Abstract: A capacitive sensor includes a tubular outer conductor, a tubular inner conductor coaxial with the outer conductor, and an electrically insulated chamber between the inner and outer conductors. The material sample to be measured is introduced into the chamber. The sensor is shielded against electric fields to maximize measurement accuracy. The shielding completely encloses the chamber during operation and may include a removable cap, a valve, or a screen made of a conductive material. A measurement circuit connected to the sensor includes a reference oscillator that oscillates at a constant frequency and a test oscillator that oscillates at a frequency determined by the sensor capacitance. A circuit displays a value representing the sensor capacitance in response to the frequency difference between the test oscillator frequency and the reference oscillator frequency.

Abstract: A film position detection apparatus and a method for precisely detecting a film position are provided. An image film projection apparatus is also provided for correcting deflections of images through precisely detecting a film position and thereby projecting images recorded on the film in a good condition. A film position detection means has a ground electrode attached to a movable picture gate; detection electrodes placed in a fixed picture gate; and auxiliary electrodes placed around the detection electrodes. The auxiliary electrodes suppress erroneous variations in electrostatic capacitance generated between the ground electrode and the detection electrodes. As a result, accuracy in film position detection by the detection electrodes is improved for achieving precise detection.

Abstract: An ice detection sensor for placement on a surface of a body subject to ig includes a Pyrex glass or silicon block for disposal on the body surface, the block having a cavity therein, a diaphragm bonded to the silicon block and covering the cavity, a drive electrode disposed in the cavity and operable to deflect the diaphragm upon application of voltage between the drive electrode and the diaphragm, and a second electrode operable to detect motion of the diaphragm. The diaphragm is movable by the drive electrode when there is water covering the diaphragm and when the diaphragm is not covered and the diaphragm is not movable by the drive electrode when there is ice covering the diaphragm. The second electrode is adapted to detect movement and non-movement of the diaphragm, whereby to detect whether ice covers the diaphragm.

Abstract: An apparatus and method for measuring the dielectric constant or permittivity at a plurality of positions on a test specimen are provided. Accordingly, the present invention enables the spatial variance of the dielectric constant, i.e., the dielectric homogeneity, of the test specimen to be measured. In particular, high resolution dielectric homogeneity measurements are performed at low frequency (100 kHz to 10 MHz) using a specially designed guarded electrode assembly and a specially selected high permittivity matching liquid. The guarded electrode assembly comprises a guarded electrode surrounded by a guard electrode which is supported over a test specimen resting on a planar electrode. The test specimen and the planar electrode are immersed in a dielectric fluid. The guarded electrode as well as the guard electrode, which extends into the dielectric fluid, are translated across the test specimen while the capacitance between the guarded electrode and the planar electrode is measured.

Abstract: The present invention is an improved ice sensor which is particularly effective in measuring and quantifying non-uniform, heterogeneous ice typically found on aircraft leading edges and top wing surfaces. In one embodiment, the ice sensor comprises a plurality of surface mounted capacitive sensors, each having a different electrode spacing. These sensors measure ice thickness by measuring the changes in capacitance of the flush electrode elements due to the presence of ice or water. Electronic guarding techniques are employed to minimize baseline and parasitic capacitances so as to decrease the noise level and thus increase the signal to noise ratio. Importantly, the use of guard electrodes for selective capacitive sensors also enables distributed capacitive measurements to be made over large or complex areas, independent of temperature or location, due to the capability of manipulating the electric field lines associated with the capacitive sensors.

Abstract: The invention is a tester that uses a capacitive probe to test whether components that have multiple power and/or ground pins are correctly oriented relative to the signal-pin tracks on a circuit board. The tester connects, to the signal-pin track to which the pin under test is connected, a test-signal source that supplies to that pin a relatively high-voltage test signal. The tester actively guards the pin by applying to the remaining component pins, through the tester scanning system and its internal resistance, a signal that has the same voltage as that sensed by the capacitive probe. If the component is oriented such that one of the multiple power or ground pins is connected to the signal-pin track to which the test signal is applied, the test signal appears also at the other power or ground pins, since these pins are interconnected by a low impedance path through the component.

