Abstract: A probe suitable for probing a semiconductor wafer that includes an active circuit. The probe may include a flexible interconnection between the active circuit and a support structure. The probe may impose a relatively low capacitance on the device under test.

Abstract: The present invention relates to an electrical specific resistivity probing robot, and it is directed to automatically measuring a three-dimensional electrical specific resistivity structure of an underground shallow region by installing a plurality of probing electrodes at regular intervals along a robot-moving caterpillar to measure difference of potentials of the electrodes at a ground plane. The electrical specific resistivity probing robot of the present invention includes a frame (10); a driving means (20) installed under the frame; a pair of insulating caterpillars (30, 31) installed to both sides of a lower portion of the frame and driven by the driving means; a plurality of probing electrodes (40) installed along track (31) circumferences of the caterpillars at regular intervals; a slip ring (50) electrically slip-connected to the probing electrodes one by one; and a cable (60) electrically connected to the slip ring.

Abstract: Apparatus and methods for testing a light fixture power circuit are therefore provided. The light fixture power circuit may energize a fluorescent lamp by providing power at first and second power terminals. The lamp holder may include a lamp pin guide for guiding the tube's contact pins toward the first and second power terminals. The apparatus may have probes that simulate the tube's contact pins. The probes may be robotically inserted into the lamp holder in a manner that is similar to the manner in which the contact pins would be inserted. This may eliminate the requirement to use fluorescent tubes to test the light fixture power circuit. The apparatus may include circuitry for testing the impedance of the light fixture power circuit at the first and second power contacts.

Abstract: Systems and techniques for probing interfaces between electrodes and conductive solutions. In one aspect, devices can include a time variable source of power configured to output power that varies in time over a pair of output conductors, an electrode connected to a first of the conductors, an extrinsic inductive impedance connected between the pair of output conductors, and an impedance sensor connected to one or both of the output conductors and configured to measure net impedance between the pair of output conductors based on a known current or voltage output by the time variable power output. The measured net impedance includes the extrinsic inductive impedance and an impedance of the interface. The electrode is configured to be submersed in a conducting solution and form an interface with the conducting solution.

Abstract: The present invention provides a probe apparatus and method as described below for use as a non-destructive testing (NDT) device to detect and locate structural flaws in a composite laminate. In preferred embodiments, the method includes measuring effective thermal conductivity (Ke) of the laminate using one contact surface, non-invasively. The device is preferably portable and battery-operated. The thermal conductivity method on which the device is based is much simpler to use than the known devices for NDT and allows the utilization of a direct correlation between thermal conductivity and mechanical strength in the case of polymer composites. The device may also be used for process control in manufacturing and monitoring materials in service.

Abstract: Nanoscale impedance microscopy and related methods, circuit and/or apparatus capable of quantitatively measuring magnitude and phase of alternating current flow.

Abstract: Disclosed are a connector for measurement of electric resistance, by which necessary electrical connection is surely achieved even when a circuit board to be inspected is large in area and has a great number of small-sized electrodes to be inspected, and measurement is surely performed with high precision, and which can be produced at a low cost, and an electric resistance-measuring apparatus and an electric resistance-measuring method for circuit boards, which make use of this connector. The connector for measurement of electric resistance has a first electrode sheet, an anisotropically conductive elastomer sheet arranged on a back surface of the first electrode sheet and having through-holes formed corresponding to the electrodes to be inspected, and a second electrode sheet arranged on a back surface of the anisotropically conductive elastomer sheet.

Abstract: An electrical junction box is adapted to be set in a conductivity inspection device. The conductivity inspection device includes a sensing pin assembly and guide pins, the guide pins extending beyond the sensing pin assembly. The electrical junction box includes a casing including a containing section and at least two guide holes formed in a surface wall of the casing, the guide holes being spaced away from each other by a given distance. The casing is shaped such that when the electric junction box is set in the conductivity inspection device, the guide pins are inserted into the guide holes before the sensing pin assembly is inserted into the containing section.

Abstract: Strips, particularly test strips and adapters for test strips, for use in meters for the electrochemical measurement of analyte in a sample material and in particular the glucose concentration of a sample of blood. The strips comprise a plurality of working connectors, for interfacing with the meter, coupled to one or more working electrodes. The strips are of particular use in adapting multi-input meters for single input use.

