Abstract: This invention presents a new packaging technique that allows for the use of a wider range of isolating materials for inductive conductivity sensors, thereby significantly reducing the cost of producing the sensors, improving their precision and accuracy, and increasing their sensitivity.

Abstract: The present specification discloses a dialysis system having a reservoir module with a reservoir housing defining an internal space, a surface located within the internal space for supporting a container that contains dialysate, and a conductivity sensor located within the internal space, where the conductivity sensor has a coil, a capacitor in electrical communication with the coil, and an energy source in electrical communication with the circuit.

Abstract: An arrangement (1) with an electronically commutated motor has an interface (10) for inputting analog setpoint signals (S) for the motor. The motor is powered, during operation, by an AC network via an electronic commutation system (20). The interface (10) is galvanically isolated from the electronic commutation system (20) by a galvanic isolation (30). Furthermore, for the transmission of an analog setpoint signal (S), a bitstream signal production device (2) is provided on the galvanically isolated interface side. Also provided is a transmission device (3), for transmitting the produced bitstream, as well as a signal-processing device (4). They are on the non-galvanically isolated side for the signal evaluation of the bitstream.

Abstract: The disclosure includes an inductive conductivity sensor for measuring the specific electrical conductivity of a medium with a transmitter coil energized by an input signal, a receiver coil coupled with the transmitter coil via the medium, which receiver coil supplies an output signal that is a measure for the conductivity of the medium, and a housing enclosing the transmitter coil and the receiver coil, which housing comprises at least one housing section designed to be immersed in the medium, the housing wall of said housing section surrounding the transmitter coil and the receiver coil. The housing is made of a magnetic plastic or resin for inductively decoupling the transmitter coil from the receiver coil. In certain embodiments, the housing may be made of a ferromagnetic material. Another aspect of the disclosure includes a method for manufacturing the conductivity sensor.

Abstract: A biosensor strip includes a strip body, a working electrode and a chemical reagent layer, wherein the strip body has a conductive portion and a reaction channel. The partial wall that forms the reaction channel is a partial or an entire surface layer of the conductive portion. The reaction channel has an opening that receives the sample fluid and an electrode hole. The working electrode is embedded in the electrode hole. The chemical reagent is configured in the reaction channel and generates an electrochemical reaction with the analyte. Therefore, after the sample fluid covers the reaction channel and the working electrode via the opening, the conductive portion and the working electrode on the wall of the reaction channel generate sensing currents and output the signals via the first and second signal output sides to determine an analyte concentration in the sample fluid.

Abstract: To an electrical characteristic measuring device that further improves the accuracy of measurement of an electrical characteristic of a blood sample. Provided is an electrical characteristic measuring device including: a measuring unit configured to measure an electrical characteristic of a blood sample; and an alert generation unit configured to issue an alert signal when an erythrocyte sedimentation rate in the blood sample exceeds a prescribed standard during measurement of the blood sample.

Abstract: An inductive conductivity sensor and a method for measuring specific electrical conductivity of a medium, comprising a transmitting coil fed by means of an input signal; coupled with the transmitting coil via the medium; a receiving coil, which delivers an output signal, which is a measure for the conductivity of the medium; and surrounding the transmitting coil and the receiving coil a housing, which has, intended for immersion in the medium, at least one housing section, whose housing wall surrounds the transmitting coil and the receiving coil. The housing section includes at least a first electrically conductive contact intended for contact with the medium and a second electrically conductive contact intended for contact with the medium.

Abstract: A device suitable for attachment to a milking platform at a “milking position” has a strippings viewing area and a light source, which is operable to illuminate in a suitable manner the strippings viewing area to enhance the visibility to an operator of any mastitis symptoms in use and/or to illuminate the udder to facilitate inspection or treatment. The light source may also be operable to give continuous or intermittent color signals to the operator and the device might also include an alpha-numeric area. The device might form part of a leg separator and/or sprayer and/or milk hose support. A milking platform with such a device is also claimed.

Abstract: A conductivity meter for measuring the conductivity of a fluid is provided. The conductivity meter has a cell circuit and a control unit circuit. The cell circuit has a square wave drive amp, a cell, and a trans-impedance amplifier. The fluid flows through the cell. The control unit circuit and the square wave drive amp are configured to apply a square wave pulse train having a voltage to the fluid of the cell, thereby inducing a flow of current through the fluid in the cell. The cell circuit trans-impedance amplifier and the control unit circuit are configured to obtain a plurality of measurements of current flowing through the fluid in the cell and estimate a raw conductivity of the fluid in the cell using the current flow measurements. A method for measuring the conductivity of a fluid is also provided.

