Abstract: A.C. current is conducted through geological formations separating two cased wells in an oil field undergoing enhanced oil recovery operations such as water flooding operations. Methods and apparatus are disclosed to measure the current leakage conducted into a geological formation from within a first cased well that is responsive to fluids injected into formation from a second cased well during the enhanced oil production activities. The current leakage and apparent resistivity measured within the first cased well are responsive to fluids injected into formation from the second cased well provided the distance of separation between the two cased wells is less than, or on the order of, a Characteristic Length appropriate for the problem.

Abstract: Terrain resistivity is mapped by collecting data as to the vertical magnetic field ratio along a survey line by VLF survey techniques, and precision integrating rather than differentiating the data obtained. The received VLF signal is demodulated and low-pass filtered in a manner such as to preserve the DC component of the demodulated signal, and is then digitized and spatially integrated to obtain pseudo-resistivity readings along the survey line.

Abstract: A SQUID package includes a layered SQUID base and a SQUID mounted upon the base. The SQUID base is formed as a first substrate layer of an electrically insulating material, a shielding layer of a material that is superconducting at the SQUID operating temperature overlying the first substrate layer, and a second substrate layer of an electrically insulating material overlying the shielding layer. The shielding layer protects the SQUID from dc and ac interference such as magnetic and electrical fields, which would otherwise interfere with its operation. Related components such as input and output circuitry can be mounted on the base. An input coil used to detect magnetic fields can also be placed on the base, but in that case the shielding layer is made to cover only a portion of the SQUID base, and the input coil is positioned over the portion of the base that has no shielding layer.

Abstract: A highly sensitive magnetic field detecting system includes a DC superconducting quantum interference device (DC SQUID) for detecting a magnetic field to produce a signal voltage, and a flux locked loop (F.L.L.) circuit device for driving the DC SQUID. A phase detecting circuit forming part of the F.L.L. circuit device is composed of two phase detecting circuits having different phases to be detected. By adding the individual output signals of the two phase detecting circuits, the outputs can be unvaried at a phase difference equal to that of the detected phases of the two detecting circuits. The added signal is also unvaried with respect to the phase variations of the detected signal so that the metering procedures can be simplified without any necessity for phase adjustment. Further, the output signals obtained can be stable relative to the phase drifts of the signal to be transmitted from the DC SQUID to improve the metering precision.

Abstract: The radiator and the sensor each comprise three pairs of Helmholtz coils which are disposed along three orthogonal axes respectively. The coils are wound in pairs of grooves which have different depths and are recessed in a cubic support. The radiator and sensor are particularly useful for helmet-type viewfinders.

Abstract: The magnetic encoder of the present invention includes a magnetic signal generating drum having plural magnetic pole lines respectively having different magnetization pitches. Magnetic signals are repeatedly generated from the plural magnetic pole lines. A magnetic sensor is provided which includes plural magnetic resistant effect elements for converting the respective magnetic signals generated from the plural magnetic pole lines into electric signals. The plural magnetic resistant effect elements respectively confront the plural magnetic pole lines and output electric signals of different pulse numbers in accordance with incident magnetic signals. The magnetic signals generated from the plural magnetic poles lines and incident on the magnetic resistant effect elements are less that an anisotropic magnetic field level of the respective magnetic resistant effect elements.

Abstract: A process and an apparatus for measuring the biocurrent distribution call for initially assuming a number of multiple currents which is more than the number of isolated currents possibly existing in a living body and calculating the virtual magnetic field created by the assumed currents at actual measuring points. The estimated location and current vectors of said assumed currents are consecutively changed to decrease the difference between said virtual and actual magnetic fields so that the estimated location and current vectors of the assumed currents having the number corresponding to the true isolated currents substantially approximate the true values and the estimates of the other assumed currents approximate zero. This enables the biocurrent distribution to be exactly determined even when the number of isolated currents is not preliminarily known.

Abstract: A system for identifying and measuring stress at specific locations within a ferromagnetic material by the production and detection of Barkhausen noise during magnetization of the material. The method involves introducing into the material a time varying magnetic field component and a spatially-varying magnetic field component that in combination create a singular zero magnetic flux element within the material that "sweeps" from one position within the material to another and back. By time-gating the detected acoustic Barkhausen signal that results as this zero flux element moves within the material, the signal is isolated as having been generated at a specific depth within the specimen. Since the level of Barkhausen noise varies with stress, a tomographic mapping of stress is obtained for the interior of the ferromagnetic specimen. Through the use of a computer, a three dimensional map of stress in the ferromagnetic material is obtained.

Abstract: A micromechanical sensor comprises a support, a micromechanical element that is movable relative to the support under the application of a stimulus, and a transducer. The transducer comprises a first component carried by the micromechanical element and movable therewith, and a second component stationary relative to the support. One of the first and second transducer components is a member for establishing a magnetic field and the other of the first and second transducer components is a SQUID positioned in the magnetic field for detecting variation in the magnetic field due to relative movement of the micromechanical element and the support.

Abstract: A superconducting pickup coil is provided for interlinking with an unknown magnetic flux and causing an induction current to flow. A superconducting detector is provided magnetically coupled with the superconducting pickup coil for producing output voltage pulses in response to the unknown magnetic flux. A superconducting feedback circuit is provided connected to the superconducting detector for receiving the output voltage pulses therefrom and feeding back a feedback magnetic flux to the superconducting pickup coil in response to each output voltage pulse such that the feedback magnetic flux counteracts the unknown magnetic flux. A resistance fixture is provided in the vicinity of the superconducting pickup coil for causing a transition in a part of the superconducting pickup coil from a superconducting state to a normal conducting state in response to the drive current.