Abstract: A roof-mounted passenger position sensor array of capacitive coupling passenger position sensors, to determine position and motion of a passenger by analysis of distances of the passenger to the various sensors of the array and analysis of the changes of said distances with time.

Abstract: A capacitance sensor assembly for use with a label detection and registration system for detecting a lateral edge of a label on a web bearing a plurality of such labels and moving in a longitudinal direction through a capacitance gap in the sensor assembly. The capacitance sensor assembly includes a reference plate electrode, and a pair of sensor electrodes extending substantially parallel to and spaced apart from the reference plate electrode to form the capacitance gap. The pair of sensor electrodes has a differential capacitance, when the web bearing the plurality of labels thereon is in the capacitance gap, which is used to provide a signal indicative of the lateral edge of the label.

Abstract: The present invention relates to a device for the contactless detection of the position of a moving webs. The web has on one side of the web a detector electrode covering its entire width and on the other side in the area of the web edges transmission electrodes fed by an oscillator in phase opposition, so that the capacitive couplings between the transmission electrodes and the detector electrode respond in opposing fashion to deviations of the web from the central position. The signal received by the detector electrode is processed by a current to voltage converter with a very small input impedance so that the potential of the detector electrode remains at zero, and virtually no capacitive displacement currents flow to a screening electrode In this way, the sensitivity of the measurement array is independent of the web width.

Abstract: A capacitive proximity or limit switch comprises a capacitive probe having a sensor electrode and a guard electrode. The sensor electrode is connected to an oscillator formed by a feedback system of two operational amplifiers, of which one operational amplifier is configured as a differential amplifier, the other operational amplifier as a voltage follower. The probe electrode is connected to the inverting input of the differential amplifier, in the feedback circuit of which a capacitor is provided, as a result of which the AC gain is determined. An adjustable portion of the output voltage of the differential amplifier is applied to the non-inverting input of the voltage follower, the output of which is connected to the non-inverting input of the differential amplifier to which the guard electrode is connected.

Abstract: A capacitive type proximity sensor having improved range and sensitivity between a surface of arbitrary shape and an intruding object in the vicinity of the surface having one or more outer conductors on the surface which serve as capacitive sensing elements shaped to conform to the underlying surface of a machine. Each sensing element is backed by a reflector driven at the same voltage and in phase with the corresponding capacitive sensing element. Each reflector, in turn, serves to reflect the electric field lines of the capacitive sensing element away from the surface of the machine on which the sensor is mounted so as to enhance the component constituted by the capacitance between the sensing element and an intruding object as a fraction of the total capacitance between the sensing element and ground.

Abstract: According to the preferred embodiment, an erosion and dishing monitor is provided that facilitates the accurate optimization of a planarization process as in semiconductor process. The dishing monitor comprises at least two monitor structure sets embedded in a semiconductor substrate, the monitor structure sets comprising a plurality of monitor structures connected together with a plurality of connective conductors. The erosion monitor comprises a plurality of elongated conductors embedded into a semiconductor substrate, the plurality of conductors having varying conductor widths and adjacent substrate widths.

Abstract: A capacitive measuring device with a measuring electrode (3) arranged some distance from a counter-electrode (8), a dielectric material for analysis is arranged between the electrodes (3, 8), and a measuring current (IC) is supplied to the measuring electrode (3) and the capacitance-dependent capacitor voltage (UC) is measured and evaluated.

Abstract: A plate array for moisture sensors has a transmitter electrode and a detector electrode interposed between portions of a phase electrode. The transmitter and phase electrodes are driven with alternating current signals having a one hundred and eighty degree phase difference so as to induce a signal at the detector electrode relating to a moisture content of a material in the electrical fields which has a reduced sensitivity to electrically loading the material, such as from contact with a hand or steel roller.

