Abstract: An analog angle encoder includes a non-magnetic stator which is cup-shaped, having a central post carrying at least one magnetosensitive device, and further including a rotor in the form of a ring captured by the stator, the rotor carrying at least one permanent magnet, wherein the rotor is rotatable relative to the stator. As the rotor rotates relative to the stator, the angle of the incident magnetic field changes relative to the magnetosensitive device, thereby causing the output from the device to vary sinusoidally with angular position. It is preferred to use magnetic configurations other than simple six sided magnets in order to achieve a more uniform magnetic field at the magnetosensitive device, as for example by utilizing cylindrical magnets, arcuate (concave faced) magnets, flat ferromagnetic layer pole pieces, arcuate (concave faced) ferromagnetic layer pole pieces, and ferromagnetic return paths.

Abstract: A method of sensing the position of a first element with respect to a second element is disclosed, the first element being movable with respect to the second. The method comprises: (a) fixing a first magnetic marker to said first element; (b) fixing a second magnetic marker to said second element; (c) sensing the positions of the two markers by a remote magnetic sensing technique. Optionally, a third magnetic marker may be used, the second and third markers then preferably being located at the extremes of travel of said first element. The method may be used to determine linear or angular relationships.

Abstract: A compact magnetic field exposure sensor and analysis system suitable for use in the calibration of induction heating processes such as foil cap sealing or the heat treatment of metals. The compact sensor is a self-contained sensing coil, and signal storage, processing and/or transmittingcomponents that can be configured to suit narrow-mouth containers. Detected and/or processed signals can be transmitted to remote storage, processing and/or display subsystems from the sensor.

Abstract: A method for compensating mechanical stresses in measuring the magnetic field strength by Hall sensors is disclosed. It is proceeded in a manner that the electric resistance and/or a measuring quantity proportional to the electric resistance of the Hall sensor is determined in at least two different directions, that the mean value of the determined resistances and/or measuring quantities proportional thereto is calculated, and that the current conducted through the Hall sensor is chosen to be proportional to the mean value calculated.

Abstract: The present invention provides a power frequency, i.e., time-varying, magnetic field (PF-NF) detector system for characterizing the operational condition of a remote facility responsive to time-varying magnetic fields generated by electrical transmission lines associated with the remote facility. The PF-MF detector system advantageously includes a PF-MF sensor which generates N time-varying magnetic field data sets, and a PF-MF analyzer which generates an operational condition assessment responsive to the N time-varying magnetic field data sets, wherein N is an integer greater than or equal to 1. Additionally, the PF-MF detector system includes an accumulator which stores and forwards the N time-varying magnetic field data sets to the PF-MF analyzer via a communications channel. A method for characterizing the operational condition of inaccessible electrical equipment responsive to the time-varying magnetic field generated by a transmission line are also described.

Abstract: A rotation sensor (10) provided with a first rotor (11) fixed to a predetermined position in the axial direction of the shaft, a second rotor (12) fixed to the shaft (5) adjoining the first rotor, and a magnetic material core (13) having a resonance coil (13c) arranged around the first rotor and forming a magnetic circuit working with the first rotor. The first rotor (11) is formed by a magnetic material comprised of an insulator, an irregular magnetic field is formed with the magnetic material core, and the second rotor (12) is provided with a conductor cutting across areas of different intensities of the irregular magnetic field in accordance with the difference of the angle of rotation when a difference in the angle of relative rotation occurs at a shaft position where the first rotor is fixed and a shaft position where the second rotor is fixed.

Abstract: A time/analog converter for adjusting the zero point and amplification of the output characteristic of a sensor includes an integrator whose output is connected to the input of a holding member. A reference voltage and the output voltage of the holding member occur at the input of the integrator. A control means actuates switches connecting the integrator to the holding member and applying the reference voltage and the output voltage to the input of the integrator so that the reference voltage is at the integrator input for a first time interval and the holding member output voltage is at the integrator input for a second time interval. The integrator output voltage is applied to the holding member for a third time interval. A controllable pulse shaper is connected to one of the switches and can close it for a required time interval. A related method is also described.

Abstract: This invention is directed to a downhole method and apparatus for simultaneously determining the horizontal resistivity, vertical resistivity, and relative dip angle for anisotropic earth formations. The present invention accomplishes this objective by using an antenna configuration in which a transmitter antenna and a receiver antenna are oriented in non-parallel planes such that the vertical resistivity and the relative dip angle are decoupled. Preferably, either the transmitter or the receiver is mounted in a conventional orientation in a first plane that is normal to the tool axis, and the other antenna is mounted in a second plane that is not parallel to the first plane. This invention also relates to a method and apparatus for steering a downhole tool during a drilling operation in order to maintain the borehole within a desired earth formation.

Abstract: Inductive sensor for non-contact detection of discontinuities of a conductive or ferromagnetic target for determination of target position, movement and speed, or generally of a magnetic image, including a plurality of receiving secondary windings associated with each exciting primary winding, configured to obtain electric signals optimized as a function of the discontinuities of the target. The sensor, combined with a suitable electric measuring circuit, allows global analysis of the signals provided by the secondary windings and configuration of a network in accordance with a predefined selection. An adaptive circuit allows auto-calibration of the sensor.

Abstract: A new method and apparatus for detecting and measuring the level of metal present on the surface of a substrate is achieved. Energy, in the form of rf or light or microwave energy, is directed at the surface of a wafer, the reflected energy or the energy that passes through the semiconductor substrate is captured and analyzed for energy level and/or frequency content. Based on this analysis conclusions can be drawn regarding presence and type of metal on the surface of the wafer. Furthermore, by inclusion of metal within the resonating circuit of an rf generator changes the frequency of the vibration and therefore detects the presence of metal.

