Abstract: Provided is a method and metering system for the determination of active ions emitted from certain active substances such as rayon fibers containing fine particles of tourmaline known to exhibit permanent spontaneous polarization. The method comprises: continuously bringing air free from carbon dioxide as a carrier gas into contact with a bed of the active ion-emitting source material to carry off the active ions emitted therefrom; introducing the air after contact with the source material into distilled water; and measuring increase in the electric conductivity of the distilled water caused by the absorption of the active ions from the flow of the air as a carrier gas. The metering system comprises: a feed source of the non-ionic inert gas; a sample holder to contain the source material emitting active ions; a vessel containing distilled water to receive the air carrying the active ions; a means to determine the electric conductivity of the water; and pipelines connecting these parts for the flow of air.

Abstract: ECD with a non-radioactive electron source for generation of ions in a reaction chamber. The reaction chamber consists of two partial chambers, of which one is evacuated and contains the electron source, and the other contains connections for the feeding in of analysis gas as well as a collector electrode for detecting ions. The partition between the two partial chambers is permeable for electrons from the source but impermeable for gas molecules. The electron source may be a thermoemitter or a photocathode, which is irradiated from the outside through a window. In this way, contact between the analysis substance and the electron source is prevented, which increases measurement stability.

Abstract: The present invention discloses a novel method and apparatus for de-etching pin-holes in a passivation layer that is deposited over a metal conductor layer on the surface of a semiconductor wafer by utilizing a substantially clear, electrically conductive film as a top electrode immersed in an electrolyte for observing under an optical microscope bubbles generated from a pin-hole on the wafer surface which functions as a bottom electrode when a DC current is flowing through the top electrode, the electrolyte and the bottom electrode such that gases in the form of bubbles are generated at the pin-hole site where metal is exposed to the electrolyte.

Abstract: A sensor for measuring pH and conductivity for liquids is disclosed. The sensor includes a housing having a pH cell and a conductivity cell. A pH fluid flow path is defined between a pH cell fluid inlet and pH cell fluid outlet. An aperture within the pH cell is adapted to receive an electronic pH probe therein. The aperture is configured to position an end of the pH probe having a pH sensing area therein and juxtaposition to the pH fluid flow path so that fluid flowing within the flow path is exposed to the pH sensing area of the electronic pH sensor. A conductivity cell is adapted for placement of a conductivity sensor therein. The conductivity sensor is disposed between a conductivity cell fluid inlet and conductivity cell fluid outlet so that fluid flowing therethrough contacts the conductivity sensor.

Abstract: An apparatus is disclosed which is a microprocessor based instrument designed to conveniently and rapidly measure various analytes in environmental and biological samples. The instrument operates as a stand-alone unit powered by a battery or a DC power module and may be equipped with a communication port allowing uploading test results to a computer. Several unique electronic, microchip and software configurations were developed for the device to make it a portable, low-cost, safe, automated and simple-to-operate instrument particularly adapted for precise and accurate measurement of metal ions such as heavy metals such as lead in human blood.

Abstract: A testing device for qualitatively or quantitatively sensing an electrochemical or analogous reaction at the surface of a test strip (46), the current flowing or charge accumulated at the test strip being processed by electronics (50) to generate a current signal suitable for activating a display (52) typically in the form of a thermochromic layer.

Abstract: A method for determining the number of microorganisms in a liquid sample, including the steps of dividing the liquid sample into a plurality of separate sub-samples, measuring the magnitude of at least one impedance component across each of the sub-samples and determining the number of the sub-samples for which the measured magnitude of the at least one impedance component indicates microorganism growth. The method preferably further includes the steps of applying A.C. voltage at a plurality of frequencies across at least a portion of the sample and measuring the at least one impedance component in response to at least some of the plurality of A.C. frequencies.

Abstract: A materials characterization test cell is disclosed. The test cell includes a housing including spacers for supporting sample insulation materials, and a channel disposed in the housing to permit the passage of oil through the housing. A pair of electrodes is provided to provide a mechanism for making polarization spectrum and/or streaming electrification measurements.

Abstract: Methods and apparatus for detecting and utilizing a voltage produced by a variety of materials for process control and analysis purposes.