Abstract: A capacitance sensor assembly for use with a label detection and registration system for detecting a lateral edge of a label on a web bearing a plurality of such labels and moving in a longitudinal direction through a capacitance gap in the sensor assembly. The capacitance sensor assembly includes a reference plate electrode, and a pair of sensor electrodes extending substantially parallel to and spaced apart from the reference plate electrode to form the capacitance gap. The pair of sensor electrodes has a differential capacitance, when the web bearing the plurality of labels thereon is in the capacitance gap, which is used to provide a signal indicative of the lateral edge of the label.

Abstract: A computer-based method and apparatus for fastener hole inspection including a capacitive probe with a plurality of sensor elements, means for grounding the faster hole, and an electronics unit electrically connected to the probe for sequencially charging one of the plurality of sensor elements while applying a guard potential to the remaining sensor elements and adjacent electrical components to eliminate residual capactitances. A profile of the fastener hole is generated by evaluating, through a series resistor, the discharge waveforms of the plurality of sensor elements by converting the capacitance measurements obtained to distance measurements. A centering algorithm is employed to compensate for malalignment of the capacitive probe in the fastener hole.

Abstract: An electrostatically actuated micromechanical sensor having a guard band electrode for reducing the effect of transients associated with a dielectric substrate of the sensor. A proof mass, responsive to an input, is suspended over the substrate and one or more electrodes are disposed on the substrate in electrostatic communication with the proof mass to sense the input acceleration and/or to torque the proof mass back to a null position. A guard band electrode is disposed over the dielectric substrate in overlapping relationship with the electrodes and maintains the surface of the substrate at a reference potential, thereby shielding the proof mass from transients and enhancing the accuracy of the sensor. A dissolved wafer process for fabricating the micromechanical sensor is described in which the proof mass is defined by a boron doping step. An alternative fabrication technique is also described in which the proof mass is defined by an epitaxial layer.

Abstract: A method for detecting extent of cross-linking of a high impedance polymer material during a pre-cure state, the method including: placing an insulated ground plane adjacent to the polymer material and substantially parallel to a sensor; applying a test signal through a sensor to the material and through a reference resistance; determining a voltage difference between the test signal applied to the material and the reference resistance as the reference voltage; and correlating the voltage difference as a relative indicator of the extent of cross-linking which has occurred within the polymer material. Also disclosed is a device for implementing the subject method.

Abstract: Apparatus for inspecting non-round annular containers includes elongated capacitive sensors, cooperating oscillators, which convert the sensor signal to a voltage corresponding thereto, and an electronic processor which receives the voltage and determines thickness. A displaceable electromechanical member is operatively associated with the sensor and emits an electrical signal corresponding to the degree of displacement of the sensor by a container being inspected. The electronic processor corrects the thickness determination by an adjustment of container diameter at the specific location where thickness is being monitored in order to compensate for container diameter variations due to the non-round characteristic of the container. In a preferred embodiment, linkage members secured to the rear of the sensor at a plurality of locations cooperate with a single displaceable element which converts the mechanical displacement of the sensor into a corresponding electrical signal.

Abstract: An electrostatically actuated micromechanical sensor having a guard band electrode for reducing the effect of transients associated with a dielectric substrate of the sensor. A proof mass, responsive to an input, is suspended over the substrate and one or more electrodes are disposed on the substrate in electrostatic communication with the proof mass to sense the input acceleration and/or to torque the proof mass back to a null position. A guard band electrode is disposed over the dielectric substrate in overlapping relationship with the electrodes and maintains the surface of the substrate at a reference potential, thereby shielding the proof mass from transients and enhancing the accuracy of the sensor.

