Abstract: A conductivity measuring device for measuring the electric conductivity of iquids has a current source device with current electrodes connectable thereto, via which a current can be fed into the liquid, and a measuring circuit connected to two voltage electrodes.In order to reduce measuring errors on account of polarization effects, the current source device in accordance with the invention, generates the current having the rectangular waveform, wherein the measuring circuit is implemented as switched capacitor circuit comprising a measuring capacitor being connectable to and disconnectable from the voltage electrodes via a switch arrangement in time dependency of the path of the current having the rectangular waveform.

Abstract: A method and apparatus is provided for monitoring and locating the presence of fluids leaking from a containment vessel. A multiplicity of probes having conductive affinity are strategically oriented adjacent the containment vessel and periodic surveillance is made relying on conductivity of the sub-surface media within which the probes have been placed, such that disturbances in the conductivity correlate with migration of the leaking fluid. The method and apparatus may be utilized to detect migration of salinated fluids into a region where previously less salination existed. The probes can be oriented adjacent a surface and yet determine a conductivity of the sub-surface media at a plurality of different pseudo-points having varying depths. The presence, location and extent of a leak can thus be monitored.

Abstract: The present invention concerns a measuring device, notably for measuring the level of glucose in blood, intended to be used with a removable sensor comprising at least one active zone. In particular, the invention concerns the electrical connection between the measuring device and the removable sensor. Each electrical contact surface of the removable sensor is connected to two electrical contact organs to enable the condition of the electrical contacts between these electrical contact organs and the corresponding contact surfaces to be checked before a measurement is carried out.

Abstract: Photoresponsive devices including a photoresponsive electrode are provided, and methods for their use to measure changes in environment at a site at or about the surface of the photoresponsive device. By employing a source of light for irradiating a site on the surface and means for biasing the photoresponsive electrode in relation to a counterelectrode, a variation in electrical signal can be related to a change in a medium in photoresponsive modulation relationship to the photoresponsive electrode surface.

Abstract: A test fixture is provided for testing the resistance associated with contamination material on the surface of electrical contacts mounted to a printed circuit board. A probe used to engage the contacts consists of first and second conductive probe segments which form a sandwich about a layer of insulating material. A current source provides a constant alternating current which is applied across the first and second probe segments. Circuitry is provided for amplifying the alternating current voltage developed across the first and second probe segments in response to the constant current. Circuitry is provided for rectifying the amplified alternating current voltage to provide a direct current voltage which is proportional to the measured resistance of the contact engaged by the probe. Data corresponding to the bulk and contact resistance associated with the clean contact is stored in memory of a computer.

Abstract: Apparatus and method for determining the amount of oxidative and hydrolytic degradation in the surface of a highly resistive material, such as a polymer. A special probe provides an annular resistance on the surface of a sample of the material. The voltage drop across the sample determines the input to a meter circuit. A guard circuit has an applied voltage that is substantially the same as the voltage at the meter circuit input. This circuitry permits a very low voltage source to be used.

Abstract: A method and system for rapidly connecting and rapidly disconnecting a large number of point contacts onto a pipe surface for detecting defects in pipe and other structures is taught. The method and system involve independently pressing a plurality of sharply pointed pin contacts onto the pipe surface by a means, such as a spring. The system comprises a plurality of electrodes each having a plurality of pins, as illustrated seventeen (17) pins, arranged in a pattern. Each of the plurality of pins is held in a conforming opening in the electrode and is urged by springs means, such as a coil spring, against the surface of the structures. Each of the plurality of pins (sixteen (16) current pins and one voltage pin) are individually connected to a power supply and sensing apparatus. This system and method has proved operable for detecting defects in structures, such as pipe.

Abstract: A device for sensing the occurrence of destructive events and events involving mechanical shock in a non-intrusive manner. A pair of electrodes is disposed in a parallel configuration on a backing strip of flexible film. Electrical circuitry is used to sense the time at which an event causes electrical continuity between the electrodes or, with a sensor configuration where the electrodes are shorted together, to sense the time at which electrical continuity is lost.