Abstract: An exemplary method for measuring the electrical resistance and/or electrical conductivity of solutions, includes: exciting the electrodes with a rectangular shaped, alternating current of a certain frequency fH through a connecting cable; synchronously rectifying a voltage of the electrodes of the measuring cell in response to the alternating current, calculating a first average voltage, dividing the first average voltage by the current amplitude to obtain a first impedance RH; then exciting the electrodes with a rectangular shaped, alternating current of another frequency fL through the connecting cable; synchronously rectifying the voltage of the electrodes in response to the alternating current, calculating a second average voltage, and dividing the second average voltage by the current amplitude to obtain a second impedance RL.

Abstract: A system and method for controlling a power storage device through the Stimulation and Intensification of Interfacial Processes (SIIP) is provided. A signal generator can provide a low voltage sinusoidal AC signal across a battery terminal, or other reactor vessel, during charging and discharging states. For example, the battery/reactor vessel can be of Li-ion and NiMH designs, a fuel cell, a Zn—O cell, or other devices that have features of rechargeable batteries. The output of the signal generator (i.e., voltage, wave type, and frequency) can be controlled based on battery parameters (e.g., internal resistance, output power, temperature). The internal resistance of the battery can be reduced, and the discharge time can be increased. Elastic waves can also be provided to a battery/reactor vessel to stimulate the interfacial processes. The signal generator can be an integrated circuit which is packaged with the battery and can be powered by the battery.

Abstract: A liquid concentration measuring device has first and second switches, which are turned on and off at two frequencies. When the first switch is turned on and the second switch is turned off, a detection electrode pair is charged. When the first switch is turned off and the second switch is turned on, the positive side of the detection electrode pair is grounded so that the charged detection electrode pair discharges. The difference between the output voltages of an amplifier produced by charging and discharging the detection electrode pair at the two frequencies is used to determine an alcohol concentration in gasoline.

Abstract: The invention relates to a method of measuring the conductivity of a pure or ultrapure liquid, notably water, using electrodes, characterized in that it consists in determining the conductivity by modeling the liquid in the form of an equivalent electrical circuit diagram comprising a resistor R, a capacitor Cp in parallel with the resistor R, and a series capacitor Cs. It also relates to a device for implementing this method and a purification system incorporating such a device.

Abstract: Apparatus and methods are disclosed for obtaining an image of the impedance properties of an object by inferring a measure of straight-line path impedance along a plurality of paths from a plurality of current amplitude and phase measurements made between combinations of electrodes placed at selected points, and/or from measurements of the intensity of the electromagnetic signal emitted when an alternating current is made to resonate along the straight line path.

Abstract: Disposable, pre-sterilized, and pre-calibrated, pre-validated conductivity sensors are provided. These sensors are designed to store sensor-specific information, such as calibration and production information, in a non-volatile memory chip on the sensor on in a barcode printed on the sensor. The sensors are calibrated using 0.100 molar potassium chloride (KCl) solutions at 25 degrees Celsius. These sensors may be utilize with in-line systems, closed fluid circuits, bioprocessing systems, or systems which require an aseptic environment while avoiding or reducing cleaning procedures and quality assurance variances.

Abstract: A system and related method are provided to calibrate for wire capacitance during use to minimize error in conductivity measurement of the target fluid. The system includes a signal generator configured to drive the conductivity cell and the temperature element, with an alternating current (AC) drive signal having variable parameter. The system further includes a processor assembly electrically coupled to the conductivity cell and the temperature element to calculate a conductivity value of the fluid. The conductivity value is a function of the values of the temperature measurement, the compensation measurement, and the raw conductivity measurement, thereby compensating the conductivity value for capacitance effects. In this manner, the system effectively compensates for capacitance attributable to wiring extending between the electrode and other electronics of the sensor, usable with wiring of varied and unknown lengths.

Abstract: A measuring circuit is provided for a memory integrated within a semiconductor device. The measuring circuit includes initializing means and an oscillating loop. The initializing means loadings two complementary values into at least two locations of the memory. The two locations are addressed by a first address and a second address. The oscillating loop comprises a logic circuit for alternatively generating the first address and the second address from data read from the memory so as to successively read data from the first and second memory locations to produce an oscillating signal that has a frequency that depends on internal parameters of the memory. Also provided is a method for qualifying a memory by initializing the memory by loading two complementary values into two locations, and generating an oscillating signal with a frequency that is dependent on internal parameters of the memory.