Abstract: An object of the present invention is to provide a measuring apparatus such as a conduction characteristics evaluation apparatus, a probe microscope, etc. having a nanotube probe, wherein the measuring apparatus is succeeded in reducing the electrical resistance of the carbon nanotube as well as the electrical resistance between the carbon nanotube and a metal substrate to improve electrical conduction characteristics of the nanotube probe and attain a uniform diameter, thus improving the measurement accuracy. In order to solve the above-mentioned problem, there is provided a conduction characteristics evaluation apparatus having a nanotube probe made of a nanotube coated by tiny fragments of graphene sheets to improve the wettability with respect to metal materials and then coated by a metal layer, or a conduction characteristics evaluation apparatus having a nanotube probe made of a metal-coated amorphous nanotube composed of tiny fragments of graphene sheets.

Abstract: A scanning probe microscope system comprising a hollow probe 3, a tube 4 connected to a rear end 32 of the hollow probe 3, a support table 1 provided under the hollow probe 3, and a substrate 2 and a means 5 for washing the hollow probe 3 that are fixed to the support table 1, a sample S passing through the tube 4 and the hollow probe 3, and the substrate 2 and the washing means 5 being moved by the support table 1 such that each of them opposes the hollow probe 3.

Abstract: A determination of an equivalent series resistance (ESR) effect for high frequency filtering performance of a filtered feed-through assembly is described. A low frequency signal is introduced to a filtered feed-through assembly. ESR limit of the filtered feed-through is determined based on the low frequency signal.

Abstract: Disclosed are a connector for measurement of electric resistance, by which necessary electrical connection is surely achieved even when a circuit board to be inspected is large in area and has a great number of small-sized electrodes to be inspected, and measurement is surely performed with high precision, and which can be produced at a low cost, and an electric resistance-measuring apparatus and an electric resistance-measuring method for circuit boards, which make use of this connector. The connector for measurement of electric resistance has a first electrode sheet, an anisotropically conductive elastomer sheet arranged on a back surface of the first electrode sheet and having through-holes formed corresponding to the electrodes to be inspected, and a second electrode sheet arranged on a back surface of the anisotropically conductive elastomer sheet.

Abstract: The characteristics of an object are measured using an electrical characteristics measurement device in which a probe includes a signal terminal, a ground terminal, and a variable resistance element is connected via a coaxial cable to a measuring instrument. The calibration of the probe entails adjusting the resistance value of the variable resistance element, setting the impedance of the distal end vicinity of the probe essentially to zero, and establishing a match with the coaxial cable and measuring instrument. When the electrical characteristics of the object are measured, the resistance value of the variable resistance element is varied in accordance with the impedance created by the side of the circuit containing the measurement object as viewed from the contact between the object and the signal terminal and ground terminal, and the input impedance of the probe is set to a value that does not affect the operation of the object.

Abstract: A method is described for controlling the soot deposition on sensors. A sensor element is provided, which includes a first electrode and a second electrode. Different measuring voltages U1 and U2 can be applied to the sensor element. During a first time period t1, the sensor element is operated at a higher voltage U1 until a triggering threshold AP of the sensor element is exceeded, while it is operated at a voltage U2, which is different from higher voltage U1, U2 being lower than voltage U1, during a second time period t2.

Abstract: The present invention relates to a method of fabricating a vertical probe head, whereas the vertical probe head is formed by the combination of at least a probe, a bottom guide plate and a top guide plate having at least a hole matching the probe. The probe is fabricated by a LIGA-like process combining with the processes of photolithography, etching and electroforming, and so on, so that the probe is equipped with comparatively better precision, strength and reliability and yet can be custom-made for satisfying various demands. In addition, both the top and bottom guide plates are made by a means of non-mechanical machining, which respectively is fabricated by processing a substrate using means of photolithography, etching and mask so as to fabricate holes for matching with the aforesaid probe.

Abstract: The present invention relates to a quick reference electrical voltage testing tool utilizing a variable voltage range light bulb and digital read out voltage meter both incorporated in the testing tool's handle. The variable voltage range light bulb indicates to the user the knowledge of voltage present and the digital voltage read out indicates the measured amount of voltage available to the tested component. This allows for a faster diagnosis of an electrical problem particularly when voltage sensitive components are being tested. When testing electrical components for non-operation, this quick reference tool will allow a much quicker diagnoses of an electrical problem without the need of a voltage meter.