Abstract: Amounts of electric charges in a semiconductor wafer are measured by using a non-destructive measuring device. First and second flat-band voltages before and after a specific charging process are measured with a non-destructive C-V measurement device. A gap between a test electrode and a surface of a semiconductor wafer is also measured before and after performing the charging process. The electric charge accumulated proximate the surface of the semiconductor wafer is determined according to measured values of the gap and the flat-band voltages before and after performing the charging process.

Abstract: A method for measuring the current flowing through a cow is disclosed. The method uses a four-terminal resistor precision measurement technique to accurately measure the electric current flowing through a cow as a result of voltages found on dairy farms. The four-terminal resistor technique allows the present invention to measure the current without the need to account for unpredictable environmental conditions on the dairy farm that may effect electrical contact resistances. The present invention uses Ohm's Law to determine current by dividing the voltage drop across a conductive path in the cow by the resistance of the conductive path. The elements utilized do not restrict cow movements and allow the cow to move about freely so as to enable dairy farmers to monitor conveniently and continuously for electric currents resulting from stray voltages on the dairy farm without interfering with daily farm activity.

Abstract: An impedance meter is not adversely affected by errors originating from changes in characteristics of measurement cables under measurement conditions such as in an environmental test wherein an element to be measured is remote and high and wide measurement frequencies are used. The voltage and the current of an element to be measured are measured to obtain its impedance and the like. A circuit configuration is provided wherein a cable for supplying a measurement signal to the element to be measured and for detecting the current flowing through the element to be measured is a triaxial cable and a cable for detecting the voltage is a coaxial cable, and wherein impedance matching is performed at the ends of the triaxial cable and the coaxial cable on the side of a measuring device and a balun is provided to float an ammeter on a coaxial cable connecting the ammeter-side end of the triaxial cable to the ammeter.

Abstract: An inflatable restraint system includes a diagnostic circuit which measures the resistance of an external deployment path containing a squib. The circuit supplies a test current through the path and measures the voltage across the path which is monitored by a microprocessor. A vehicle battery supplies the power to the system and is connected to a constant current source in series with the external path to provide the test current. A current limiting device between the external circuit and ground comprises a current sink allowing a maximum safe current in the external circuit in the event of inadvertent application of battery voltage to the external circuit and, during a normal resistance test, imposes only a small voltage drop on the test current circuit.

Abstract: A method and apparatus for determining the resistance of the coils and commutator connections in an armature of an electric motor wherein a current is generated between a first commutator segment and a commutator segment located at least three segments beyond said first segment, a first voltage is measured across the first commutator segment and an adjacent second commutator segment, a second voltage is measured across the second commutator segment and an adjacent third commutator segment, and a third voltage is measured across a pair of commutator segments which are adjacent to the first commutator segment. After the three voltages are measured, the current is disconnected, and a voltage is generated across two commutator segments spaced at least three segments beyond the first segment. The generated voltage is adjusted so that the voltage measured across the second and third commutator segments equals the previous measurement, and the voltages are remeasured.

Abstract: With a view to enabling errors in the space potential to be automatically corrected by detecting a floating potential in each of a plurality of probes and to remove the errors in measurement based on the corrected space potential to thereby realize the accurate measurement of the space potential, there is provided a triple-probe plasma measuring apparatus, which comprises: a circuit for measuring electron temperature and electron density of a plasma with use of triple probes; a circuit for detecting and holding a floating potential difference; a differential voltage adding circuit; a fixed voltage source; and a change-over switch, the apparatus being capable of determining a difference in the floating potentials at the position of said probes, and superimposing the potential difference determined on the fixed voltage.