Abstract: A method and apparatus for measuring a predetermined parameter, by providing a displaceable sensor on a mounting member such that the displaceable sensor changes in location, form or length with respect to the mounting member in accordance with the predetermined parameter. A cyclically-repeating energy wave is transmitted to or through the displaceable sensor, and a predetermined fiducial point in the received cyclically-repeating energy wave is detected and used for continuously changing the frequency of the transmitted cyclically-repeating energy wave such that the number of waves received is a whole integer. The change in frequency is used to produce a measurement of the predetermined parameter. Several embodiments are described wherein the displaceable sensor is a deformable membrane, an end wall of a bellows, a spring-mounted member, a displaceable plunger, and a bar changing its length in accordance with the parameter to be measured.

Abstract: A system for electrostatically measuring the shape or pattern of objects including an array of sensor devices having the capability of responding, due to variable electrostatic coupling, to produce differentiated output signals when a sensor element forming part of each device is present and when it is not.

Abstract: Various circuit configurations for use in switch assembly used in a surgical hand piece system are provided. The circuit configuration provide a number of functions such as permitting the presence and direction of conductivity to be detected. The circuit configurations also provide a way to detect and measure the degree of influence of debris which is located between the conductive members of the handpiece. In addition, the circuit configurations also provide a way to identify the type of switch end cap which is attached to the handpiece. The handpiece body and the switch mechanism are electrically connected to one another in such a manner that permits the switch end cap to be freely rotated about the handpiece body and reduces the number of conductive members needed to communicate the status of each switch.

Abstract: Two conductivity measuring cells each having at least two electrodes are arranged in series in a flow path of a sample to be measured so that the sample may make contact with the cells in sequence. A difference conductivity meter produces the difference between the signals themselves detected by the conductivity cells as the difference in conductivity of the sample between the positions of the conductivity measuring cells. Based on the predetermined correlation between the change in conductivity of the sample and the change in concentration of the ion of interest in the sample, an ion concentration meter thus constructed derives the change in ion concentration of the sample from the output from the difference conductivity meter. The ion concentration meter can measure a minute change in ion concentration, such as of ammonia, with extremely high accuracy and sensitivity, while carrying out continuous measurement.

Abstract: A inductive conductivity sensor for measuring conductivity of a fluid includes a housing supporting a controlled impedance loop and a transducer. The transducer includes a driver for inducing a first current into the fluid adjacent the housing, and for inducing a second current into the controlled impedance loop. The transducer further includes a detector for inductively measuring the first and second currents.

Abstract: Liquid conductivity and temperature are measured in respective sensitivity fields that are collocated—i. e., in volumes that nearly match by mathematical, geometrical, or functional criteria. Collocation is as distinct from mere adjacency or proximity; and is with respect to measurement volumes, not measuring hardware. Preferably pressure too is measured with sensitivity very generally collocated to the conductivity and temperature sensitivity. Preferably, respective temporal/spatial bandwidths of the two (or three) sensors are matched. Preferably the pressure sensor is a MEMS transducer, the conductivity sensor is a four-terminal device, the thermometer is a thermistor encapsulated in a silkscreened glass wall, and circuits (1) compensate for time lag between conductivity and temperature measurement, (2) remove artifacts due to detritus in or near either sensor, and (3) derive secondary parameters of the liquid.

Abstract: An improved apparatus for measuring conductivity or resistivity compensates for series capacitance and parallel capacitance. A sine wave excitation potential is applied to the series combination of a reference resistance and a conductivity cell. The voltages across the reference resistance and the cell are sampled. To compensate for series capacitance, both sampled voltages are synchronously rectified with respect to the phase of the sampled reference resistance voltage. To compensate for parallel capacitance, both sampled voltages are synchronously rectified with respect to the phase of the sampled cell voltage. The rectified voltages are integrated and the cell conductivity or resistivity is calculated from the product of the reference resistance and the ratio of the integrated voltages.

Abstract: Molding compositions including polyhydroxyalkanoates are provided. The use of polyhydroxyalkanoates as a binder in molding compositions provides improved binder removal in the finished molded product, and offers a wide range of physical properties suitable for use in a variety of processing conditions. The composition preferably includes a powdered material, such as a metal powder, ceramic powder, or blend, admixed with a polyhydroxyalkanoate binder. The compositions are useful in powder processing techniques, such as injection molding, slip casting, tape casting, or extrusion.