Abstract: A combination and unitary corrosion monitor and reference cell for cathodic protection systems includes an elongated tubular metal element of the same material as the structure to be protected and a reference cell on one end of the tubular element, adapted to be buried or submerged in an electrolyte. The tubular element includes resistance connections along its length and a reference resistance element sealed inside. Ratiometric resistance measurements enable the extent of corrosion and corrosion rates to be determined with automatic compensation for temperature changes. Both the resistance measurements and the potential measurements from the cell may be taken from the same test station or location.

Abstract: During voltammetric analysis of liquids, the indicator electrode must be frequently changed in order to prevent memory effects and resultant changes to basic conditions during measurement. In order to be able to change the indicator electrodes simply, a plurality of indicator electrodes are arranged on a common carrier. For accommodation of the liquid (2) to be analysed, a vessel (1) is provided and the carrier (5) is mounted to move in relation to this vessel (1) in such a way that one of the indicator electrodes (6) can be selectively brought into the area intended for the liquid. The reference electrode (8) necessary for the measurement is arranged in the vessel (1) and likewise connected with the measuring device (20). With that, changing of the selected electrode (6) ensues by moving the carrier (5) relative to said vessel (1).

Abstract: An apparatus and method for measuring conduction current through a sample portion of the surface of the solid conductor that is in contact with a liquid conductor, such as the solid electrolyte of a liquid-solid-liquid battery, is provided. The apparatus includes a probe having a hollow insulating probe body with an interior adapted for holding a small amount of the liquid conductor. The probe body insulates the probe liquid conductor from the surrounding liquid conductor and includes a tip having an opening in communication with the probe interior. The tip is adapted for making sealed contact with the solid conductor surface. The conduction current through the sample area can thereby be isolated and measured.

Abstract: A method for metering a reagent into a flowing medium includes adjusting a quantity of a reagent to be metered per unit of time into a flowing medium as a function of a thickness of a reaction zone in a catalytically active material. An apparatus for metering a reagent into a flowing medium includes a control unit, a device associated with the control unit for detecting a thickness of a reaction zone, and a metering device associated with the control unit for introducing a reagent into a flowing medium upstream of a catalytic converter as seen in flow direction of the medium. The control unit adjusts a quantity of the reagent to be metered into the flowing medium per unit of time by the metering device, as a function of a thickness of the reaction zone.

Abstract: The invention provides a compact device and simple method for circulating fluid over the surface of a membrane. The device comprises a housing that in combination with the surface of the membrane defines an enclosed volume through which the fluid is circulated. Some embodiments will include a membrane holding layer, a fluid dispersing layer, or both. The membrane holding layer has an opening through it to expose a predetermined surface area of the membrane to the fluid. The dispersing layer has a set of openings, typically slits, through the dispersing layer to disperse fluid over the surface of the membrane. Some embodiments may include electrodes for sensing or applying electrical potential to the membrane. A particularly preferred embodiment comprises a double sided device including a first housing, dispersing layer and membrane holding layer on one side of a membrane and a second housing dispersing layer and membrane holding layer on the other side of the membrane.

Abstract: The invention provides a compact device of simple construction for holding a membrane in contact with a pair of fluids, one on each side of the membrane. According to the invention, the membrane holder comprises a base and an upper cap, with the membrane held between them. Fluids may be circulated over the surfaces of the membrane. Electrode ports are provided through which electrodes may be placed in proximity to the membrane for measuring or applying electrical potential across the membrane. The membrane holder comprises a base, which includes a lower plate and a center plate secured thereto, and an upper cap, which screws into the base by means of a threaded connection between them. The upper cap may be sealed to provide an enclosed volume for holding one of the fluids or the upper cap may be open to provide an open reservoir for holding the fluid. One or more membrane holders according to the invention may be placed in and held by a specially constructed heater stand.

Abstract: A solid state, multi-use electrochemical sensor having an electrically nonconductive substrate, a working electrode, and a semi-permeable membrane covering the working electrode. The working electrode includes an electrically conductive material adhered to a portion of the substrate. A first portion of the conductive material is covered with an electrically insulating dielectric coating, and a second portion of the conductive material is covered with an active layer. The active layer includes a catalytically active quantity of an enzyme carried by platinized carbon powder particles, which are distributed throughout the active layer. A sensor package for incorporating a sensor is provided.

