Abstract: A system for inspecting a tubular may comprise an electromagnetic (EM) logging tool and information handling system. The EM logging tool may further include a mandrel, one or more sensor pads attached to the mandrel by one or more extendable arms, and one or more partial saturation eddy current sensors disposed on each of the one or more sensor pads.

Abstract: Methods and devices used to calibrate EM corrosion detection tools may estimate the effects of the presence of a core on measurements to enable more accurate corrosion detection in the well line. The methods may involve sending voltages to a core of a well tool disposed in the well line to obtain signals while the core is in a saturated and unsaturated state. Subsequent measurements using the core may be calibrated using a constant resulting from the division of the signals achieved at the core in the saturated and unsaturated states.

Abstract: A method for performing operations in a well comprises sensing a condition at, adjacent, or within a wellhead arrangement located at an opening of the well and performing a safety procedure in response to the sensed condition to improve the safety of the well operations. The method may comprise sensing the condition when a tool is located at, adjacent to, or within the wellhead arrangement. The sensed condition may be associated with a status of the tool. The sensed condition may be associated with an emission, field or signal transmitted to and/or from the tool, extending to and/or from the tool, and/or coupled to and/or from the tool. Performing the safety procedure may comprise controlling a position or status of the tool or controlling an environment at, adjacent to, or within the wellhead arrangement.

Abstract: A method for configuring a system for recognizing a class of objects of variable morphology, comprising providing a machine learning system with an initial data set to recognize instances of objects of the class in a sequence of images of a target scene; providing a three-dimensional model specific to the class of objects, the morphology of which can be defined by a set of parameters; acquiring a sequence of images of the scene using a camera; recognizing image instances of objects of the class in the acquired image sequence; conforming the generic three-dimensional model to recognized image instances; storing variation ranges of the parameters resulting from the conformations of the generic model; synthesizing multiple three-dimensional objects from the generic model by varying the parameters in the stored variation ranges; and complementing the data set of the learning system with projections of the synthesized objects in the plane of the images.

Abstract: Direct field cancelation with optional receive antenna compensation is provided in at least some gradient induction logging tool embodiments. Illustrative embodiments include a spatial gradient antenna arrangement having multiple spatially-separated multi-component coil antennas and a multi-component coil antenna having bucking coils that cancel the effects of both the direct field and the gradient of the direct field on the receive signal. Other tool embodiments include a multi-component coil antenna and a spatial gradient antenna arrangement having spatially separated multi-component coil antennas with bucking coils that cancel the effects of both the direct field and the gradient of the direct field on the receive signal. Those embodiments employing a spatial gradient antenna arrangement for receiving may further be configured to provide compensated measurements by combining measurements from rotated orientations of the spatial gradient antenna.

Abstract: Various disclosed borehole imaging tools and methods provide an improved high-resolution electrode configuration suitable for imaging in both water-based and oil-based muds. In at least some embodiments, the imaging tools employ a unitary conductive body to provide a wall-contacting face with grooves that define multiple sensing surfaces. Toroids may be seated in the grooves around each sensing surface for measuring the current flow through each sensing surface. Such placement enables a nearly ideal equipotential surface to be maintained and a straightforward “full coverage” electrode configuration due to a minimal electrode separation. Moreover, the disclosed configuration promises robust and reliable performance in the hostile conditions often experienced by logging while drilling (LWD) tools. This wall-contacting face can be provided on an extendable sensor pad or embedded on the outer surface of a LWD stabilizer fin.

Abstract: A downhole tool, in some embodiments, comprises a casing collar locator (CCL) to generate a signal that indicates the presence of a casing discontinuity; and a modulator, coupled to the CCL, to modulate fixed-wavelength light in a fiber optic cable based on said signal.

Abstract: A technique facilitates prediction of run life. Data relating to a pipe defect is provided to a data processing system for comparison to stored data regarding defects. Additionally, data regarding fatigue life accumulation is stored on the data processing system as it relates to fatigue life of the pipe based on the number of cycles to failure of the pipe without the presence of the defect. The number of cycles experienced by the pipe at the time the defect occurs in the pipe also is determined and provided to the data processing system. The system and methodology further comprise using the data regarding the defect type, the fatigue life accumulation data for the pipe, and the number of cycles experienced by the pipe at the time of the defect to estimate a remaining number of cycles until failure of the pipe.