Abstract: A liquid conductivity measurement system is disclosed that accurately measures a liquid's conductivity over a range spanning at least several orders of magnitude using just a single sensor, but minimizing the adverse effects of capacitive and other non-linear factors on the conductivity measurement. The system includes a sensor having two spaced-apart electrodes immersed in the liquid and a drive signal source that applies to the sensor an ac electrical signal having a selected frequency and predetermined magnitude. A voltage detector monitors a sensor voltage signal across the sensor's two electrodes and produces a measurement of the liquid's conductivity. The drive signal source is configured to iteratively adjust the frequency of the ac electrical signal based on the sensor voltage signal, to optimize the liquid's conductivity measurement.

Abstract: The present invention provides an aqueous gel comprising a polymer of (meth)acrylamide or particular (meth)acrylamide derivative(s), particulate metal oxide(s) and an aqueous medium, a process for producing said gel, and products utilizing said gel.This aqueous gel can be produced so as to have transparency, has fire resistance and can prevent the spreading of flames, and is highly elastic. The aqueous gel, when produced as a transparent gel, becomes cloudy when heated or cooled and is useful for the shielding of heat rays or cold radiation.

Abstract: The present invention relates to a method for measuring conductivity, in particular for use in liquid chromatography systems, and to a device for performing such measurement. In one aspect it provides a method of measuring conductivity in liquids, comprising applying an AC voltage over a conductivity measurement cell. In response to a conductance value calculated from the output of the cell, an expected frequency of the AC voltage is generated. The AC voltage frequency is set to the calculated value. The above steps are repeated until two consecutive conductance determinations differ by only a predetermined absolute value. Then the value may be displayed and registered as the true conductance value of the sample.

Abstract: An apparatus for the registration of the humidity and acid content of a refrigerant or another non-polar liquid including a capacitive sensing element placed in the refrigerant or liquid and connected to an electrical evaluation circuit, the electrodes of the capacitive sensing element being formed of two different metals having different normal potentials, and the electrical circuit includes circuit elements for determining the resistive loss in the capacitive sensing element and circuit breakers for determining the current delivered by the sensing element.

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: Improved circuits for measuring the conductivity of a solution confined between two electrodes in a cell compensate for series capacitance and parallel capacitance between the electrodes. A bipolar square-wave signal is applied to the cell. In one embodiment, the current through the cell is measured by an op-amp in current-to-voltage converter configuration. A feedback resistance employed with the op-amp in a feedback loop is controlled to a low value to ensure that the parallel capacitance is fully charged during an initial portion of each half-cycle of the drive signal. The feedback resistance is then selected so that the gain of the feedback loop is responsive to the range of the resistivity of the solution, and the measurement is made.

Abstract: A liquid mixing ratio detecting apparatus is designed so that an oscillation voltage generated by an oscillation unit is applied to one of a differentiating circuit and an integrating circuit, which is constituted by a combination of a capacitor composed of a pair of opposite electrodes for detecting a mixing ratio of a mixed liquid and a resistor, and a mixing ratio detecting unit produces a signal relating to an inclination rate of one of a differential waveform signal and an integration waveform signal, which is generated by one of the differentiating circuit and the integrating circuit, respectively, thereby obtaining a signal representing the mixing ratio of the mixed liquid on the basis of the produced signal relating to the inclination rate of the waveform signal.

Abstract: Improved circuits for measuring the conductivity of a solution confined between two electrodes in a cell compensate for series capacitance and parallel capacitance between the electrodes. A bipolar square-wave signal is applied to the cell. In one embodiment, the current through the cell is measured by an op-amp in current-to-voltage converter configuration. A feedback resistance employed with the op-amp in a feedback loop is controlled to a low value to ensure that the parallel capacitance is fully charged during an initial portion of each half-cycle of the drive signal. The feedback resistance is then selected so that the gain of the feedback loop is responsive to the range of the resistivity of the solution, and the measurement is made. The period of the bipolar signal is selected responsive to the selected loop gain, to ensure that a filter capacitor across the op-amp is fully charged, and to limit distortion caused by the series capacitance.