Abstract: A device or system for monitoring for the presence of leaks from a hazardous fluid is disclosed which uses two electrodes immersed in deionized water. A gas is passed through an enclosed space in which a hazardous fluid is contained. Any fumes, vapors, etc. escaping from the containment of the hazardous fluid in the enclosed space are entrained in the gas passing through the enclosed space and transported to a closed vessel containing deionized water and two electrodes partially immersed in the deionized water. The electrodes are connected in series with a power source and a signal, whereby when a sufficient number of ions enter the water from the gas being bubbled through it (indicative of a leak), the water will begin to conduct, thereby allowing current to flow through the water from one electrode to the other electrode to complete the circuit and activate the signal.

Abstract: A method and apparatus for simultaneously measuring the streaming potential of a fiber suspension and a filtrate thereof. A container is provided having an inlet and an outlet for the flow of fiber suspension therethrough, and a filter screen divides the container into an upstream compartment and a downstream compartment. Each compartment has an electrode pair disposed therein, each electrode pair including a cylindrical outer electrode configured for flow of fiber suspension therethrough and an inner electrode. Each electrode pair is connected to a differential amplifier, with the differential amplifiers connected to a microprocessor.

Abstract: A degradation level of transformer insulating oil can be checked by measuring leakage current of a sensor for measuring the degradation level of the insulating oil, in which DC power is applied to two electrodes of the sensor in the insulating oil for the transformer. In general, free carbons or nonsolute conductive particles are produced in the transformer insulating oil when used over long periods in the power transformer. The porous ceramic of the sensor for measuring degradation level of the insulating oil receives in the pores thereof the conductive impurity particles, and a conductive circuit is formed. Thus, this measurement for degradation level of insulating oil is based on the electric change states for the formation of the conductive circuit. Accordingly, by forming such structures, a method and apparatus for measuring degradation level of insulating oil by measuring leakage current of the sensor are provided.

Abstract: An apparatus for automated polyelectrolyte measurement in process materials comprises a sample vessel with an outer wall defining a cylindrical cavity and with a reservoir of larger diameter above and in communication with the cavity. A liner for the cavity and the reservoir are made of an electrically insulating material such as polytetrafluoroethylene. To clean the apparatus there is also provided an ultrasonic oscillator which is mechanically coupled to the sample vessel. In order to improve the cleaning process, the liner and preferably also the reservoir are attached to the outer wall in such a way as to resist tensile and shear forces and the ultrasonic oscillator is attached to the outer wall. Preferably, the liner is attached to the outer wall by an adhesive.

Abstract: In a cell for measuring electrical conductivity, a container (2) and electrodes (1) are made of ceramics having high corrosion-resistant property. Insulating ceramics are used for the container (2), and conductive ceramics having resistance value of several k .OMEGA..cm or less is used for the electrodes (1). The ceramics are far superior to glass in corrosion resistant property and mechanical strength under normal as well as high temperature conditions. Further, the cell is produced at lower cost than the one made of precious metal and has high corrosion resistant property and can be used under strong acid or strong alkaline conditions. It has high mechanical strength and can be used under high pressure and high temperature conditions and produced at low cost because precious metal is not used for the electrodes.

Abstract: An electrochemical test cell for measuring conductivity and transport properties of a solid or liquid electrolyte comprises a longitudinal chamber, produced, e.g., from a syringe, a pair of electrodes and means for holding the electrodes which defines an adjustable volume for containing the electrolyte and which aids in maintaining contact between the electrolyte and the electrode.

Abstract: A taste sensor has a lipid membrane including lipid molecules and a membrane-forming material for accommodating at least some of the lipid molecules on its surface. The lipid membrane induces a change in electrical characteristics, when a taste substance reacts with the surface of the lipid membrane. A signal processing unit receives a signal indicating a change in electrical characteristics induced by the taste sensor and generates data for determining the taste of the taste substance.

Abstract: An electric conductivity-measuring cell comprises a pressure container serving also as an outer electrode and provided with an inlet port of a liquid to be measured and an outlet port and an inner electrode provided within said pressure container so as to simplify it in construction and improve a measurement in accuracy.

Abstract: A cartridge-shaped reference element for potentiometric measuring systems exhibits a hollow body (20) as well as first and second sealed ends (30, 40) and a chamber (60). A silver electrode is provided as at least partial coating (50) of the inner surface of hollow body (20) bordering chamber (60), and coating (50) and protruding from chamber (60) so that a potential relating to the reference element can be measured.

Abstract: A process and an apparatus for monitoring the progress of haemodialysis by extra-corporeal measurement of the haematocrit are presented. The process comprises the steps of:calculating at a given time the variation of a function of the haematocrit over a short period, on the one hand, and over a medium period preceding this time, on the other,comparing the values of these variations,the result of this comparison is a first indicator of the progress of the haemodialysis.