Abstract: Hybrid frequency/time-domain modeling may be used to compute the synthetic transient response to an eddy-current pulse for use in a high-dynamic-range and efficient inversion method for pulsed-eddy-current pipe inspection tools. In accordance with some embodiments, frequency-domain response signals are computed for a plurality of frequencies and converted, by frequency-to-time-domain transformation, to a first synthetic transient response signal. A time boundary associated with an onset of spurious oscillations in the first synthetic transient response signal is then automatically determined, and a second synthetic transient response signal beginning at the determined time boundary is determined directly with a time-domain numerical technique. A portion of the first synthetic transient response signal ending at the time boundary may be combined with the second synthetic transient response signal.

Abstract: A perforating gun assembly includes a perforating gun body, a casing collar locator, and a direct connect sub coupled to the CCL and the perforating gun body. In an embodiment, the direct connect sub includes a single body including a central axis, a first end, and a second end. The first end is engaged with the CCL, and the second end is engaged with the perforating gun body.

Abstract: A downhole cement plug includes a casing collar locator (CCL) operable to generate signals indicative of casing collars on a downhole casing string of a wellbore system; a controller communicably coupled to the CCL to output a plurality of distinct frequency signals based on the signals from the casing collar locator; and a signal generator communicably coupled to the controller to receive the plurality of distinct frequency signals from the controller and transmit the plurality of distinct frequency signals to a terranean surface through a portion of a wellbore system.

Abstract: Various embodiments include apparatus and methods to utilize signals acquired from a multi-component induction tool operating in a wellbore. The acquired signals can be correlated to apparent conductivity of a formation and mapped to components of an apparent conductivity tensor. For each receiver array operated by the multi-component induction tool, a combination of these components from the acquired signals can be generated. Combinations generated from different receivers of the multi-component induction tool can be mixed together. From such combinations, data, with respect to evaluation of formation around the wellbore, can be generated. Additional apparatus, systems, and methods are disclosed.

Abstract: A corrosion detection system for a pipe may include a corrosion detection tool. The corrosion detection tool may include a transmitter and a receiver. The transmitter and receiver have measurements associated with each and these measurements may be used to determine an impedance. Derived constants match a numerical model that is based on the measurements associated with the transmitter and the nominal thickness of the pipe. The information related to the thickness of a pipe surrounding the corrosion detection is based on the derived constants and the impedance. This thickness of the pipe may be used to determine if a section of a pipe has a defect, such as, corrosion.

Abstract: A methods for the detection of pipe characteristics. The method may comprise disposing a defect detection tool in a wellbore, processing measurements from the defect detection tool in the wellbore to obtain a well log, storing the well log in a database, importing the well log from the database into inversion software, loading a well plan into the inversion software, determining collar locations on at least one concentric pipe in the wellbore utilizing a collar locator algorithm in the inversion software using the well log and well plan, calibrating a forward model in the inversion algorithm utilizing a calibration algorithm in the inversion software, generating an output log utilizing the inversion algorithm in the inversion software on the inversion zone, and determining false metal loss in the output log using the output log.

Abstract: The present invention concerns a downhole cable or control line detection tool. More particularly, but not exclusively, this invention concerns a method and apparatus for the downhole detection of a cable or control line associated with the external wall of a well casing. A downhole tool for the detection of downhole cable or control lines is provided. The downhole tool comprises an eddy current sensor, the eddy current sensor being arranged to be proximate to the internal wall of a well casing. The eddy current sensor is arranged for pulsed operation. The downhole tool further comprises a mechanism for rotating the eddy current sensor, with an axis of rotation parallel with the longitudinal axis of a well casing.

Abstract: The operational position of a moveable device is detected using an electromagnetic induction logging tool. The logging tool generates a baseline log of the moveable device in a non-actuated position, and a response log of the moveable device in an actuated position. The baseline and response logs are then compared in order to determine the operational position of the moveable device.

Abstract: A magnetic imaging tool includes a body including at least two transmitters to transmit signals. The tool further includes an array of sensors coupled to the body to obtain eddy current responses to the signals from downhole tubulars. The array is located axially between two transmitters that produce magnetic fields with opposite orientations.