Abstract: Apparatus for measuring the electrical impedance of low conductivity samples, and particularly microbial suspensions, has a coil surrounding a tubular sample container. A capacitive pick-up on the sample wall provides an input to a variable gain amplifier driving the coil. The resident frequency of the circuit is measured to provide an indication of sample conductivity.

Abstract: A navigation system for an aircraft fitted with an autopilot, the system comprising at least one ground-based transmitter (2), receiver means (7,8) mounted in the aircraft and including two antenna (5,6) oriented such that their polar diagrams overlap and are inclined with respect to the fore-and-aft axis of the aircraft.

Abstract: The invention provides an apparatus for controlling both the supersaturation of the mother liquor and the crystal content of massecuite by measuring di-electric constant and electrical conductivity at radio frequencies by means of a probe which is included in a circuit which may be tuned to a fixed setting or may be variably tuned, the combined impedance is measured as a function of the tuning and the measurements are compared with predetermined desired values. By suitable combination of the two signals, measurement of crystal content and mother liquor supersaturation can be controlled.

Abstract: An analog ASIC (Application Specific Integrated Circuit) circuit has a power control section, a conductivity filter testing section, a light emitting diode (LED) driving section, and a bias section. The LED driving section is responsive to the conductivity filter testing section for indicating when the filter should be replaced. The power control section, conductivity filter testing section, LED driving section, and bias section are all operated in a controlled timed relation by a digital ASIC logic system to minimize power use.

Abstract: An automatic monitor for potable water quality which monitors total dissolved solids (TDS) in drinking water. Built into a faucet base are a pair of indicators in the form of one green and one red LED. A sensor in the form of a pair of spaced electrodes extends into the supply conduit for the faucet and measures the electrical resistances of the water in the conduit. A pulse power source powered by a battery supplies power to automatically periodically power the sensor and illuminate the green LED as long as the TDS level is below a preselected value. If the level exceeds the preselected value, the red LED is periodically illuminated. The duty cycle for operation and illuminating the LEDs is approximately 0.5% whereby battery drain is sufficiently low that months of continuous monitoring is possible using 4 AA batteries. No ON-OFF switch is needed. If neither LED illuminates once every two minutes, the batteries need replacement.

Abstract: An apparatus and method are provided for reducing the effects that common mode currents and/or voltages have on the measurements made by instrumentation that senses physical phenomena. The apparatus includes a cell having a first sensor, a second sensor and a passageway for containing the fluid to be measured. The cell, sensors and passageway are symmetrically disposed about an axis. Due to this symmetry, a ground can be located at the axis of symmetry. The apparatus also includes first and second measuring circuits associated, respectively, with the first and second sensors. The first measuring circuit produces a signal respresentative of the measured parameter between the ground and the first sensor. The second measuring circuit provides a like function for the second sensor. The signals produced by the first and second measuring circuits are summed by a potentiometer.

Abstract: A liquid conductivity sensor which features simply and inexpensively driving the excitation transformer of a two-transformer/fluid-loop remote conductivity sensor with a square wave excitation signal provided by a digital timer and a flip-flop. Also disclosed is using an electrodeless conductivity sensor to sense conductivity of dialysate.

Abstract: Improved accuracy in solution conductivity or resistivity measurment uses a center-sampling technique in which an AC drive is applied to a conductivity cell and the conductivity cell voltage is sampled during a predetermined time interval in the center of a half cycle drive waveform. The effects of cell capacitance, and particularly the electrode-solution capacitive, are compensated by periodically sampling during a second time interval which is different from the first interval. Based upon the difference between the sampled voltages in the first and second intervals, a correction to the measured conductivity or resistivity is made to compensate for capacitance induced errors.

Abstract: A system for monitoring the operation of a water purification system of the type having an inline membrane includes a first conductivity measurement cell located upline of the membrane and a second conductivity measurement cell located downline of the membrane. The cells are electrically connected in series and across the output of a symmetrical square wave generator. A differential amplifier compares the voltage across one of the cells with a predetermined reference voltage to develop a control signal when the conductivity of downline cell relative to the upline cell rises above a predetermined threshold level. An output circuit responsive to this signal drives an appropriate one of two indicator lamps to indicate satisfactory or unsatisfactory system operation.

Abstract: A cell for remotely sensing conductivity of a fluid passing through it, the cell having an inlet and an outlet and two fluid paths between the two, thereby defining a fluid loop, an excitation transformer comprising a first toroidal core having a hole through it and wire turns around it, the core encompassing a portion of the fluid loop therein, and a sensing transformer comprising a second toroidal core having a hole through it and wire turns around it, the core encompassing a portion of the fluid loop, the cores being coplanar to thereby reduce leakage between the transformers.