Abstract: An apparatus for measuring the conductivity of an electrolyte comprises at least one conductivity cell, e.g., syringe-type conductivity cell and a constant temperature jacket. The syringe-type conductivity cell preferably employed in the apparatus comprises a generally longitudinal, cylindrical wall and two electrode rods which serve to define a volume for testing the conductivity of a sample in the volume. The constant temperature jacket comprises at least one longitudinal chamber for holding a conductivity cell, a temperature sensing device, and a fluid channel which is in fluid communication with a source of constant temperature fluid.

Abstract: Cell (19) for measuring moisture content of a material, comprising a sock (13) which is comprised of a plurality of braided threads, each thread consisting of a plurality of fibers comprised of an electrically non-conductive material. The sock is perfused with a moisture absorbing fluid. The sock comprises at least two electrodes (15, 17) in the form of wires comprised of a conducting material. These electrodes are braided as longitudinal threads in the sock (13). The electrodes are spaced from each other and extend essentially parallel to each other, the sock (13) being braided around a cylindrical core (11) comprised of an electrically non-conducting material. The axis of the core is essentially parallel to the electrodes (15, 17) and the threads in the sock (13) are permanently under tension to achieve contact between the threads and the electrodes (15, 17).

Abstract: In one embodiment, a thermal conductivity detector in a gas chromatograph is provided with a sensor connected in a resistive bridge with an alternating voltage applied to the bridge. Changes in thermal conductivity of a gas in the sensor cause changes in the temperature and resistance of the sensor which unbalances the bridge. A component of the voltage difference caused by the imbalance varies as the third harmonic of the applied voltage and has a magnitude related to the thermal conductivity of the gas. This third harmonic is measured to determine the thermal conductivity of the gas. In another embodiment, a sensor in a cavity through which gas flows is alternately operated at two different temperatures, and a difference in power required for operation is measured. The difference is independent of the temperature of the cavity walls and proportional to the thermal conductivity. This difference is measured to determine the thermal conductivity of the gas.

Abstract: A fluid contained in a vessel of multi-layer wall construction can intrude, because of damage or wear, through the inner containment layer and signal a problem with the life expectancy or safety of the vessel. By providing vessel walls having alternating layers of conductive material and non-conductive material, and by providing electrical connections for effecting circuitry to an instrument for measuring electrical properties across the inner containment layer, then intrusion of fluid into or through the inner wall can be detected by the instrument. For a conductive fluid, the inner layer of the vessel wall should be non-conductive and the layer covering that inner layer should be conductive. For a non-conductive fluid, the inner layer of the vessel wall should be conductive, and the layer covering that inner layer should be a non-conductive which is covered by another conductive layer. In many instances, it is preferred that the electrical property measured is the change in resistance, on the megohm scale.

Abstract: A system and method for detecting leaks in a storage tank that includes a stored tank liquid and an immiscible test liquid, and there is an interface formed between the tank liquid and the test liquid. The system includes a transducer and electronic device. The transducer further includes a measuring cell and a standard cell. The level of the interface within the standard cell does not change when the level of the interface changes. The level of the interface within the measuring cell changes according to the level of test liquid in the storage tank. The signal generated by the cells are processed by the electronic device to indicate whether there is leakage in the storage tank.

Abstract: A self-contained monitoring system for monitoring the operating condition of a fluid treatment device. A housing provides a pair of flow passages, one for liquid supplied to, and the other for liquid treated by the fluid treatment device. Separate pairs of electrodes are provided, with one pair of electrodes extending into one of the flow passages and the other pair extending into the other flow passage. The conductivities between each pair of electrodes are provided as signals to an electronic circuit contained within the housing which provides electrical output signals indicative of the operating condition of the fluid treatment device based upon the conductivity of the supplied and treated fluid flows.

Abstract: An improved detector assembly of an electro-magnetic conduction-type conductivity meter includes a plastic housing member having a liquid sample flow path extending therethrough. An excitation transformer is mounted in a cavity of the housing member along with the detection transformer for respectively inducing a current flow and detecting a current flow in the liquid sample flow path. A porous electrode is positioned adjacent one of the transformers and insulated by hydrophilic paper so that the entrance of any fluid within the cavity can be detected.