Abstract: A MIS diode sensor having a Pd/Cu alloy electrode is sensitive to and can detect CO, H.sub.2, C.sub.2 H.sub.2 and C.sub.2 H.sub.4. An array of MIS diode sensors having varying electrode compositions can indicate a fault in an electrical transformer by the detection of at least one of the key fault gases CO, H.sub.2, C.sub.2 H.sub.2 and C.sub.2 H.sub.4.

Abstract: An E-field sensing apparatus detects the energization of high voltage utility transmission and distribution lines. An external housing substantially shields internal components of the apparatus from the detected E-field. A conductive wire extends from the housing where it is exposed to the E-field. A signal is induced onto the exposed wire and sensed by the apparatus. The length of exposed wire and the distance of the apparatus from the high voltage line attenuate the E-field so the induced signal is within operational parameters of internal sensing components. Adjustments to the wire length and apparatus distance enable detection of E-fields surrounding power lines carrying voltage levels of a predetermined voltage level (i.e. approximately 2000 volts and higher). In response to the E-field the apparatus generates an analog output signal and a line isolation control (one-bit digital) signal. The analog output signal drives a meter, LED or other indicating device serving to aid maintenance engineers.

Abstract: A system 20 for measuring the sheet resistance of a conductive layer on the top surface of a semiconductor wafer 22 is disclosed herein. In one embodiment, the system includes a chuck 30 electrically coupled to the backside surface of the wafer 22. The chuck 30 is capable of supporting the wafer 22 electrostatically. A signal source 40 provides an excitation signal to the wafer 22 and circuitry for monitoring an induced signal is provided. The sheet resistance on the top surface of the wafer 22 is determined from the measurements of the excitation and induced electrical signals. Other systems and methods are also disclosed.

Abstract: An oxygen sensor is based on a thin film of a compound oxide supported on a substrate such as quartz. The compound oxide has a general formula ABO.sub.2.5+x, where A is an element of the lanthanum family, alkaline earth metal or their mixture, and B is a transition metal or a mixture of transition metals. X is a variable number, changing from about 0 to about 0.5 between the reversible oxygen-deplete and oxygen-rich forms of the oxide. In an elevated temperature and oxygen-containing atmosphere, the thin film can undergo reversible bulk oxidation resulting in a detectable change of its physical properties such as mass, optical transmissivity and electrical resistance.

Abstract: This invention embodies a method and apparatus for determination of surface resistivity (.rho.) of materials to be used for a desired purpose. The surface resistivity is obtained by measuring surface resistance (R) of at least one square area of the material, and converting the surface resistance into a surface resistivity (.rho.) by a correction factor K (K=.rho./R) whenever the total area of the material is greater than three square area. The surface resistance is measured by placing a pair of square electrodes, spaced from each other a distance equal to the side of the square, applying measuring voltage potential to the electrodes, and determining the surface resistance of said at least one square area. The surface resistivity of materials of any size can be obtained by multiplying the surface resistance value by a correction factor determined for the size of the material being investigated.

Abstract: Gate oxide on a semiconductor wafer is effectively stressed on a per-wafer basis during fabrication. Because it was effectively stressed, gross testing the gate oxide after device fabrication provides a good indication whether a completed MOS device will be subject to infant mortality. After the gate oxide is formed, a source of overvoltage may be coupled between the raw oxide and the underside of the wafer, to accelerate stress due to defects in the oxide. Alternatively, the oxide may be stressed after deposition of the gate material by coupling a source of overvoltage directly to the gate material and to a probe on the underside of the wafer. The oxide may also be stressed after patterning and definition of the gate material by coupling a source of over-voltage to all of the gates simultaneously, preferably using a mercury probe, plasma or a conductive conforming membrane, and to a probe on the underside of the wafer.

Abstract: An embodiment of a sensing element (10) for a gas vapor detector (24) is formed from a gold-palladium alloy. The sensing element (10) is highly sensitive to phosphine or arsine gas. The by volume palladium concentration of the sensing element is typically less than 20%. The sensing element (10) is used as an active element in a gas vapor detector (24).