Abstract: A contamination monitoring system is disclosed wherein a low frequency alternating current signal is applied to a remotely mounted probe in the liquid being monitored for contamination. A fixed resistor located at the probe is electrically in parallel with the resistance of the liquid being monitored. The resistor is isolated from the liquid and allows a signal to be transmitted through an interconnecting cable even though the liquid resistance is very high. A signal is returned to signal processing electronics via the interconnecting cable to a high input impedance amplifier which drives an isolation transformer.

Abstract: A circuit for measurement of the conductance of an electrolyte cell is disclosed which features compensation for non-linearities produced by resistance in series with the resistance of the cell and for non-linearities caused by polarization of the cell due to chemical, kinetic or other effects within the cell. The cell is driven by an AC signal, and the circuit features a feedback loop in which a portion of the AC output signal is fed back for compensation of the series resistance and in which an op-amp generates a compensating DC voltage, both of which are summed with the AC excitation signal prior to its being supplied to the cell.

Abstract: An instrument for measuring electrical conductivity of a liquid comprises a two-electrode probe for insertion into the liquid. A triangular waveform generator (IC4 and IC5) impresses a voltage of fixed amplitude on one electrode of the probe by means of driver circuitry (IC3). This voltage drives an electric current through the liquid to the other electrode of the probe. Receiver circuitry (IC6) detects the current at this other electrode, and converts the detected current to a triangular wavefore AC voltage signal. Amplifier circuitry (IC1) amplifies the output of the receiver circuitry, and the amplified voltage signal is converted to a smoothed DC voltage signal by precision rectifier circuitry (IC2 and IC7). The output of the precision rectifier circuitry is processed to obtain a signal indicative of electrical conductivity of the liquid.

Abstract: The new instrument for taking readings of the hematocrit value from a blood sample has two electrodes with which the conductivity of the sample may be measured. The sample contacting faces of the electrodes are placed in a horizontal plane with an accurately fixed spacing therebetween so that a blood column of a given size may be formed from the sample. The sample is acted upon by ac. From a reading representative of the change in impedance the hematocrit value may be read off from a calibration curve.

Abstract: A high permeability ferrite core, which includes a gap between adjacent ends thereof, is combined with a magnetic coil encircling the core, and is located in a sub positioned in the drill string just above the drill bit of a borehole drilling rig. The core is positioned so that the gap thereof lies across a recess region formed in the outer wall of the sub. Drilling fluids flow along the outer surface of the sub on the return path from the drill bit to the mud pits located at the surface of the borehole. A constant current, or voltage, at a frequency within the range of 20 KHz-20 MHz is applied to the terminals of the coil encircling the core and the eddy currents developed in the gap region produce a measurable back emf at the coil terminals. The current produced by this emf voltage is indicative of the resistivity of the drilling fluid within the recess region in the wall of the sub and the fluctuations of the voltage accurately follow the variations in drilling fluid resistivity.

Abstract: The intrinsic time constant .tau. of liquids is measured directly by using he apparatus of the present invention termed a "taumeter". The taumeter impresses a predetermined voltage, level between a pair of electrode immersed in the liquid to be measured. The taumeter then measures the time it takes for the foregoing voltage to decay from a predetermined value V.sub.A to a predetermined value V.sub.B. Comparator logic produces a gate pulse having a leading edge at a time T.sub.A corresponding to the occurrance of the predetermined voltage V.sub.A and a trailing edge at a time T.sub.B corresponding to the occurrance of the predetermined voltage V.sub.B. The gate pulse is used to gate a system counter which counts the zero crossings of a very accurate system clock to determine the intrinsic time constant of the liquid. The foregoing pulsing is repeated as determined by a duty cycle generator.

Abstract: A method of measuring the impedance of a sensor by applying a sine-shaped AC voltage and transforming the response signal proportional to said impedance into a DC voltage such that even for very little measured voltage highest linearity is present. The method comprises the steps of generating a square wave voltage together and in synchronism with said AC voltage, applying said AC voltage to said sensor impedance, filtering the resulting AC voltage and bringing it into a defined phase relation to the square wave and rectifying the AC voltage by means of a switch controlled by said square wave. The rectifier circuit is a low-pass circuit having a grounded resistor which by said switch intermittedly is short-circuited.