Abstract: A contacting-type conductivity sensor includes a plurality of electrodes disposed on a distal surface of a substrate. The substrate includes a plurality of vias through which electrical interconnection to the electrodes is accomplished. The conductivity sensor can employ two or four electrodes and may have a temperature sensitive element disposed on the distal surface. The electrodes may be patterned or otherwise deposited using semiconductor processing techniques.

Abstract: A semiconductor integrated circuit device includes an internal circuit. A plurality of power supply nodes are connected with the internal circuit, and a plurality of pads are respectively connected with the plurality of power supply nodes. A switch section is configured to connect the plurality of power supply nodes one after another in a probe test mode and to separate the plurality of power supply nodes from each other in a product use mode. A power supply voltage is applied to one of the plurality of pads in the probe test mode, and the power supply voltage is applied to each of the plurality of pads in the product use mode. The switch section may include n switches (n is a natural number) provided for the plurality of power supply nodes.

Abstract: An apparatus for measuring spin polarization via Point Contact Andreev Reflection (PCAR) at a magnet-superconductor junction, with variable magnetic fields and temperature control. A cryostat probe investigates superconducting energy gap and Andreev reflection in superconductor-half metal junctions, in a wide range of magnetic fields and temperature from 2K-300K. The cryostat probe is integrated with a commercial physical properties measurement system. The measurement probe includes a rotary-translation stage with coarse and fine screws that enable a user to make point contacts in a cryogenic, evacuated environment where the point contact junction can be controlled at room temperature by turning a knob. Copper wires are connected as electrical leads from an aluminum housing, descend down to a copper housing, for measurement, when contact is made by tip with a half-metal sample, such as CrO2.

Abstract: A method and apparatus for determining a voltage, such as a bias voltage, supplied by an integrated circuit. A nominal terminating resistor is connected across a first and a second input/output pads from which the voltage is supplied. The voltage is measured across third and fourth pads connected, respectively, to the first and second pads. In an alternative embodiment the functionality of the third and the fourth pads is multiplexed between chip operational circuitry unrelated to the voltage to be measured and a connection to the first and second pads for measuring the voltage.

Abstract: Apparatus and methods for measuring the electrical resistance of conductive materials are disclosed. In one embodiment, an apparatus includes a housing, and first, second, third, and fourth conductive members projecting outwardly from the housing. The conductive members are engageable with an electrically-conductive material at a plurality of points distributed along a measurement axis. In an alternate embodiment, at least some of the conductive members include a spring-loaded portion such that a contact portion of the conductive member projects outwardly from the housing by a variable distance. In operation, the electrical resistance of the electrically-conductive material is determinable from a known current applied between the first and fourth conductive members, and a voltage measured between the second and third conductive members.

Abstract: A method of making an interposer having an array of contact structures for making temporary electrical contact with the leads of a chip package. The contact structures may make contact with the leads substantially as close as desired to the body of the chip package. Moreover, the contact structures can be adapted for making contact with leads having a very fine pitch. In a first embodiment, the contact structures include raised members formed over a body of the interposer. A conductive layer is formed over each of the raised members to provide a contact surface for engaging the leads of the chip package. In another embodiment, the raised members are replaced with depressions formed into the interposer. A conductive layer is formed on an inside surface of each depression to provide a contact surface for engaging the leads of the chip package. Moreover, any combination of raised members and depressions may be used.

Abstract: The preferred embodiments are directed to a method and apparatus of operating a scanning probe microscope (SPM) including oscillating a probe of the SPM at a torsional resonance of the probe, and generally simultaneously measuring an electrical property, e.g., a current, capacitance, impedance, etc., between a probe of the SPM and a sample at a separation controlled by the torsional resonance mode. Preferably, the measuring step is performed while using torsional resonance feedback to maintain a set-point of SPM operation.

Abstract: An oil condition sensor is proposed which can accurately determine the degree to which oil is contaminated with metallic powder. It includes a permanent magnet and a sensor head provided around the permanent magnet. The sensor head includes a cup-shaped electrode and a plurality of rod-shaped conductors that are axially spaced from the cup-shaped electrode. The conductors are connected to a power supply through separate resistors. When the amount of metallic powder in the oil increases, a greater number of conductors are electrically connected to the cup-shaped electrode. Thus, by finding the number of conductors electrically connected to the cup-shaped electrode, it is possible to determine the degree to which the oil is contaminated with metallic powder. Since the resistors need not be immersed in the oil, their specific resistivities will scarcely change, so that the degree of contamination of the oil can be determined with high accuracy.