Abstract: A method and apparatus for seismic sensing is described. The apparatus includes an outer cable coupled to a formation and an outer fiber component proximate to the outer cable. When seismic P- and S-waves propagate from the formation to the outer cable, strain is placed on the outer fiber cable, which may be measured by a distributed acoustic sensing system coupled to the outer fiber cable. An inner cable positioned within the outer cable includes a corresponding inner fiber component. The innerduct between the outer and inner cables is filled with a gas or fluid which allows only P-waves to propagate to the inner cable. Those P-waves induce strain on the inner fiber component, which may be measured by the distributed acoustic sensing system. By measuring the seismic P- and S-waves at the outer fiber component, and the isolated seismic P-wave at the inner fiber component, it is possible to calculate an isolated seismic S-wave measurement. Methods for deploying the seismic sensing apparatus are also described.

Abstract: A corrosion monitoring method includes obtaining electromagnetic (EM) log, data along a casing string. The method also includes processing the EM log data to estimate casing thickness of the casing string as a function of position, where the processing includes correcting, for junction effects in the casing string.

Abstract: A downhole device may include a closed ring of ferromagnetic material mounted on a conductive pipe. The downhole device may also include a first coil spirally wound around the closed ring comprising an electrically conductive flat metallic strip to substantially cover the closed ring.

Abstract: A system and method for inspecting a tube comprising a telemetry module, a centralizing module, an inspection device, a differential amplifier, a sensor array, and a service device. In embodiments, a tube inspection device may comprise a sensor array. The sensor array may further comprise a center receiver coil, a ferri-core, a peripheral receiver, and a transmitter coil. A method for inspection a tube may comprise inserting an inspection device into a tube, energizing a sensory array, inducing an eddy current within the tubing, and measuring voltage with a center receiver coil and a peripheral receiver of the sensor array.

Abstract: An apparatus for supporting a tool in an assembled apparatus. The apparatus includes a support structure, the support structure having a central member and a plurality of support members pivotally mounted on the central member. The support members are movable between a non-deployed position in which the support members extend a minimum distance from the central member and a deployed position in which the support members extend a maximum distance from the central member.

Abstract: A magnetic sensor array is presented for a well apparatus for determining the position of at least one movable component with respect to a fixed component of a downhole tool. The array comprises at least one conductor member having a plurality of contact regions spaced apart at first intervals of at least a first length along a longitudinal axis of said at least one conductor member and a plurality of magnetic sensors, each one of which is operably coupled to one of said plurality of contact regions and actuatable by a magnetic field from a magnetic actuator.

Abstract: Systems, apparatuses, and methods for measuring material thickness of one or more casings using a permeable core are presented. A magnetic field is generated using a permeable core and transmitted through one or more casings. Moreover, one or more receivers measure changes to the magnetic field.

Abstract: The present invention provides a probe apparatus and an associated method for measuring a magnetite deposit thickness, which apparatus and method is independent of the porosity and magnetic permeability of the magnetite deposit. The probe apparatus of this invention is an axial scanning and inside surface-following probe that can accurately and reliably measure the inside diameter of a tube. The probe apparatus of the present invention optionally comprises two modules: the first module is the surface-following module and the second module is a conventional eddy current probe.

Abstract: An inductive, conductivity sensor comprising a transmitting coil, a receiving coil and, surrounding the transmitting coil and the receiving coil, a housing, which has, for immersion in a measured medium, at least one housing section, whose housing wall surrounds the transmitting coil and the receiving coil. The housing wall of the housing section surrounding the transmitting coil and the receiving coil has a multi-ply construction, which comprises at least a first ply of a first material and a second ply of a second material different of the first material.

Abstract: A downhole tool having a first packing element and a second packing element configured to synchronically set to selectively hydraulically isolate a portion of the wellbore. The movement of a pin along a j-slot track on a second sleeve sets the second packer in compression and the movement of a pin along a j-slot track on a first sleeve the first packer in tension after the second packer has been set. The j-slot track on the first sleeve has six different pin positions and the j-slot track on the second sleeve has four different pin positions. The pin positions and direction of travel of the j-slot tracks are adapted to permit the synchronized setting of the two packing elements to hydraulically isolate a portion of the wellbore. The wellbore may then be treated by flowing fluid out of a ported sub positioned between the packing elements.

