Abstract: A stochastic excitation, SQUID detection system for determining the frequency response of a sample. A pair of counterwound detection coils are adjacent to an excitation coil. The sample is selectively placed in one of the detection coils for taking measurements. The SQUID sensor is a broadband, high sensitivity device which enables the frequency response of the sample to be determined over a wide bandwidth with a single measurement.

Abstract: Apparatus for simultaneously generating and measuring a triboelectric charge generated on a strip of flexible sample material includes a stationary rod of insulating material, driving motor for the sample material adapted to move the sample material in frictional contact with the rod, a support rod for maintaining a surface of the sample material in straight-line tangential relationship with the rod, and a static-charge sensor disposed between the stationary rod and the support rod and spaced from the surface of the sample material for measuring a charge on the surface in cooperation with a voltage-measuring device.

Abstract: A method and apparatus for inserting an eddy current hole probe into a hole specimen and automatically moving the probe in two orthogonal (X, Y) directions in response to the impedance change of an eddy current coil located in the probe as a function of distance from the surface of the hole. The probe is centered in the hole by a system controller which operates to minimize the composite deviation value of the coil impedance. The diameter of the hole is then determined from the average impedance measurement. Following this, a plot of the hole eccentricity is generated by determining the impedance deviation from the average coil impedance value as a function of the angular rotation of the probe in the hole. Measurements of the hole eccentricity for a plurality of hole depths provides an indication of the hole eccentricity profile.

Abstract: Measurement-while-drilling apparatus is disclosed for determining the resistivity of formations surrounding an earth borehole. An electrically conductive metal body, such as a drill collar on a drill string, is movable through the borehole. A transmitting toroidal coil antenna is disposed on the body and is energized to induce a current which travels in a path that includes the body and the formations. An electrode is disposed on the body, and an electrical signal resulting from said current is measured at the electrode to obtain an indication of the resistivity of the formations. In a disclosed embodiment, one or more electrodes can be mounted on a blade that is mechanically coupled to the body.

Abstract: A sensor for detecting faults in a magnetized ferrous body which has a first ferrite disc having at least two opposed sides, a pair of Hall Effect semiconductors, the Hall Effect semiconductors being affixed to opposite sides of said ferrite disc and a pair of ferrite discs, each ferrite disc of said pair of ferrite discs being affixed to a side of each of said Hall Effect semiconductors opposite the side of said Hall Effect semiconductors which is affixed to the first ferrite disc.

Abstract: A locator/monitor for locating a boring tool and monitoring the progress of the tool for control purposes. The locator/monitor is used in expedited locating methodology and straightforward calibration techniques of the present invention. A durable and cost effective pitch sensor is also provided by the present invention. In addition, the present invention provides a slotted transmitter housing formed of an electrically conductive material, where the magnetic field generated by the transmitter is capable of penetrating to the surface.

Abstract: A magnetic sensor for the collection and measurement of ferrous particles through the use of an electronic tuned circuit is disclosed. The sensor contains an electrical inductance coil along with an integral magnet to attract ferrous particles suspended in the fluid. The ferrous particles collecting on the magnetic surface of the sensor causes a change in the inductance of the integral coil which is measured by an electronic circuit. The electronic circuit operating in conjunction with the sensor utilizes a series resonant circuit. A measurement of the voltage across the series resonant circuit is responsive to changes in temperature of the inductance coil. A microprocessor is used to determine the change in period of the resonant oscillation with change in inductance of the coil. The microprocessor uses the data on temperature variation to correct the observed change in oscillator period for the effects of temperature.

Abstract: A simulated load circuit for measuring the impedance of the arc discharge of an electrodeless discharge lamp of the type having an arc tube and an excitation coil for exciting the arc discharge in an ionizable fill contained therein includes: a secondary coil spaced apart from the excitation coil by a distance which is varied in order to vary the coupling coefficient between the secondary coil and the excitation coil; a fixed load resistance coupled to the secondary coil; and a variable matching network coupled in series or parallel with the load resistance, the impedance of the matching network being varied in order to vary the ratio of reactance to resistance of the load circuit. The distance between the secondary coil and the excitation coil is varied, and the impedance of the matching network is varied, until the input impedance of the load circuit is substantially equivalent to the operating impedance of the lamp.

Abstract: An apparatus for detecting an electrostatic force in a solution includes a sample and a cantilever. An end of the cantilever is conductive and has voltage applied to it. The apparatus detects electrostatic interaction caused by functional groups of target molecules in the solution.

Abstract: A variable area flowmeter employing a vertical tube containing a displaceable magnet and a closed-loop magnetic detection circuit. The closed-loop magnetic detection circuit includes first and second magnetic cores each having a sense coil and a compensation coil. The sense coil provides an output related to magnetic field strength. With a feedback technique, the compensation coil compensates for the magnetic field through the sense coil. Field strength is determined by monitoring feedback. Displacement of the displaceable magnet is determined using information from the first and second magnetic cores. The detection circuit produces an output proportional to the position of the magnet within the tube. This output is translated into fluid flow.

Abstract: The grain structure of electrical steel strip is tested by inducing a magnetic flux field into the strip by pole pieces at opposite sides of a permanent magnet. A magnetic detector head between the pole pieces responds to the leakage of flux as the steel strip and/or magnetic detection undergoes relative movement. A recorder is used to identify banding and mixed grain structures which cause a smaller flux leakage amplitude than larger desired grains.