Abstract: A probe assembly for use with a battery impedance meter which minimizes excitation pick-up voltages by routing the wires from the meter to the battery cell terminals without forming a loop within a changing magnetic field caused by current drawn from the battery cell.

Abstract: An osmolarity measuring system is configured to receive a contact lens in a measurement chamber. The measurement chamber includes a volume of fluid, and a series of electrodes are configured to measure the electrical properties of the fluid. A processing device correlates the measured electrical properties with an osmolarity measurement. Further, the processing device is configured to track trends in stored osmolarity measurements and alert the user to take an action, including the cessation or alteration of product use.

Abstract: A probe for surface-resistivity measurement is provided in a surface-resistivity measuring apparatus for measuring a surface resistivity of a target. The probe includes an electrode and a contact portion. The contact portion has a specific resistance larger than the electrode. The contact portion is disposed on the electrode. The contact portion is capable of surface-contact with the target.

Abstract: An apparatus for detecting an intrusion of an environmental substance into an environmentally sealed electronic components package. The electronic components package generally includes a plastic coated or plastic enclosed electronic component, that includes a printed circuit board and/or integrated circuits. The intrusion of the environmental substance into the electronic components package can be measured by one of a plurality of monitors. The monitors can detect the presence of the environmental substance and alert a user that a break in the seal of the electronic components package has occurred.

Abstract: An oil condition sensor includes rod-shaped electrodes and an opposed cup-shaped electrode. The rod-shaped electrodes are connected to a first power supply through first fixed resistors having a predetermined threshold. The voltage from the first power supply is applied through the respective rod-shaped electrodes to first inputs of respective operational amplifiers. The sensor further includes a second power supply which produces a voltage applied to second inputs of the respective operational amplifiers. Each operational amplifier produces a predetermined voltage if the voltage applied to the first input falls below the voltage applied to the second input. The output of each operational amplifier is connected to the second input through a second fixed resistor.

Abstract: Apparatus and methods of measuring the electrical resistance of electrically-conductive materials are disclosed. In one aspect, an apparatus includes a substrate, and first, second, third, and fourth elongated conductive members. Each conductive member includes a first portion at least partially disposed on the substrate and a second portion. Each of the first portions is spaced apart from one or more adjacent first portions and is engageable with the electrically-conductive material along a contact length. The apparatus may include a source operatively coupled to the second portions of the first and fourth conductive members, and a meter operatively coupled to the second portions of second and third conductive members.

Abstract: A nanoprobe includes a substrate having a layer, which forms a projected portion. A plurality of conductive lines is adhered to the projected portion and the lines extend beyond an end of the projected portion by a distance to form contact points, wherein the lines are connected to material of the projected portion to provide stiffness and the contact points provide flexibility during use.

Abstract: Carbon nanotubes are formed on projections on a substrate. A metal, such as nickel is deposited on the substrate with optional platforms, and heated to form the projections. Carbon nanotubes are formed from the projections by heating in an ethylene, methane or CO atmosphere. A heat sensor is also formed proximate the carbon nanotubes. When exposed to IR radiation, the heat sensor detects changes in temperature representative of the IR radiation. In a gas sensor, a thermally isolated area, such as a pixel is formed on a substrate with an integrated heater. A pair of conductors each have a portion adjacent a portion of the other conductor with projections formed on the adjacent portions of the conductors. Multiple carbon nanotubes are formed between the conductors from one projection to another. IV characteristics of the nanotubes are measured between the conductors in the presence of a gas to be detected.

Abstract: A voltage probe includes a signal lead that is configured to be soldered to a probing location in a device that is to be probed by the voltage probe, and a first cable that is coupled to the signal lead and that is configured to conduct an output signal that is responsive to an input signal that is received by the signal lead from the device. The signal lead has a thermal conductivity of less than 200 Watts per meter Kelvin (W/mK). Methods and other systems for providing electrical connections to devices under test are disclosed.