Abstract: An electronic caliper configuration making such calipers more reliable in the presence of liquid and particulate contaminants. Included in the caliper configuration is an elongated cavity added to the main beam of the caliper. The cavity is sealed with a cover. The measuring scale element of the measuring transducer, and the associated shorter pickoff element are mounted in this cavity. The depth bar, ordinarily attached to the sliding jaw in conventional calipers, is inserted into the cavity through a hole or holes aligned parallel to the longitudinal axis of the caliper and internally joined to the moving transducer element. A conventional lip seal provides an effective seal around the diameter of the depth bar. An external portion of the depth bar is coupled to the sliding jaw of the caliper via axially rigid linkage or alternately an axially rigid flexure. In this way, the internally isolated transducer elements can be actuated by the external sliding caliper jaw.

Abstract: The present invention is an improved ice sensor which is particularly effective in measuring and quantifying non-uniform, heterogeneous ice typically found on aircraft leading edges and top wing surfaces.In one embodiment, the ice sensor comprises a plurality of surface mounted capacitive sensors, each having a different electrode spacing. These sensors measure ice thickness by measuring the changes in capacitance of the flush electrode elements due to the presence of ice or water. Electronic guarding techniques are employed to minimize baseline and parasitic capacitances so as to decrease the noise level and thus increase the signal to noise ratio. Importantly, the use of guard electrodes for selective capacitive sensors also enables distributed capacitive measurements to be made over large or complex areas, independent of temperature or location, due to the capability of manipulating the electric field lines associated with the capacitive sensors.

Abstract: A continuous liquid level measuring system having a guarded capacitance probe and related drive circuit for providing accurate level measurements, even when measuring the level of ionic and highly viscous fluids. The capacitance probe has two parallel electrodes, each constructed of a half-tube section, that are separated from each other by an insulated guard wire. The probe is excited by a 1 MHz excitation signal applied across the electrodes. The current through the electrodes is a function of the capacitance between the electrodes, which is affected by the relative permitivity of the surrounding liquid. The effects of highly viscous ionic liquids that adhere to the probe are reduced by exciting the guard wire with a guard signal that is 180.degree. out of phase from the probe's excitation signal. The guard signal changes the electric field existing in the space adjacent the junctions of the two electrodes to reduce any liquid coating effects on the level measurement.

Abstract: Guarded capacitance probe structures are constructed with guard electrodes surrounding one or more sensor electrodes and ground electrodes or grounded surfaces surrounding the guard electrodes. In a one sensor embodiment, the probe utilizes an apertured sensor electrode and the guard electrode both surrounds the sensor electrode and fills the aperture. This embodiment is particularly useful for measuring particle concentration in a fluid suspension contained within a vessel or pipe. The portion of the guard electrode within the aperture of the sensor electrode prevents electric field lines from emanating from the sensor electrode into the fluid suspension and toward infinity. A two sensor embodiment of the probe is useful for measuring flow velocities of fluid suspensions through cross correlation of the outputs generated by each sensor.

Abstract: The presence of an article at a specified location is detected by measuring a change in capacitance which is caused by the placement of the article at the specified location. The device used for this measurement includes an oscillator the frequency whereof is rendered highly sensitive to the capacitance being measured by structure which includes a triaxial cable and by electrical circuitry which includes a voltage follower circuit.

Abstract: An apparatus and method for processing materials by sensing roller, in which the sensing roller has a plurality of conductive rings (electrodes) separated by rings of dielectric material. Sensing capacitances or impedances between the electrodes provides information on thicknesses of the materials being processed, location of wires therein, and other like characteristics of the materials.

Abstract: A circuit tracer for determinating the location of a conductor, such as a wire, which is either an open or closed circuit, and which may lie underground. The tracer includes a transmitter which is connected to the conductor, a hand-held probe, and a receiver which is connected to the probe. The probe has three different sensors: an electric field sensor, primarily for locating the terminus of an open-ended conductor or for distinguishing such a wire in a bundled cable of wires; a differential electric field sensor, for determining the direction to and location of an open-ended conductor located above ground; and an inductive sensor for determining the direction to and location of a current-carrying conductor, including an open-ended conductor lying below ground. A switch selectively provides the output from one of the sensors to the receiver unit, which determines the magnitude of any signal based upon the direction the probe is pointing.