Abstract: A current in a circuit is measured without breaking the circuit. A relatively low resistance element in the circuit such as a component lead is chosen. A current is forced through the element and the voltage drop measured. Another current is forced through the element and the voltage drop measured. The values of these currents and voltages are used to determine the original current in the circuit.

Abstract: A system 20 for measuring the sheet resistance of a conductive layer on the top surface of a semiconductor wafer 22 is disclosed herein. In one embodiment, the system includes a chuck 30 electrically coupled to the backside surface of the wafer 22. The chuck 30 is capable of supporting the wafer 22 electrostatically. A signal source 40 provides an excitation signal to the wafer 22 and circuitry for monitoring an induced signal is provided. The sheet resistance on the top surface of the wafer 22 is determined from the measurements of the excitation and induced electrical signals. Other systems and methods are also disclosed.

Abstract: An instrument and method for measuring chemical properties, the instrument having electrodes suitable for immersion in a chemical solution. A voltage source and a current-sensing circuit are connected to the electrodes to measure the current produced in the solution in response to a voltage applied to the electrodes to determine a value of the chemical in the solution. The instrument and method further include background compensation for offsetting the value of the analyte by an amount which is reflective of the background value of the solution. The background value is stored in an internal memory of the instrument so that when new experimental measurements are taken, the measurements are immediately offset by the background portion of the new experimental measurements. This allows operation of the instrument at high gain levels, resulting in a broad dynamic range and greater useful precision in the output signal.

Abstract: A method for measuring the resistance or conductivity between two or more conductors which are placed against a semiconductor element, wherein in order to bring the contact resistance between the conductors and the element to, to hold it at,a predetermined value during measuring, the conductors are held at a constant distance and/or under constant pressure relative to the semiconductor element.

Abstract: Contamination of a fluid medium is measured using a thin-wafer sensor having a front surface and a back surface. The thin-wafer sensor is made of relatively pure p-type silicon and has a thickness less than the bulk diffusion length of the material. The back surface is placed in physical contact with the fluid being monitored either by building the sensor into a fluid testing chamber in line with the system using the fluid, or by immersing an encapsulated version of the sensor into the fluid medium. A photovoltaic generating and sensing system generates and measures e.g., the surface photovoltage (SPV), at the front surface. A series of SPVs are measured and used to derive the minority carrier diffusion length L of the sensor. The carrier diffusion length value is used to calculate the surface recombination velocity at the back surface.

Abstract: An improved method for measuring contact resistance during device testing is disclosed. After a device under text has been properly positioned to make a contact with a test fixture, a first test current is forced between two pins of the device under test through an isolating diode and the voltage drop associated therewith is measured. Then, a second test current is forced to take the same path and the voltage drop associated therewith is also measured. The values of the forced currents and the measured voltage drops are then used to determine the dynamic resistance of the path, which includes the resistance of two contacts. The determined dynamic resistance or a derivative thereof is then used as an indication of the contact resistance between the test fixture and the device under test.

Abstract: A method and apparatus for monitoring and locating the presence of fluids beyond a containment vessel. A multiplicity of plates having conductive affinity are strategically oriented adjacent the area of liquid storage and periodic surveillance relying on conductivity of the substrate within which the electrodes have been placed are made such that disturbances in the conductivity correlates with migration of fluid being contained. The method and apparatus may be utilized to detect migration of salinated fluids into a region where previously less salination existed.

Abstract: A method is provided for measuring subsurface soil or rock temperatures remotely using electrical resistivity tomography (ERT). Electrical resistivity measurements are made using electrodes implanted in boreholes driven into the soil and/or at the ground surface. The measurements are repeated as some process changes the temperatures of the soil mass/rock mass. Tomographs of electrical resistivity are calculated based on the measurements using Poisson's equation. Changes in the soil/rock resistivity can be related to changes in soil/rock temperatures when: (1) the electrical conductivity of the fluid trapped in the soil's pore space is low, (2) the soil/rock has a high cation exchange capacity and (3) the temperature changes are sufficiently high. When these three conditions exist the resistivity changes observed in the ERT tomographs can be directly attributed to changes in soil/rock temperatures. This method provides a way of mapping temperature changes in subsurface soils remotely.