Abstract: The apparatus employs the remote field eddy-current (RFEC) inspection technique to electromagnetically measure physical parameters of a metallic pipe. RFEC devices inserted into and displaced along a cylindrical pipes may be used to measure the ratio of pipe thickness to electromagnetic skin-depth and thus allow for the non-invasive detection of flaws or metal loss. Typically these RFEC thickness measurements exhibit a so-called double-indication of flaws, an undesired artifact due to a double-peaked geometrical sensitivity function of the device. The method describes a means by which this double indication artifact may be removed by an appropriate processing of RFEC measurements performed by an apparatus specifically designed for this purpose. The invention is particularly well designed for applications in the oilfield industry.

Abstract: A positioning tool for determining the position of the tool in a case downhole. The positioning tool utilizes a detecting unit which includes at least a first magnet and a first sensor in a first plane as well as a second sensor also arranged in the first plane. The first and second sensors are configured to detect changes in a magnetic field generated by the first magnet. The first sensor is arranged at a first distance from the first magnet and the second sensor is arranged at a second distance from the first sensor in the first plane.

Abstract: To realize a wireless communication apparatus with high transceiver coil mounting density, provided is a wireless communication apparatus comprising a plurality of differential coil pairs that respectively transmit and receive differential signals to and from a plurality of external differential coil pairs, through magnetic coupling, wherein one coil in a first differential coil pair among the differential coil pairs is provided at a distance from each of two coils of a second differential coil pair among the differential coil pairs that is less than or equal to a distance between the two coils of the second differential coil pair, and the other coil of the first differential coil pair is provided at a distance from each of the two coils of the second differential coil pair that is greater than the distance between the two coils of the second differential coil pair.

Abstract: A method for magnetizing a portion of a pre-deployed casing string includes deploying an electromagnetic array in a cased wellbore and energizing the array. The array includes a plurality of axially spaced electromagnets and is configured to generate a magnetic field pattern having at least first and second pairs of magnetically opposing poles. Passive ranging measurements of the induced magnetic field may be advantageously utilized, for example, to survey and guide continued drilling of a twin well. The electromagnetic array may also be used in active ranging applications. An array of permanent magnets providing a similar magnetic field pattern may also be used in active ranging applications.

Abstract: A method for transmitting a signal between a wall and a leaf hinged to the wall around an articulation axis includes providing a first signal transmission coil comprising a face side on the wall or on the leaf. A second signal transmission coil comprising a face side is provided on the wall or on the leaf. A carrier voltage is modulated via the signal to be transmitted so as to obtain a modulated carrier voltage. The modulated carrier voltage is applied to the first signal transmission coil so as to generate a secondary voltage modulated by the signal to be transmitted in the second signal transmission coil via an inductive coupling. The first signal transmission coil and the second signal transmission coil are arranged symmetrically with respect to the articulation axis and to face each another on their respective face sides.

Abstract: A method and apparatus for the non-destructive testing of electrically conductive components such as wellbore tubulars, which is suitable for testing the components in situ a wellbore installation. The method comprises the steps of performing a remote field eddy current test phase and at least one of a conventional direct-field eddy current test phase and a partial saturation eddy current test phase. A measurement data set from each of the test phases is obtained and the combined measurement data is processed to evaluate a condition of the test component.

Abstract: An apparatus is provided for sensing anomalies in a long electrically conductive object to be inspected. The object may be a pipeline, or other hollow tube. The apparatus may have a magnetic field generator, and an array of sensors spaced about the field generator. As relative motion in the longitudinal direction occurs between the apparatus and the object to be inspected, the moving magnetic field, or flux, passed from the field generator into the object to be inspected may tend to cause eddy currents to flow in the object. The sensors may be spaced both axially and circumferentially to permit variation in magnetic flux, or eddy current divergence, to be sensed as a function of either or both of axial position relative to the wave front of the magnetic field (or, effectively equivalently any other known datum such as the radial plane of the midpoint of the field generator), and circumferential position about the periphery of the apparatus as measured from an angular datum.

Abstract: The apparatus employs the remote field eddy-current (RFEC) inspection technique to electromagnetically measure physical parameters of a metallic pipe. RFEC devices inserted into and displaced along a cylindrical pipes may be used to measure the ratio of pipe thickness to electromagnetic skin-depth and thus allow for the non-invasive detection of flaws or metal loss. Typically these RFEC thickness measurements exhibit a so-called double-indication of flaws, an undesired artifact due to a double-peaked geometrical sensitivity function of the device. The method describes a means by which this double indication artifact may be removed by an appropriate processing of RFEC measurements performed by an apparatus specifically designed for this purpose. The invention is particularly well designed for applications in the oilfield industry.