Abstract: Disclosed is a system that determines whether input and output leads of semiconductor components are present and properly soldered to a printed circuit board. The system includes a signal source which is connected to a wiring trace on the printed circuit board, which is soldered to the lead being tested. A capacitive test probe is placed on top of the component and connected to a capacitance measuring device. The signal source signal is capacitively coupled through the lead of the integrated circuit package being tested to the capacitive test probe, so if a predetermined capacitance is measured by the capacitance measuring device, the lead is connected to the circuit assembly. As the capacitances being measured are small, the capacitive test probe may include an amplifier, a shield or a buffer circuit to reduce stray capacitance.

Abstract: A capacitance point level switch includes a probe adapted to be disposed in a material containing vessel, the material having a capacitance value dependent upon its level in the vessel. An oscillator circuit develops a periodic signal at a select frequency. A reference network is driven by the oscillator and includes a reference capacitance for developing a periodic reference signal at the select frequency and phase displaced responsive to the reference capacitance. A probe network is driven by the oscillator and is connected to the probe to include the capacitance of the material for developing a periodic probe signal at the select frequency and phase displaced responsive to capacitance of the material. An output circuit is connected to the reference network and the probe network for developing a discrete output assuming a first or a second state according to the relative phase displacement of the periodic reference signal and the periodic probe signal.

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 a circuit are provided for detecting low level ionic currents. An ionization detection voltage is applied to a spark plug and a resulting output voltage signal is sent to a threshold device. The output voltage signal is developed by a low offset operational amplifier. First and second serially connected Zener diodes carry current in a normal diode direction when a spark event occurs and carry current in their Zener breakdown mode upon recovery from the spark event. A second operational amplifier and its associated feedback circuit generate a guard voltage which is applied to the junction of the two Zener diodes. The guard voltage is regulated to track the input voltage to the circuit at the cathode of the first diode. Because the guard voltage is essentially the same as the input voltage, there is no leakage current flow through the first diode.

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: Guarded capacitance probe structures are constructed with guard electrodes surrounding one or more sensor electrodes and ground electrodes or grounded surfaces surrounding the guard electrodes. In a one sensor embodiment, the probe utilizes an apertured sensor electrode and the guard electrode both surrounds the sensor electrode and fills the aperture. This embodiment is particularly useful for measuring particle concentration in a fluid suspension contained within a vessel or pipe. The portion of the guard electrode within the aperture of the sensor electrode prevents electric field lines from emanating from the sensor electrode into the fluid suspension and toward infinity. A two sensor embodiment of the probe is useful for measuring flow velocities of fluid suspensions through cross correlation of the outputs generated by each sensor.

Abstract: Conductive measuring electrodes, of a capacitive probe having a grounded rd electrode positioned therebetween shield a probe circuit, provides mutual capacitance measurements which way as a function of changes in impedance of dielectric material being monitored as it undergoes a curing process. The probe is positioned in non-embedded relation to the dielectric material to form a sensitivity region therein through which an electric field extends between the conductive measuring electrodes of the probe to establish said variable mutual capacitance measurements without extraneous influences.

Abstract: A pressure sensor measures pressure by measuring capacitance between two capacitive plates. Pressure change appears as a change in capacitance. Stray capacitance interferes with this measurement. The stray capacitance arises between the capacitor plates and surrounding material. Circuitry reduces stray capacitance by maintaining substantially no potential difference between a capacitor plate and surrounding material responsible for stray capacitance.