Abstract: An apparatus for monitoring and testing a twisted pair, particularly useful for an Ethernet network. First and second DC currents alternated with one another are applied to both ends of the line, asynchronously. By monitoring the potential on the line, a determination is made as to the condition of the line. For example, shorted, crossed, improperly terminated or open conditions can be detected. A visual indication of the condition of the line is provided and additionally, the visual indication provides an indication of the traffic level in the network.

Abstract: A measuring circuit with a biosensor utilizing ion sensitive field effect transistors having a simplified structure and is advantageous to integration. The measuring circuit comprises two ion sensitive FET input devices composed of an enzyme FET having an enzyme sensitive membrane on the gate and a reference FET, and a differential amplifier for amplifying the outputs of the enzyme FET and the reference FET. The drift phenomena of the ISFETs due to the use of a non-stable quasi-reference electrode as well as the temperature dependence thereof can be eliminated by the differential amplifier consisting of MOSFETs having the same channel as the ISFETs. The ISFET biosensor and the measuring circuit can be integrated into one chip.

Abstract: A printed circuit board having through-holes and a test land for testing the through-holes. The test land is composed of a pair of current measurement lands and a pair of resistance measurement lands in order to test accurately the packing conditions of the conductive paste packed in the through-holes, thereby improving the uniformity and completeness of conductive-paste packing in printed circuit boards.

Abstract: A device for detecting contaminants on a surface of a conductive test sample includes first and second probes for engaging contaminants on a test sample surface. The first and second probes are connectable to a device for measuring voltage drop and are dimensioned and configured for measuring voltage drop across contaminants on the test sample surface at a predetermined contact force. The predetermined contact force is selected to prevent the first and second probes from piercing the contaminants. The device also includes a device for biasing the probes against the contaminants on the test sample surface with the predetermined contact force. The device for biasing the probes against the contaminants on the test sample surface include a moveable probe arm and a counterweight on the moveable probe arm which permits the predetermined contact force between the first and second probes to be selected. The moveable probe arm is adapted for both horizontal and vertical movement.

Abstract: The resistivity of the surface of a semiconductor wafer is measured at different temperatures to determine the resistivity as a function of temperature. The temperature of the semiconductor wafer is varied by a heater in thermal contact with the semiconductor wafer, and the temperature is measured by a temperature sensor in thermal contact with the semiconductor. The heater is controlled by a control unit which adjusts the amount of heat provided by the heater, thereby controlling the temperature at which a measurement from a four-point resistivity probe is taken.

Abstract: In a non-destructive method for the detection of surface cracks in metals, an eddy current is induced in the surface region of a workpiece under test, at a frequency sufficiently high to generate an alternating magnetic field solely in the skin region of the workpiece. That alternating surface magnetic field is interrogated by means of a relatively small electro-magnetic induction sensor, having regard to the overall area of the induced magnetic field. The sensor provides a voltage output which is analysed, preferably in real time, to yield an indication sensor. Also described is a probe for performing such a method.

Abstract: A circuit and a method for measuring a quantity influencing the capacitance-voltage characteristic of a capacitive element, the measuring accuracy and the signal-to-noise-ratio being improved by determining such quantity on the basis of the area under the curve of the capacitance-voltage characteristic.

Abstract: A method and a device which uses a semiconductor type of sensor for detecting and measuring gas of the type such as hydrogen sulfide which depletes the oxygen component from the semiconductor sensor when exposed to the gas and thus lowers electrical resistance through the sensor which uses a pair of semiconductor gas detecting sensors. In one embodiment, the gas sensors are alternatively fed with gas to be sampled and air. In another embodiment, the gas sensors are alternatively turned on and off at predetermined intervals to replenish the depleted oxygen when the sensor is turned off and to sample when the sensor is turned on.