Abstract: A vibration detector for sensing imbalance of a part in a balancing machine uses an eddy current proximity detector for sensing vibration movement of a portion of the machine. To prevent spurious signals due to magnetic fields varying at the part rotation frequency, a mu-metal can is secured to the vibrating portion of the machine, an electrically conductive coupon is attached inside the can for vibrating movement therewith, and the proximity detector is spaced from the coupon by a small gap for producing AC signals representing the vibration amplitude.

Abstract: A joystick controller employs differential pairs of electronic sensors to detect the direction of displacement of the joystick shaft and a single electronic sensor to detect the magnitude of the displacement. The differential pairs of sensors output signals representative of the direction of the displacement of the joystick shaft from a datum. The single sensor outputs signals having a magnitude representative of the magnitude of the displacement. A controller uses the output signals to control a dependent device. In one embodiment, the controller compares the sensor output signals to predetermined threshold values and ignores movements of the shaft which cause the sensors to generate output signals having magnitudes below the threshold values.

Abstract: A method and device are shown for locating the longitudinal axis of a subterranean branch pipe from a main pipe. A magnetic field emitter is mounted in the branch pipe so that it radiates magnetic lines of force along the branch pipe and into the main pipe. The axis of the branch pipe is located by detecting the primary line of the magnetic flux emitted from the emitter using a location device which is moveable within the main pipe. By locating the axis of the branch pipe, a hole registering with the branch can be cut in a lining within the main pipe from which the branch pipe leads.

Abstract: A stud finder includes a magnetic subassembly for detecting the presence of a ferrous metal object, such as the head of a nail or screw, in a wall, with the magnetic subassembly being mounted at one end of a base member. A level vial is mounted at the other end of the base member, and a slot is formed in the base member between the magnetic subassembly and the level vial. When the base member is placed against a wall and the presence of a stud is detected by the magnetic subassembly, the base member is moved to a position in which the level vial indicates level. The slot has its longitudinal axis oriented perpendicular to the longitudinal axis of the level vial, so that the user can place a vertical mark on the wall through the slot. The slot is oriented so as to be in vertical alignment with the nail or screw head, when the base member is moved such that the magnetic subassembly is directly over the nail or screw head.

Abstract: The cross coil type meter has a magnet rotor and a stopper plate inside a coil bobbin. The magnet rotor is driven by a combined magnetic field produced by a cross coil wound on the coil bobbin. A pointer on a dial plate is attached to the magnet rotor's shaft so that it can indicate the magnitude of a measured quantity. The stopper plate engages with the magnet rotor to stop the pointer at a zero position on the dial plate. But when due to some assembly errors the stop position of the pointer and the zero position on the dial plate do not agree, the position of engagement between the magnet rotor and the stopper plate can be adjusted by manipulating the stopper plate from outside until the two positions agree.

Abstract: The method evaluates borehole formations using corrected formation resistivity logs obtained from a formation evaluation tool. In accordance with the present invention the method corrects the error in the amplitude ratio resistivity curve R.sub.ar and the phase difference resistivity curve R.sub.pd thereby providing a more accurate formation resistivity log. The method of this invention employs a low frequency mixing law such as Archie's equation in combination with a high frequency mixing law such as Complex Refractive Index Method (CRIM) to correct the measurements of wave propagation type formation evaluation tools for the effects of the dielectric constant on the tool's measured parameters.

Abstract: An RPM and voltage indicator is used to check the operating speed and voltage output of a generator set. The device is used to verify the proper operation of a generator set or any auxiliary power unit, such as a DC to AC invertor, and further functions as a tool to make necessary adjustments to a governor or frequency control of any such generator set or auxiliary power unit.

Abstract: Apparatus for developing a series of square-wave pulses from an alternating voltage that is generated in the pick-up coil of a variable reluctance sensor that is associated with a slotted wheel that is driven by the crankshaft of an internal combustion engine. The system has an adaptive control which comprises a peak detector, a capacitor and a voltage comparator. The capacitor is charged to a peak voltage that corresponds to the peak value fo the positive half-cycles of the alternating voltage. The comparator is connected to compare the peak voltage and a voltage that corresponds to the magnitude of the positive half-cycles. A diode is connected between the pick-up coil and the peak detector which prevents charging of the capacitor and accordingly prevents adaptive control until the voltage induced in the pick-up coil is high enough to cause the diode to conduct in the forward direction.

Abstract: An absolute position detector samples and outputs a digital value of absolute position data of an object of detection at each predetermined sampling timing. An interpolation circuit interpolates between position data of different sampling timings provided by the absolute position detector, thereby to produce absolute position data at close intervals. Such arrangement produces absolute position data with a time resolution which is finer than the period of the sampling timing. A further circuit produces an incremental pulse train on the basis of the output of the interpolation circuit in correspondence to change in a value of interpolation for each interpolation step.

Abstract: Method and apparatus for non-destructively monitoring the thickness and uniformity of electrically conductive coatings (12) that have been deposited upon optical waveguide fibers (10). The monitoring may be performed while coated fiber (22) is at rest or while it is in motion. Physical contact with fiber (22) is not required. Monitoring is accomplished by feeding coated fibers (22) through an inductive coil (24) while simultaneously measuring an electrical value that is dependent upon the electrical resistance of conductive coating (10) then passing through inductive coil (24). The electrical value measured for a given section of coated fiber (22) becomes indicative of the coating thickness and uniformity of the coating about optical waveguide fiber (10) by correlating the electrical value measured with previously measured electrical values generated by coated fibers having coatings of known thicknesses and having no bald spots or other non-uniformities.