Abstract: Disclosed is a system for testing continuity that determines whether input and output leads of semiconductor components are present and properly soldered to a printed circuit board. The system includes a signal source stimulus which is connected to a wiring trace on the printed circuit board, which is soldered to the lead being tested. A capacitive test probe is placed on top of the component. The stimulus signal is capacitively coupled through the lead of the integrated circuit package being tested to the capacitive test probe, so if a predetermined signal level is detected by the capacitance test probe, the lead is connected to the circuit assembly. As the capacitances involved are small, the capacitive test probe includes an amplifier, a shield or guard and a buffer circuit to reduce stray fields pick up effects.

Abstract: The present invention is an improved ice sensor which is particularly effective in measuring and quantifying non-uniform, heterogeneous ice typically found on aircraft leading edges and top wing surfaces. In one embodiment, the ice sensor comprises a plurality of surface mounted capacitive sensors, each having a different electrode spacing. These sensors measure ice thickness by measuring the changes in capacitance of the flush electrode elements due to the presence of ice or water. Electronic guarding techniques are employed to minimize baseline and parasitic capacitances so as to decrease the noise level and thus increase the signal to noise ratio. Importantly, the use of guard electrodes for selective capacitive sensors also enables distributed capacitive measurements to be made over large or complex areas, independent of temperature or location, due to the capability of manipulating the electric field lines associated with the capacitive sensors.

Abstract: A capacitive position sensor has a scale (10), having hollow or raised topographical features, and a cursor (20) having an electrode array comprising at least two transmitting electrodes (21a, 21b) and at least one receiving electrode (21c) separated by shielding electrodes (21g). The coupling capacitances (Cac, Cbc) between transmitting and receiving cursor (20) electrodes are modified as a function of the position (x) of the scale topographic feature (11) relative to the cursor, the evaluation of the variation of the signals picked up by the receiving electrode permitting a precise measurement of the relative displacement between scale and cursor.

Abstract: Method and apparatus are described for obtaining information about the real and imaginary parts of permittivity in dielectric materials and relating this information to other properties of the materials.

Abstract: In order to measure a complex dielectric constant, a sample 8 enveloped by a ring 9 and two laminas 10 is inserted between parallel plate electrodes constituted by an exciting electrode 2 and a response electrode 3. Measuring data is obtained as a measuring value of the sample 8 itself because an operational circuit 21 removes parasitic effects of the ring 9 and the lamina 10. Dielectric characteristics of a fluid sample can be obtained readily and accurately without contaminating the electrodes.

Abstract: Apparatus for measuring the distance between a surface of a workpiece and a predetermined location of the type which measures the capacitance between the predetermined location and the workpiece surface and determines the distance corresponding to the measured capacitance. The apparatus includes a probe disposed at said predetermined location, the probe may be selectively excited to a known electric potential. A support assembly for supporting the workpiece is mounted on the apparatus for rotation relative to the probe. The support assembly is constructed to support the workpiece for rotation and to maintain the workpiece at a substantially constant electric potential. A grounding mechanism for grounding the support assembly includes a fixed grounding member and a liquid ground contact which engages the support assembly for maintaining electrical contact between the support assembly and the fixed grounding member as the support assembly rotates relative to the fixed grounding member.

Abstract: A capacitive type proximity sensor having substantial range and sensitivity between a machine and an intruding object in the immediate vicinity of the machine and having a steerable sensing field has an outer electrical conductor on the machine forming one electrode of a sensor capacitor, the other electrode is the object. The outer conductor is a thin sheet of conductive material with a pair (or more) of intermediate electrical conductors located between the outer conductor and the machine. The pair of intermediate electrical conductors are in close proximity to each other and together form a surface having a size substantially larger than the outer conductor to act as a shield for reducing the parasitic capacitance between the outer conductor and the machine and to steer the sensor field. The pair of intermediate conductors are thin sheets of conductive material substantially wider than the first conductor.