Abstract: An insertion type eddy current flaw detection probe capable of more accurately detecting flaws in magnetic tubes is provided. A method for inspecting magnetic tubes for flaws with high accuracy is also provided. A eddy current flaw detection probe contains a cylindrical yoke (1), a plurality of detection coils (5) disposed around the central portion of the cylindrical yoke in the direction of a cylindrical axis thereof, first and second inner excitation coils (6) disposed on both sides of the plurality of detection coils in the direction of the cylindrical axis, and first and second permanent magnets (3, 4) disposed around the yoke on both sides of the first and second excitation coils in the direction of the cylindrical axis so that the direction of magnetizations thereof are parallel to the radial direction of the yoke and magnetic poles on the cylindrical yoke side thereof are different from each other.

Abstract: A non-destructive inspection system that has particular application for inspecting a bore in a valve for defects. The system includes an inspection yoke having a ferromagnetic core, where a first coil is wound around the core in one direction and a second coil is wound around the core in an orthogonal direction so that orthogonal electromagnetic fields can be generated within the bore. A controller provides a current flow through the coils to generate the electromagnetic fields to detect defects in the bore.

Abstract: An inspection assembly for insertion inspection of an elongate hollow member. The inspection assembly includes a probe head including at least one sensor for sensing a characteristic of the elongate hollow member as the probe head is moved internally within the elongate hollow member. The assembly includes a flexible shaft connected to the probe head and transmitting a motive force to the probe head to move the probe head within the elongate hollow member. The flexible shaft encloses at least one wire operatively connected between the probe head and at least one component external to the elongate hollow member for sensory operation of the at least one sensor. The flexible shaft is at least partially corrugated.

Abstract: A method and apparatus in which at least two different test phases are performed on a test object, selected from: conventional eddy current testing, partial saturation eddy current testing, and ultrasonic testing. Measurement data sets are obtained from the at least two different test phases, with each measurement data set comprising measurement data corresponding to a plurality of test positions. The data sets are combined in a data processing means and the combined measurement data is processed to evaluate a damage condition of the test object. In a preferred embodiment, all of conventional eddy current testing, partial saturation eddy current testing, and ultrasonic testing are performed. The apparatus may be provided in two or more sub-assemblies, of which one may be an internal test tool and one may be an external tool. Alternatively, the apparatus may be capable of carrying out all three of the test phases.

Abstract: A magnetizer for a pipeline inspection tool. The magnetizer comprises a ferromagnetic base member, a pair of driving magnets mounted at spatially separate locations on the base member and a flux enhancing magnet mounted on the base member adjacent to one or both of the driving magnets. The directions of magnetization of the pair of driving magnets extend in opposite senses to each other, towards and away from the base member respectively to create a magnetic circuit that includes a flux path between the driving magnets which passes through the base member. The flux enhancing magnet has a direction of magnetization substantially aligned with the direction of magnetic flux on the flux path, the flux enhancing magnet being magnetically coupled to the adjacent driving magnets to drive flux around the magnetic circuit and thereby enhance the magnitude of a magnetic field exhibited by the magnetic circuit outside the magnetizer.

Abstract: An apparatus comprising a probe having an elongated probe casing includes a magnetometer and a permanent magnet having a north-south magnetic axis disposed in an orientation relative to a longitudinal axis of a drill string or pipe casing when the probe is inserted into the drill string or the pipe casing. The permanent magnet is disposed in a non-vertical plane that does not contain the longitudinal axis to induce a magnetic field in the plane from the north of the magnetic axis to the south of the magnetic axis along a portion of a circumference of the drill string or the pipe casing. The magnetometer is to detect magnetization of the drill string or the pipe casing independently of movement of the permanent magnet. Additional apparatus and methods of analysis using the apparatus are disclosed.

Abstract: An eddy current probe for inspecting steam generator tubing, that has radially outwardly biased rollers that function to center the probe within the tubing and reduce friction as the probe moves along the interior of the steam generator heat exchanger tube walls. The rollers may include a braking system which controls the drag on the rollers and thus the speed of the probe along the tubing. The direction of travel of the rollers is remotely adjustable to control the inspection pattern and the force of the rollers against the interior surface of the tubing can be remotely controlled.