Abstract: A method of extracting an impurity profile from a diced semiconductor chip having cellular construction. The cells are arranged in a matrix the columns and rows of which have a defined column pitch a.sub.x and a defined row spacing a.sub.y. In accordance with the method, the diced chip is bevelled from its original surface to expose the cells. The two probes of a Spreading Resistance Profile (SRP) device are then placed in contact with the dopant regions of two cells in the same row of the matrix, the distance .DELTA.X between the probes being ma.sub.x, where m is an integer, and the total resistance R.sub.T between the probes is measured. The SRP device is then stepped through a plurality of rows in the matrix, contacting cells in the same two columns as in the case of the first measurement, thereby interactively generating a plurality of total resistance R.sub.T measurements. The total resistance R.sub.T measurements are then combined to obtain the doping profile of the dopant region.

Abstract: A method for modeling a conducting material sample or structure system, as an electrical network of resistances in which each resistance of the network is representative of a specific physical region of the system. The method encompasses measuring a resistance between two external leads and using this measurement in a series of equations describing the network to solve for the network resistances for a specified region and temperature. A calibration system is then developed using the calculated resistances at specified temperatures. This allows for the translation of the calculated resistances to a region temperature. The method can also be used to detect and quantify structural defects in the system.

Abstract: A method and apparatus for carrying out the checking of the state of wear of a covering fabric in a driving belt (2) mounted on a plurality of pulleys (3, 4, 5) by measuring the electric resistance variations of the belt fabric. The apparatus provides that at least two of the pulleys (3, 4, 5) should be electrically insulated with respect to each other and connected to an electric circuit (20) designed to apply an electric voltage to said pulleys in order to carry out the measuring of the electric resistance of the fabric exhibited by belt stretches (A, B) comprised between the pulleys themselves. The electric resistance thus found lends itself to be compared with predetermined resistance values corresponding to different states of wear of the belt (2) fabric. The work surface of the belt (2) is coated with an electrically conductive fabric (12) acting by contact on the pulleys (3, 4, 5) and having characteristics of tensile strength.

Abstract: A method of alternating current potential drop measurement is provided in which the flow of the current in the specimen is laterally confined by passing the applied current externally over and in the immediate proximity to the surface of the specimen. To this end, a voltage probe is provided having a longitudinally extending isolated conductor which is connected to one current contact of a pair of current contacts. In use, this is arranged to provide an external flow path for current applied to the specimen. The isolated conductor is arranged to lie adjacent to the voltage probe contacts. For convenience of mounting, the conductor may be implemented as a conductive track on a printed circuit board. The track may also be bifurcated in order to accommodate one or more short lengths of conductor which can be used to form one or more compensating inductive loops which latter may be wired to afford cancellation of picked-up induced emf.

Abstract: A method for inspecting a printed circuit board having through-holes filled with conductive paste and having a pair of current measurement lands and a pair of resistance measurement lands. The pairs of current measurement lands and resistance measurement lands are used to measure voltage and current through the through-holes using the four-probe method, thereby preventing incomplete inspection of printed circuit boards and improving the dependability of tests on the packing conditions of the conductive paste in the through-holes.

Abstract: A method and apparatus for determining the extent of contact between an electrically conducting tube and an electrically conductive tubesheet surrounding the tube, based upon the electrical resistance of the tube and tubesheet. A constant current source is applied to the interior of the electrically conducting tube by probes and a voltmeter is connected between other probes to measure the voltage at the point of current injection, which is inversely proportional to the amount of contact between the tube and tubesheet. Namely, the higher the voltage measured by the voltmeter, the less contact between the tube and tubesheet.