Abstract: An in-situ thickness monitoring/endpoint detection method and apparatus for chemical-mechanical polishing (CMP) of a dielectric layer on a top surface of a semiconductor wafer is disclosed. The apparatus comprises center and guard electrodes and associated electronic circuitry, including a high frequency, low voltage signal generating means, for converting a current which is inversely proportional to the dielectric layer thickness into a corresponding analog voltage. A position detection device triggers an analog-to-digital converter to convert the analog voltage into a digital signal while the wafer is located within a detection region as the wafer is being polished. A control means gathers the digital signals corresponding to the thickness data for processing and CMP device control.

Abstract: A capacitive position sensor has a scale (10), having hollow or raised topographical features, and a cursor (20) having an electrode array comprising at least two transmitting electrodes (21a, 21b) and at least one receiving electrode (21c) separated by shielding electrodes (21g). The coupling capacitances (Cac, Cbc) between transmitting and receiving cursor (20) electrodes are modified as a function of the position (x) of the scale topographic feature (11) relative to the cursor, the evaluation of the variation of the signals picked up by the receiving electrode permitting a precise measurement of the relative displacement between scale and cursor.

Abstract: A method and apparatus for sensing both axial and angular displacements of a collar relative to a shaft. The invention provides transmitting and receiving electrodes on the shaft and coupling electrodes on the collar. Displacements in the axial or angular directions vary the amount of signal conveyed between the electrodes relative to the quantities sought to be measured. An electronic package provides the appropriate signals and allows multiplexing of the data.

Abstract: A rotatable capacitance sensor for detecting film thickness of a moving film web, the rotatable sensor having a capacitive element arranged to contact the moving web film, the capacitive element electrically connected to projecting shaft ends of the rotatable sensor, resilient conductors urged against the respective shaft ends, and an electrical shield overlaying the resilient conductors and the rotatable shaft, to electrically isolate shaft wobble from the surrounding housing.

Abstract: Apparatus and methods for measuring the properties of a material by employing a driven electrode, a sensing electrode and a shunting electrode. The shunting electrode is disposed in proximity to the driven and sensing electrodes and functions to increase the sensitivity of electrical measurements made between the driven and sensing electrodes by influencing the coupling of the imposed electric field to the sensing electrode to a degree related to the properties of the material under test.

Abstract: A sensor which allows dielectric measurements to be made on a high temperature product such as a molten plastic flowing in a conduit. It comprises a ceramic cylinder with an interdigitated electrode capacitor patterned into the inside wall. Uses of the sensor include continuous determination of copolymer composition and polymer viscosity (molecular weight) in a completely non-obstructive manner.

Abstract: A capacitive sensor includes a plurality of individual condenser elements, each of which consist of a first, preferably circular, electrode and a second, preferably surrounding ring-shaped, electrode, which are mounted on one side of a nonconducting support. A common conductor is connected to each of the first electrodes of condenser elements. A signal can be detected separately from each of the condenser elements via conductors connected separately to the individual second electrodes. To increase the sensitivity and to avoid interference, the remote side of the support opposite to the one side is provided with a third additional electrode, which is at ground potential and also acts as a shield for interfering couplings. The sensor is used for measurement of the fuel film thickness in the intake of an internal combustion engine.

Abstract: A three-axis velocity probe system for determining three-axis positional velocities of small particles in fluidized bed systems and similar applications. This system has a sensor head containing four closely-spaced sensing electrodes of small wires that have flat ends to establish a two axis plane, e.g. a X-Y plane. Two of the sensing electrodes are positioned along one of the axes and the other two are along the second axis. These four sensing electrodes are surrounded by a guard electrode, and the outer surface is a ground electrode and support member for the sensing head. The electrodes are excited by, for example, sinusoidal voltage having a peak-to-peak voltage of up to 500 volts at a frequency of 2 MHz. Capacitive currents flowing between the four sensing electrodes and the ground electrode are influenced by the presence and position of a particle passing the sensing head.