Abstract: A voltage probe includes a first signal lead configured to receive a first signal from a device under test, a first probe-tip network that is coupled to the first signal lead and that has a frequency response that includes a first transmission zero, a first compensation network that is coupled to the first probe-tip network and that has a frequency response that includes a first transmission pole, a second signal lead configured to receive a second signal from the device under test, a second probe-tip network that is coupled to the second signal lead and that has a frequency response that includes a second transmission zero, a second compensation network that is coupled to the second probe-tip network and that has a frequency response that includes a second transmission pole, and a differential amplifier circuit that is coupled to the first compensation network and to the second compensation network, and that is configured to provide a third signal that is responsive to the first signal and to the second sign

Abstract: With a wafer having an indefinite shape or a broken wafer, it is hard for an operator to assign the design address of an edge chip and set a probe area. In a probe-area setting method of this invention, a wafer W is placed on a main chuck (18) that is movable at least in the X- and Y-directions. The main chuck (18) is moved, thus moving wafer W in the X- and Y-directions. All edge chips formed on the wafer W are retrieved by means of an upper camera (21A), thereby setting a probe area. To retrieve the edge chips, an edge chip is selected as one with which the retrieval should be started. The edge chips are successively retrieved in the turning direction of the wafer, as the chip retrieval direction is changed to the X- or Y-direction.

Abstract: A sensing element (2) for sensing a fluid (50) composition and a method of using the sensing element (2) are provided. The sensing element (2) includes an electrode base (36) having a first electrode (4) and a second electrode (6) disposed on the electrode base (36); the first electrode (4) and a second electrode (6) being electrically isolated one another except through an external circuitry (64); the first electrode (4) and the second electrode (6) defining a gap (42) between one another such that electrical conduction through a fluid (50) within the gap (42) is proportional to the composition of the fluid.

Abstract: Provided is a fabrication method of a semiconductor integrated circuit device which comprises forming a pushing mechanism by forming, over the upper surface of a thin film probe, a reinforcing material having a linear expansion coefficient (thermal expansion coefficient) almost equal to that of a wafer to be tested; forming a groove in the reinforcing material above a contact terminal, placing an elastomer in the groove so that a predetermined amount exceeds the groove, and disposing a pusher and another elastomer to sandwich the pusher between the elastomers. The present invention makes it possible to improve the throughput of wafer-level electrical testing of a semiconductor integrated circuit.

Abstract: A conductivity sensor (16) and control circuit (18) for determining the conductivity of a fluid is provided. Conductivity sensor (16) is formed of a first annular electrode (24) spaced apart from a second annular electrode (26) having a tubular portion (28) therebetween. The first annular electrode (24) and the second annular electrode (26) are coupled to a control circuit (18). The control circuit (18) preferably includes a square wave generating circuit (40), a current-to-voltage converter circuit (42) coupled to one of the electrodes, a buffer circuit (44) coupled to the other one of the electrodes, a synchronous detector circuit (46). The synchronous detector circuit (46) is operated using the square wave from square wave generator circuit (40). By oscillating between a negative and positive gain, a constant direct current output corresponding to the conductivity of the fluid between the first annular electrode and second annular electrode is provided.

Abstract: An integrated circuit die test probe has a non-flat tip. In one embodiment, the tip has an elongated pyramid shape that provides a cutting action while probing solder covered conductive pads. The tip shape helps maintain a uniform tip to pad resistance during testing by penetrating the solder layer and avoiding solder residue build up. The test probes significantly reduce the need for cleaning the probe tips to remove residue.

Abstract: A substrate, preferably constructed of a ductile material and a tool having the desired shape of the resulting device for contacting contact pads on a test device is brought into contact with the substrate. The tool is preferably constructed of a material that is harder than the substrate so that a depression can be readily made therein. A dielectric (insulative) layer, that is preferably patterned, is supported by the substrate. A conductive material is located within the depressions and then preferably lapped to remove excess from the top surface of the dielectric layer and to provide a flat overall surface. A trace is patterned on the dielectric layer and the conductive material. A polyimide layer is then preferably patterned over the entire surface. The substrate is then removed by any suitable process.

Abstract: A device and method for determining the sheet resistance of samples, in particular wafers and other two-dimensional objects, comprising a means for measuring the conductivity of the sample according to the eddy current technique, wherein the sample is introducible into a gap for measurement, and comprising a means for measuring the position of the sample in the gap for measurement and a computing means for determining the sheet resistance on the basis of the measured conductivity and of the position of the sample in the gap for measurement.

Abstract: A test carrier and an interconnect for testing semiconductor components, such as bare dice and chip scale packages, are provided. The carrier includes a base on which the interconnect is mounted, and a force applying mechanism for biasing the component against the interconnect. The interconnect includes interconnect contacts configured to make temporary electrical connections with component contacts (e.g., bond pads, solder balls). The interconnect also includes support members configured to physically contact the component, to prevent flexure of the component due to pressure exerted by the force applying mechanism. The support members can be formed integrally with the interconnect using an etching process. In addition, the support members can include an elastomeric layer to provide cushioning and to accommodate Z-direction dimensional variations.