Abstract: An electrode for use in the electrical investigation of a medium such as a borehole wall, comprises a sheet (32) of electrically resistive material having opposed first (34) and second (33) surfaces, one or more elongate electrical conductors (35,36) of low resistivity, an end face of each conductor abutting the first surface of the sheet (32) and means for sensing electric current passing through each conductor. In use, the second surface (33) of the sheet (32) is exposed to the medium to be investigated.

Abstract: The method of determining interactions due to direct currents on adjacent buried metal structures at least one of which is connected to a direct current generator such as a cathodic protection device, consists in placing calibrated specimen test metal pieces in the vicinity of the buried metal structures, the test pieces being made of materials that are analogous to those of the structures. The test pieces are spaced apart from each other by a distance L' equal to the distance L between the structures. Reference electrodes are placed in the immediate proximity of the specimen metal test pieces and simultaneous measurements are performed firstly of the potentials of the specimen test pieces relative to the reference electrodes, and secondly of the currents flowing through the calibrated specimen test pieces when they are electrically connected to respective ones of the structures.

Abstract: A method and apparatus for testing the resistance of armature commutator connections and the resistance values of individual windings uses a pair of independent constant current sources connected across opposite pairs of armature windings through their respective commutator bars. The constant current sources are identical in output current and are connected in opposite polarity to minimize circulating current flowing in other windings of the armature. The voltages developed across windings adjacent the two current sources are combined and are a function of the resistances of the connections between the windings and the commutator bars. The voltages across each constant current source represent the resistance of the winding to which it is connected.

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: The invention relates to a method and means for measuring the depth of cracks, using a potential probe connected to a measuring instrument and having two current terminals and additional voltage-measuring terminals (potential probe method).The object of the invention is to eliminate the separate calibration devices needed for the checks and collective measurements necessary when using known potential probes, and to make the check measurements in conjunction with the actual depth-measuring process.This problem is solvable by using a potential probe (S) as per the drawing, where at least two pairs of terminals (1+2, 3+4) having known but different spacings serve as adjustment measuring portions and are connected to an adjustment circuit (JM, UM) in a measuring-instrument microcomputer (M) and an additional pair of terminals (2, 3) having a known spacing serve as a crack-depth measuring portion and are connected to a crack-depth measuring circuit (TM) in the microcomputer.

Abstract: A probe holder mounts a pair of spaced current probes, a pair of spaced primary voltage probes inward of such current probes and a pair of spaced secondary voltage probes outward of such current probes. Each of the secondary voltage probes and the nearer thereto of the primary voltage probes is on the same equipotential contour calculated by assuming that the current probes contact and pass current through a planar homogeneously resistive sheet with infinite boundaries and of infinitesimal thickness. Electroconductive bodies are evaluated for resistive anomalies therein by contacting the body of all the probes and passing current through the body between the current probes. The voltages V.sub.a, V.sub.b and V'.sub.a, V'.sub.b responsively sensed on the surface of such body by, respectively, such two primary probes and such two secondary probes are used to derive first and second signals as functions of the voltage differentials V.sub.a -V.sub.b and V'.sub.a -V'.sub.b respectively.

Abstract: A process for obtaining a multifunctional, ion-selective-membrane sensor is disclosed, which process comprises the following steps:a) preparation of a siloxanic prepolymer, followed by one or more deposition(s) of said siloxanic prepolymer on a device of MOS or ISFET type;b) preparation of a solution containing an ionophore, a monomer of a polymerisable olefin, 2,4-toluenediisocyanate and a dialcohol or a diamine or a glycol or a trialcohol or a triamine, which preparation is followed, after that said solution has been kept stirred for at least 48 hours at room temperature, by the deposition thereof on the siloxanic prepolymer, which deposition is carried out by means of a spinner;c) photochemical treatment in the presence of a photoinitiator by means of UV light, with a suitable mask being used, which allows the exposure to UV light to take place on one gate only;d) chemical washing of the sensor, by means of an organic solvent;e) thermal treatment ("thermal curing"), so as to complete the reactions of polym