Abstract: A magnetic rotational position sensor for sensing each rotational position of a control shaft about a first axis over a definable range of rotation. The position sensor generally includes a magnetic circuit and a pair of magnetic flux sensors. The magnetic circuit is comprised of a ring pole piece defining an air gap area and a magnet disposed within the air gap area. The ring pole piece and the magnet cooperate to produce a magnetic field within the air gap area. The magnetic circuit is adjoined to the control shaft to synchronously rotate the magnetic field about a second axis. The pair of magnetic flux sensors are disposed within the magnetic field to sense each rotational position of the control shaft as the control shaft is rotated about the first axis over the definable range of rotation.

Abstract: A system for testing the read/write head elements of a head stack assembly (“HSA”). A completed HSA is placed in the test apparatus. Test probes are aligned and placed in electrical contact with the electrical leads coming from each head element, between the head elements and the preamplifier. The HSA is then placed in a changing magnetic field. A low frequency magnetic field can be applied to test the head elements. The changing magnetic field induces electrical signals within the head elements. By analyzing these electrical signals, the condition and characteristics of the each head element can be determined.

Abstract: The invention relates to a method for determining the position and/or the speed of motion of a control element which can be moved back and forth between a first and second switching position. According to said method, an immersion body which is connected to the control element is guided through at least one stationary plunger coil, synchronously with the motion of said control element. The voltage that is generated as a result of the immersion body moving in relation to a permanent magnet and/or a permanent magnet moving in relation to the plunger coil is detected as a signal for the speed of motion of the control clement. The changes in impedance and or a current that are caused as a result of the movement of the immersion body in the plunger coil are detected as a signal for the position of the control element.

Abstract: A method and apparatus for imaging deep underground objects utilizes the application of a spectral regularization routine that is applied to measured data prior to the application of an inversion routine to measured surface impedances to map subsurface conductivity. Specifically, measurement of magnetic and electric fields is conducted utilizing sensors at a measurement site, a processor is used to generate either resistivity or conductivity data based on the measurements of the sensors, the processor then performs the spectral regularization routine and an inversion routine to generate data that can be utilized to identify underground targets. The spectral regularization routine and inversion routine can either be processed separately (decoupled) or together. The measurements of the magnetic and electric fields are preferably made under the assumption of the presence of a plane wave at the measurement site.

Abstract: The sheet resistance meter has: a coil which produces a magnetic field; a sensor head provided to enable the magnetic field to induce eddy currents in a thin film formed on a substrate so that the lines of a magnetic force exerted by the magnetic field extend on one side of the substrate; a control device for detecting the sheet resistance of the thin film according to a variation of the magnetic field caused by the eddy currents; a capacitor for achieving resonance with the coil; and a groove section, a primary air port, an auxiliary air port, and a side air port, provided in the sensor head, for controlling the temperature of the coil. The arrangement stabilizes results of the measurement of a sheet resistance by a sheet resistance meter of a one-sided eddy current detection type when it is used continuously.

Abstract: An eddy current sensor including an arrangement for generating a first magenetic flux, which is essentially directed vertically with respect to a moved body, a detector coil for detecting an eddy field in the moved body and a second arrangement which generates a further adjustable magnetic flux, which is superimposed on the first magnetic flux to form a resultant magnetic flux.

Abstract: A method and system for determining the location of a microseismic event is disclosed. An electromagnetic sensor measures the electromagnetic energy which is caused by a microseismic event. Seismic data from the microseismic event is measured and recorded using plurality of ground motion sensors. The time at which microseismic event occurred is estimated based at least in part on the time at which electromagnetic energy caused by the microseismic event is received by the electromagnetic sensor. The location of said source of the microseismic event is determined using the estimated occurrence time and the time at which the seismic energy arrived at the ground motion sensors. A method of triggering a seismic recording device is also disclosed. The electromagnetic energy from a microseismic event is measured and recorded using an electromagnetic sensor. The time at which the microseismic event occurred is estimated based on the measured electromagnetic energy.

Abstract: A magnetic field measuring apparatus for precise cancellation of environmental noise includes a plurality of first SQUID gradiometers to detect noise and biomagnetic fields, a plurality of second SQUID gradiometers to detect noise, a driving circuit to drive these gradiometers, and a computer to execute signal processing after collecting the signals detected by these gradiometers. First and second SQUID gradiometers are provided which include first-order gradient pickup coils with the baselines formed by the coils of second gradiometers being shorter than those of first gradiometers. The apparatus cancels noise, from detected biomagnetic signal waveforms, caused by variant noise cancellation rates of the coils of first gradiometers, different baselines of the coils of second gradiometers, and the frequency property of a magnetically shielded room in which the apparatus is installed.

Abstract: A pipeline inspection vehicle which can be towed through a pipeline via a cable. The vehicle includes a power unit, a master processor module, and a coil which generates an eddy current field which passes along the pipe. The resultant field is detected by a master sensor ring and slave sensor ring. Information on an amplitude and phase of the detected field together with vehicle orientation information is sent to a base station which has a computer. A distance encoder also is provided to assist in locating the position of any detected faults.

Abstract: A rotational angle detecting device includes a rotation detecting section for outputting sinusoidal first and second detection signals as a result of the rotation of a rotor connected to a rotary member, a storage section for updating and storing the first and second detection signals, and a controlling section. The first and second detection signals have constant amplitudes, have the same periods, and have wavelengths which are output of phase. The controlling section compares the amplitude values of most recent first and second detection signals output from the rotation detecting section, and determines whether or not the amplitude values fall within proper ranges. When the controlling section determines that they fall within the proper ranges, a piece of detection information which is created based on the most recent first and second detection signals is supplied to a controller.