Abstract: A full wafer probe card is disclosed along with related methods and systems. The probe card includes test probes comprising cantilever elements configured and arranged with probe tips in a pattern corresponding to an array of bond pads of semiconductor dice residing on a device wafer. The probe card may be fabricated from, for example, a silicon substrate and the cantilever elements may be fabricated using known silicon micro-machining techniques including isotropic and anisotropic etching. Additionally, conductive feedthroughs or vias are formed through the probe card to electrically connect the probe tips with conductive pads on an opposing side of the substrate which interface with test contacts of external test circuitry. The conductive feedthroughs may be formed as coaxial structures, which help to minimize stray capacitance and inductance. The inventive probe card allows for improved wafer level burn-in and high frequency testing.

Abstract: A low capacitance probe contact has electrically conductive contacts having fingers with opposing interior flat surfaces forming a slit there between. The fingers extend in a first direction with a mounting member extending in the opposite direction having a flat surface that is parallel to the flat surfaces of the fingers. The first and second electrically conductive contacts are secured to respective first and second electrically conductive contact pads formed on a substrate with the flat surfaces of the mounting members being positioned on the contact pads. The substrate and the electrically conductive contacts are captured within a housing having first and second members. One member has a base and extending sidewalls forming a recess that receives the substrate and the electrically conductive contacts and the other member has a periphery coextensive with the first member to capture the substrate and the electrically conductive contacts therein.

Abstract: Molten metal inclusion sensor probes have a sensing passage through which the molten metal passes, while direct current passes through the passage between two electrodes. The passage of an inclusion through the passage changes the resistance in the path, resulting in a pulse indicating its size, and enabling the number of particles in a sample to be counted. Previously the passage has been cylindrical, with or without a conical entrance, or of randomly smoothed profile produced by melting the probe material. High levels of background noise make pulse detection difficult, and operation is improved by the passage decreasing smoothly in cross-section in the flow direction, preferably with a parabolic or elliptical profile, and preferably with the exit of the same profile. The wall surface is formed to a smoothness of better than 1.016 micrometers (40 microinches), preferably 0.254 micrometers (10 microinches), permitting pre-determination of the optimum testing and conditioning currents required.

Abstract: A method and apparatus for detecting the AC component of a signal. The present invention, which uses with a digital multimeter in a DC mode allows the DC component of a signal to be detected simultaneously with the measurement of the signal without affecting the measurement precision of the signal, is most advantageous for use in situations where the presence of the AC component, and not its precise magnitude, is what needs to be known.

Abstract: A projectile fuze detects transitions between target layers by an electronic antenna radiating laterally into the target material and coupled to a pullable oscillator whose frequency shifts as the target material changes while the projectile penetrates. A frequency shift threshold detector relates the observed frequency shifts to a stored target profile to detonate the projectile after the desired layer penetration.

Abstract: In a solids profile measurement system for determining the quality of a solids bed formed from a liquid-solid slurry in a vessel, a sensor adapted to generate signals indicative of a profile as measured by progressively immersing the sensor deeper into the slurry is provided. An extension mechanism, at least a portion of which is coupled at one end to the sensor and at an opposite end to a piece of processing equipment, is provided to affect retrograde movement in a first direction to immerse the sensor in a slurry, and in a second direction opposite the first direction. A controller in communication with the extension mechanism is also provided and issues commands thereto and receives signals generated by the sensor.

Abstract: The inventive apparatus is capable of accurate contactless sample conductance measurements. In accordance with the invention, a three coil apparatus for inductive conductance measurements comprises at least three coils, (or inductive devices,) a radio frequency (RF) generating device in conjunction with electronic circuitry for radio frequency amplitude measurement and comparison of radio frequency amplitude signals. The attainable accuracy is improved over that achieved using other conventional non-contact means by processing the differences of RF amplitude signals observed across pairs of sensing coils. Also, this invention does not require more complex RF signal processing, such as analysis of in-phase and quadrature voltage data. In a preferred embodiment, the natural resonance frequencies of the two sensing coils are tuned slightly off the RF driving frequency such that a monotonic response across a wide range of the sample's conductivity is achieved.