Abstract: An inductive position indicator has an exciter coil for generating a magnetic flux, a measurement coil arrangement, and a flux guide of ferromagnetic material which provides for the magnetic flux a closed measurement path which includes at least one gap, in the region of which the measurement coil arrangement is so positioned that the magnetic flux passing therethrough changes in dependence on the position to be monitored. To improve the fidelity of the characteristic and enhance measurement accuracy, the flux guide provides at least one further closed compensating path which carries the magnetic flux passing therethrough, past the magnetic coil arrangement. When there are two mutually adjacent measurement coils through the surfaces of which the measurement flux can pass in a variable fashion and the output signal difference of which is included in the position signal, the surfaces enclosed by the measurement coils have at least one common edge portion over which the measurement flux can move.

Abstract: A magnetic inspection device for non-destructively testing elongated objects such as large diameter wire cables is constructed with a number of flux carrying components that are assembled and disassembled in sections with a magnetic flux detector for detecting the loss of metallic cross-section and local discontinuities in the cable. The inspection device is moved bodily along a cable during the inspection process and in another embodiment the flux detector itself is the only component movable along the cable. Jack screws are utilized to mechanically separate or bring together the flux carrying components which are normally attracted to one another by powerful magnetic forces. Draw screws are also employed to pull together flux carrying components which are naturally repulsed from one another by the magnetic forces. Alignment pins are utilized to guide the components together in predetermined positional relationships during assembly processes.

Abstract: A thin film dc SQUID and its driving electronic circuitry configured with very high symmetry, having a SQUID loop formed with four holes (24, 24, 26, 27) at the respective ends of crossed slits (22, 23). Each of these holes forms a single turn secondary coil for symmetrically arranged pairs of modulation coils and signal coils. The geometrical placement of the modulation coils with respect to the signal coils results in a device which nominally has no mutual inductance between the two groups of coils when the SQUID is biased for normal operation. The external driving circuit (75-85) is configured to preserve the highly balanced nature of the SQUID and forces an equal magnitude of current to flow in all four of the bias leads.

Abstract: An eddy current device for inspecting a component includes an eddy current array circuit having respective pluralities of drive and sense elements and having an active face for positioning on a surface of the component during the inspection operation. A backing is disposed on a face of the eddy current array circuit opposite to the active face for concentrating an electromagnetic flux from the eddy current array circuit into the component when each of the plurality of drive elements is being energized. A mechanical arrangement is provided for supporting and deploying the backing and the array circuit to substantially conform with the surface portion under inspection and to cause each of the pluralities of drive and sense elements to be maintained at their respective substantially constant distances from the inspection surface during scanning, preferably at a controlled rate of scan.

Abstract: A sensing coil arrangement including a pair of sensing coils connected in opposition is used to measure AC susceptibility and, using sample movement and a DC magnetization field source, also to sense signals for absolute DC moment measurements. Since the same sensing coil arrangement is used for both AC and DC measurements, the measurements can be made successively in situ without removing the sample from a sample space (e.g., within a cryogenic chamber). This is a big advantage, because the changed conditions associated with removing and replacing a sample between measurements can cause confusing, uncorrelated results. A high speed voltmeter is used to perform the signal analysis for the moment measurement. The system can be configured to yield high resolution DC moment measurements to 25 ppm and sensitivities to better than 5.times.10.sup.-5 emu.

Abstract: A ratio measuring apparatus which allows continuous monitoring of two or more digital signals so as to yield an indication of the ratio of frequencies between such signals for use in process control. The apparatus includes a channel transfer circuit adapted to rotate inputs or outputs in the apparatus for logical orientation thereof. The apparatus further includes primary and secondary counters, each of which is coupled to an input signal for processing thereof. These counters operate relative to one another for logical processing of the input signals to yield ratio information. The primary counter is coupled to a data latch system, acting as a temporary memory storage for the measured ratio information. The data latch may also be coupled to a display means.

Abstract: A position sensor having two magnetically sensitive devices associated with a magnet. The sensor is disposable proximate a rotatable member having at least one discontinuity in its surface. The two magnetically sensitive devices, such as Hall effect transducers, each provide output signals that represent the direction and magnitude of the magnetic field in which its respective transducer is disposed. An algebraic sum of the first and second output signals from the magnetically sensitive devices is provided as an indication of the location of the rotatable member that is disposed proximate the sensor.

Abstract: A noncontacting displacement measuring system therefor a sensor (2) with a housing (11), at least one coil (1) accommodated in the sensor housing (11) and an embedding substance (13) for anchoring the coil (1), and further therefor an electronic supply/evaluation unit, is designed such that the influence of fluids and solids with a high dielectric constant on the measured values is large eliminated. To this end, a shield (15) is provided on the measuring side (8) of the sensor (2), which is at least largely impervious to electric field lines (9) emanating from the coil (1), but largely permeable to electromagnetic field lines emanating from the coil (1).

Abstract: An electromagnetically complete field vector field probe has a set of three dipoles extending along three mutually perpendicular axes, and three loops situated in mutually orthogonal planes defined by different pairs of said axes. The dipoles and loops are all disposed about a common center. Each dipole has a central element and two end elements, separated by gaps. Each loop has four conducting elements each extending from a point adjacent to one of the three axes to a point adjacent to another of the three axes. The conducting elements of each loop are separated from one another by gaps at the axes, so that each gap of each loop is substantially coincident with a gap of another loop and with a gap of a dipole. Coaxial lines extending through the central conducting elements of the dipoles are connected directly to the ends of the loop elements and need not extend through parts of the loop elements themselves.