple means are provided in series with the electrolyte circuit so that a thermal emf if generated due to any differential between ambient and control temperatures. The thermocouples are arranged to generate a net thermal emf which opposes the emf generated by the electrolyte by an amount which automatically compensates for any offset due to the temperature differential. If the ambient and control temperatures are the same, there will be no offset and no net thermal emf.

Abstract: An oxygen concentration detection device having a pair of oxygen pump units includes an oxygen-ion conductive solid electrolyte member a surface of which faces a gas retaining chamber. A measuring gas is introduced through a gas restricted region into the gas retaining chamber. The solid electrolyte member is provided with two pairs of electrodes respectively supplied with a pair of pump currents generated by a current supply circuit. The magnitude of the pump current flowing between the electrodes of one of two pairs of electrodes is controlled so that the voltage difference across the electrodes of the other one of the two pairs of electrodes is maintained at a level corresponding to a reference level. The oxygen concentration in the gas retaining chamber is detected in terms of a sum value of pump currents flowing through the two pairs of electrodes.

Abstract: An electrochemical cell for use in gas detection includes a cell body having an electrolyte cavity and a separate sensor cavity. The sensor cavity holds stacked sensor elements including a counter electrode, electrolyte mat, reference electrode and sensing electrode. A wick draws the electrolyte from the electrolyte cavity to the electrolyte mat. The sensing electrode closes off the sensor cavity and seals the counter and reference electrodes therein. The only gas which contacts the counter and reference electrodes is that which passes through the sensing electrode or is generated by the counter electrode and becomes dissolved in the electrolyte.

Abstract: Oxygen partial pressure and temperature are measured in living tissue by inserting a thin probe into living tissue. The probe includes a plurality of spatially separated thermal sensors secured to the probe substrate. A plurality of oxygen sensors is positioned along the length of the probe substrate and each oxygen sensor is associated with and positioned adjacent to or is an integral part of one of the thermal sensors. Electrical parameters of the sensors located on the probe are measured and used to determine oxygen partial pressure and to determine temperature at each of a plurality of sites along the probe.

Abstract: An oxygen sensor including an oxygen sensing element having one closed end and inner and outer electrode layers formed on the inner and outer surfaces thereof, an output withdrawing lead wire electrically connected to the inner electrode layer formed on the inner surface of the oxygen sensing element, and a metallic terminal disposed in connection between the output withdrawing lead wire and the inner electrode layer. The metallic terminal includes opposed resilient portions separated by a gap and disposed in contact with the inner periphery of the inner electrode layer to apply a radial force to the inner electrode layer, whereby not only the damage of the oxygen sensing element is prevented but also the mounting operation can be done easily without threaded insertion of the metallic terminal.

Abstract: Energization of a heater built in a gas sensor, such as an oxygen sensor, used in an air/fuel ratio control system of an internal combustion engine, is controlled to maintain the temperature of the same within a desired range. The temperature of the heater is calculated using a measured resistance value of the heater, and engine parameters used for estimating a specific engine operating condition. To this end operating state of the engine is first detected to determine whether it is possible to estimate the actual temperature of the heater, and when possible, a reference resistance value of the heater at a reference temperature such as 0.degree. K. or 0.degree. C. is caluclated using estimated heater temperature and a measured resistance value. Once the initial resistance value is obtained, this is used to calculate actual heater temperature using measured resistance value and a predetermined temperature coefficient.

Abstract: The invention relates to a control system for feedback control of the air/fuel ratio in an internal combustion engine by using a solid electrolyte oxygen sensor to sense oxygen in the exhaust gas. The oxygen sensor is of the type having an oxygen concentration cell and an oxygen ion pump cell to which a pumping current is supplied to vary the partial pressure of oxygen in the exhaust gas admitted in a measurement space in the sensor. The pumping current is controlled so as to nullify a difference between the output voltage of the oxygen concentration cell and a target voltage. A signal derived from the controlled pumping current is used as an air/fuel ratio signal on the premise that a definite correlation exists between the magnitude of the pumping current and the oxygen concentration in the exhaust gas.

Abstract: Apparatus comprising an ammonia electrode, a pH electrode and a thermistor is utilized in determining ammonium in concentration and total ammonia concentration by simultaneously measuring to produce signals related to ammonia concentration, hydrogen ion concentration and temperature. Ammonium ion concentration and total ammonia concentration are calculated based on the equation [NH.sub.4.sup.+ ]=[NH.sub.3 ][H.sup.+ ]/K where K is the equilibrium constant for the reaction NH.sub.3 +H.sup.+ .revreaction.NH.sub.4.sup.+ at the temperature measured by the thermistor. In a preferred embodiment a microprocessor is included for the calculation of ammonium ion concentration and of total ammonia concentration. In one embodiment, the electrodes and thermistor are simultaneously applied to a body fluid or tissue of a living animal and continuous data on ammonium ion concentration and total ammonia is produced. Alternatively, fluid samples can be withdrawn from an animal or person for similar measurements in vitro.

Abstract: A method and apparatus for measuring a gas partial pressure in a living body on the basis of the principle of polarography. A gas partial pressure sensor includes a biomedical electrode inserted in the living body. A temperature sensor is further provided to measure a temperature of the living body. A polarographic current value measured by the gas partial pressure sensor is corrected to a current value at a reference temperature depending on the temperature measured by the temperature sensor. Then the gas partial pressure at the reference temperature is determined based on a working curve which represents a relationship between the corrected polarographic current value and the gas partial pressure at the reference temperature.