Abstract: The measurement of electrokinetic potential is of importance in paper-making. A measuring cell (12) for a specific potential known as streaming potential of the kind disclosed in EP B1 0 079 726 is now provided with measuring electrodes (40, 42) of a metal which forms a reversible electrochemical reaction with pure water to oxidize the metal. The electrodes (40, 42) used in the measurement mode in the cell have a film comprising an oxide of the metal electrochemically formed thereover. Such electrodes are found to give more stable and consistent measurement than the stainless steel electrodes used previously. Silver, lead, copper and alloys such as lead and silver are preferred. The measuring electrodes (40, 42) are regenerated within the cell (12) through electrochemical reduction to bare metal, followed by oxidation to re-form the film. This is performed with the aid of auxiliary electrodes (60, 62) in the cell. A control system (50) for the measurement and regeneration mode is described.

Abstract: A throughflow type mastitis detector having an inlet stub and an outlet stub by means of which the mastitis detector can be coupled to a milk tube; a measuring chamber having side walls, a closed bottom, and an opening opposite said bottom in spaced relationship to said inlet stub, through which opening the milk to be monitored, supplied through the inlet stub, can flow into the measuring chamber, and through which the milk can again leave the measuring chamber when the level of the milk within the measuring chamber exceeds the height of the lowest side wall portion; and a pair of electrodes in the bottom of said measuring chamber for measuring the electrical conductivity of the milk, characterized in that at least one of the electrodes has a convex head projecting above the bottom surface and a shank extending through an opening in the bottom.

Abstract: A conductivity sensor adapted for use in the conductimetric analysis of liquids includes a pair of conductivity electrodes incorporated into a conductivity cell assembly having a liquid flow control chamber, sensing chamber, and liquid exit chamber. Liquids to be measured are pumped into the liquid flow control chamber, where any turbulence in the liquid is dampened. The non-turbulent liquid is passed from the liquid flow control chamber to the sensing chamber, where the conductivity of the liquid is determined. The sensing chamber is adapted for changing the height of a column of liquid between the pair of conductivity electrodes in order to vary the cell constant of the sensor. The non-turbulent liquid is passed from the sensing chamber to the liquid exit chamber, where it exits the sensor. The sensor is well-suited for use in measuring conductivities of plating bath solutions and monitoring concentrations of major constituents of plating bath solutions.

Abstract: An improved detector assembly with an electromagnetic induction-type conductivity meter is provided with a pair of housing members forming a first liquid sample flow path at a central location, and a second liquid sample flow path on their outer circumference. An excitation coil and a detection coil extend about the first liquid sample path, while the second liquid sample flow path interconnects with the first liquid sample flow path both upstream and downstream of the respective coils. The second liquid sample flow path can substantially extend about the coils so that a relatively large induction current can be generated and measured as representative of the liquid sample.

Abstract: A thermal conductivity cell in the form of a bridge is used as one of the resistors in a Wheatstone bridge network. The output of the thermal conductivity cell is applied to the input of a low noise amplifier, the output of which is differentiated by an R-C coupling network having a time constant selected to pass a substantial portion of the output signal from the thermal conductivity cell with minimum attentuation. The R-C differentiating coupling network effectively reduces DC errors due to drift and offset and shapes the output signal improving the signal-to-noise ratio enabling trace amounts of materials to be analyzed.

Abstract: A sensor which may be immersed in a fluid to measure the pH and the ORP potential of the fluid is taught. The sensor has three solid state electrodes, a pH sensing electrode, a reference electrode and an ORP potential sensing electrode, which extend from a fluid-tight enclosure. The enclosure further contains a display means for indicating the pH measurement and the ORP potential measurement.

Abstract: A sensor mount is disclosed for use in a fluid volume measurement structure forming part of a fluid measurement system for feeding fluid in controlled amounts. The sensor mount includes a tubular body having first and second sensor mounting sockets whereby functionally different fluid sensors may be mounted to the tubular body. As fluid enters or exits the tubular body, a fluid sensor mounted in one or the other of the sensor sockets produces a signal to be used by a control portion of a fluid measurement system. The first sensor socket is provided as a through hole whereby a sensor may be mounted in fluid contact with the interior of the tubular body. The second sensor socket is provided as a blind hole for receiving a capacitance sensor out of fluid contact with fluids within the tubular body.