Abstract: A device and method for inspecting an inspection object of in the vicinity of a further object, both of electrically conductive material, the device comprising a transmitter/receiver arrangement for generating an electromagnetic field in the inspection object, and for measuring a signal indicative of a transient eddy current which is generated in the inspection object by the electromagnetic field, wherein the device further comprises a magnetic shield means, providing at least a partial magnetic shield for the transmitter/receiver arrangement in a direction other than a measurement direction; use of the device from inside an annulus between an inner and an outer tubular, and a method of operating a hydrocarbon well having a well completion, and inspecting the well completion from inside an annulus.

Abstract: A pipeline pig signal made according to this invention houses one or more shielded magnetometer sensors and a microcontroller with adaptive thresholding detection means for reducing the likelihood of false alarms. The adaptive thresholding detection means removes outlier data from the magnetic flux data stream and then passes the outlier-free data stream through four low pass filters. A smoothed magnitude of the data stream is compared to detection limits and, if a passage event has occurred, a recent detection is indicated, a counter of a display unit is incremented, a time of passage is recorded, and both statistics are displayed on the display unit. Because a single object may produce multiple magnetic fields, the detector may be locked-out for a predetermined period of time after the passage event to prevent a second detection of the same object as it passes the detection device.

Abstract: A segmented magnetostrictive patch array transducer capable of generating a high frequency shear wave in a structure such as a rod or a pipe, a structural fault diagnosing apparatus including the segmented magnetostrictive patch array transducer, and a method of operating the segmented magnetostrictive patch array transducer are shown. The segmented magnetostrictive patch array transducer includes a plurality of magnetostrictive patches attached along a circumference of a rod member; a plurality of insulators that are disposed on the magnetostrictive patches; a plurality of meander coils, each of the meander coils comprising a plurality of coil lines extending along the circumference direction of the rod member on each of the insulators, wherein a current flows through adjacent coil lines in opposite directions to one another; and a plurality of magnets that respectively form a magnetic field along the circumferential direction of the rod member on the magnetostrictive patches.

Abstract: A detection apparatus for an eddy current in a heat generating tube using a permeability measurement method, and a method using the apparatus are provided. In the detection apparatus, a bobbin type probe acquires detection information with respect to a magnetic flux change by a magnetic phase occurring in the heat generating tube using a coil which is wound in an axis direction of at least one yoke located in a perpendicular direction with a bobbin of the bobbin type probe, and a material having a corresponding magnetic phase and a circumferential defect, which is difficult to be detected by the bobbin type probe, are detected based on the detection information.

Abstract: The invention discloses a method for electromagnetically measuring physical parameters of a pipe that includes measuring a pipe inner diameter ID and a pipe ratio of magnetic permeability to electrical conductivity ?2/?2 by means of a measuring arrangement 1 comprising a transmitter coil 2 and a receiver coil 3, both coils being coaxial to and longitudinally spaced from each other, the measuring arrangement being adapted to be positioned into the pipe CS and displaced through the pipe.

Abstract: An operational monitoring system for use in communications, and a method thereof, for operational, systems or integrity management of pipeline infrastructures which operates by broadcasting wireless signals through gas distribution networks and analyzing the traversed signals to assess the operational, systems or integrity of the natural gas pipelines. The operational monitoring system includes a transmitter located at a first location arranged to transmit a wireless signal through natural gas contained within a pipeline infrastructure; a receiver located at a second location structured to receive the wireless signal transmitted through the natural gas contained within the pipeline infrastructure; and a device to analyze the received wireless signal indications of operational changes in the natural gas pipeline infrastructure.

Abstract: A method for determining electrical condition of a wired drill pipe includes inducing an electromagnetic field in at least one joint of wired drill pipe. Voltages induced by electrical current flowing in at least one electrical conductor in the at least one wired drill pipe joint are detected. The electrical current is induced by the induced electromagnetic field. The electrical condition is determined from the detected voltages.

Abstract: Various embodiments comprise a probe for analysis of a collection of rods or tubes, including an elongated casing which bears, at a first end, at least one first magnetometer and, at a position sufficiently remote from the magnetometer, a permanent magnet, the north-south axis of which may be perpendicular to the axis of the rods. Additional apparatus, systems, and methods are disclosed.