Abstract: A device for measuring ionic concentration in a sample liquid, having a detachable waterproof electrode housing. A body member has a computing device disposed therein and a display panel on an exterior surface. The waterproof electrode housing is demountably coupled to the body member. The electrode housing includes a flat surface sensor capable of measuring ionic concentration of the sample liquid when the device is placed on a flat surface, and is waterproof for measuring ionic concentration by immersion. A gap is formed between the body and the flat surface for preventing water from entering the body when the flat surface ionic concentration measurement procedure is being conducted.

Abstract: An apparatus and method for determining both the breakdown voltage and the conductivity of a particulate material, such as a developer material, is provided. In a preferred embodiment, the apparatus for determining breakdown voltage comprises a breakdown cell for storing a preselected quantity of the particulate material and a voltage breakdown ("VB") autometer, the VB autometer being adapted to apply a first voltage across at least portions of the preselected quantity of the particulate material. The VB autometer is capable of progressively varying the magnitude of the first voltage. A measuring circuit, for measuring a second voltage, is coupled to the voltage breakdown cell. When the second voltage substantially equals a preselected reference voltage, the first voltage substantially equals the breakdown voltage of the particulate material.

Abstract: A fuel sensor for sensing methanol in methanol-mixed fuel, which comprises a structure which defines a fuel passage through which the mixed fuel flows, an electrode assembly including a pair of probe portions which are exposed to the fuel passage, and an electric circuit causing the paired probe portions to exhibit positive and negative characteristics respectively in the mixed fuel. At least the positive probe portion is intimately covered with an electrically insulating film.

Abstract: An electrolytic conductivity detector cell featuring a flow bore for communicating gaseous products of a gas chromatographic system designed to provide electrolytic conductivity supporting compounds, combined with a liquid solvent in which the compounds in question dissolve. Electrodes are provided, in general, in the form of conducting pins which are positioned in bores in the cell block, intersecting the flow bore to expose surfaces of the electrodes to the fluids in the bore.

Abstract: An FET sensor apparatus comprising a sensor, a base member, and a support. The sensor comprises a semiconductor substrate having a predetermined crystal plane, a field-effect transistor formed on the semiconductor substrate, and a gate portion arranged on at least one of the major surfaces of the semiconductor substrate. The base member has a through hole in which the field-effect transistor is fitted. The support supports the sensor in the through hole in watertight fashion, with said gate portion exposed through an end of the hole.

Abstract: A conductivity meter usable in solutions where the path of the electric lines of force between two electrodes is altered. In one embodiment, detachable guard rings alter the path length based upon their own conductivity. In another embodiment, the physical distance between the electrodes is altered while maintaining a constant electrode configuration.

Abstract: A low pressure ion-chromatograph for the analysis of cations comprises eluent reservoirs, pump, sample injection valve, sampler, column, flow conductivity cell, electrical conductivity detector and recorder, wherein the pump is a low pressure electronic micropump, the angle included between the inlet and outlet of eluent in the cell is 45.degree.-135.degree., and the flow conductivity cell is oriented in such a position that the eluent inlet is either horizontal or sloping upwardly. There is no leakage in this instrument. No special demands are needed for seal and material. Very good precision and high sensitivity up to ppb level can be obtained, and with low cost.

Abstract: An electromagnetic conductivity meter comprises a core; a primary coil wound around the core; an alternating power source for applying an alternating voltage having a given frequency to the primary coil to excite the core; a tube wound around the core through which a liquid to be measured flows; induction current detecting means disposed at the opposite ends of tube; and an operational means for determining the conductivity of the liquid to be measured from a value of the induction current detected by the induction current detection means.

Abstract: A device for detecting relative differences in conductivity between filtered and unfiltered states of fluid comprises a differential comparator for measuring the voltage difference of its input ports, a differential bridge connected to the input sorts of the differential comparator for measuring the conductivity of the fluid, the differential bridge having electrodes for contacting the fluid in each of its filtered and unfiltered states and bridge adjustment circuitry for compensating for voltage offsets of the comparator and the bridge, and an indicator connected to the output of the comparator for generating an output indicative of the differential conductivity of the fluid in its filtered and unfiltered states.

Abstract: A pH-measuring system using a Barnacle electrode (e.g. Ni--NiO.sub.2) in an electrolyte to abstract hydrogen from a metal electrode in the same electrolyte, and produces data as to the time t.sub.max required for the current density at the exposed surface of the metal electrode to reach its maximum value j.sub.max after an external circuit between the two electrodes is closed. From t.sub.max and j.sub.max the pH in the bulk of the electrolytes is determined, for display or for control purposes.