The present disclosure relates to electromagnetic marker devices for locating hidden or buried objects. One embodiment includes an antenna having a plurality of conductive windings enclosed in a housing made of a low dielectric constant material and an electronic circuit including a circuit board having circuit elements disposed thereon and electrically coupled to the conductive windings through a connector. The circuit elements receive an input signal having a first frequency from an above-ground transmitter, convert the input signal to a power supply to power up the electronic circuit, generate, in response to the input signal, an output signal having a second frequency different from the first frequency, and provide the output signal, via the antenna element, to an above-ground receiver.

An apparatus and a method provide an output signal indicative of a speed of rotation and/or a direction of movement of a ferromagnetic object. The sensor includes at least one magnetic field sensing element configured to generate a magnetic field signal in response to a magnetic field associated with an object. The sensor includes a detector configured to generate a detector signal having edges occurring in response to a comparison of the magnetic field signal and the threshold signal. The sensor includes an output circuit configured to generate an output signal having a first format when a characteristic of the magnetic field signal is within a first range and having a second format different than the first format when the characteristic of the magnetic field signal is within a second range, different than the first range.

A method for magnetic ranging includes switching an electromagnet deployed in a target wellbore between at least first and second states and acquiring a plurality of magnetic field measurements at a magnetic field sensor deployed on a drill string in a drilling wellbore while the electromagnet is switching. The magnetic field measurements may be sorted into at least first and second sets corresponding to the first and second states of the electromagnet. The first and second sets of magnetic field measurements are then processed to compute at least one of a distance and a direction from the drilling well to the target. The electromagnet may be automatically switched back and forth between the first and second states independently from the acquiring and sorting of the magnetic field measurements.

An improved detector device for locating studs and other objects behind a substrate (such as a wall) uses one or more light emitting diodes (LEDs) in combination with a photochromic compound to mark the locations on the substrate behind which objects are located.

A containment area can be defined by a single cable carrying an asymmetric electromagnetic signal that generates a magnetic field comprising an asymmetric waveform. A single inductor circuit configured to detect a single axis of the magnetic field can detect the asymmetric waveform and determine which direction the inductor is traveling relative to the cable. A human-propelled cart can have a wheel that includes the single inductor circuit and detect whether the cart is being pushed from inside-to-outside the containment area (which may reflect the cart is being stolen or improperly used) or from outside-to-inside (which may reflect the cart is being returned). The cart can include an anti-theft system (e.g., a locking or braking wheel), which can be triggered if the cart is being moved from inside to outside the containment area. The single cable, single inductor system can be less expensive and more efficient than multi-cable, multi-inductor systems.

A sensor comprises conductive elements arranged and connected for proximity sensing. The conductive elements are formed of an ionically conductive polymer. The sensor may also include conductive elements arranged and connected for touch sensing. The conductive elements may be connected to an alternating-current (AC) source. Another sensor comprises one or more conductive elements arranged and connected for touch sensing by detecting resistivity changes in the one or more conductive elements. A flexible and transparent sensor is also provided, which comprises a layer of a piezoelectric polymer and conductive elements in contact with the layer for transmitting an electric signal generated by compression of the layer. Methods and processes for using such sensors are also provided.

A proximity sensor comprising: a loop comprising an outer surface and an inner surface, at least a portion of the inner surface being a reflective surface; a light emitter positioned to emit light onto the reflective surface; a light detector positioned to preferentially receive light emitted from the light emitter and reflected from the reflective surface; and a processor that is configured, responsive to a set of instructions stored in a memory, to determine a degree of proximity of an object to the inner surface of the loop responsive to a reduction in an intensity of light emitted from the light emitter that is received by the light detector.

A magnetometer-based metal detection device and methods of use are described. The device includes a proximal portion, a central body and a distal portion, and at least one magnetometer positioned within or on the distal portion. The at least one magnetometer includes at least one sensor capable of sensing a magnetic field in three orthogonal axes. Also described is a method of calibrating the device to achieve rotational invariance, and a method of determining a directionality or directional line along which a target metal object lies.

A precise line locator is presented that provides precise line location. The locator includes a housing; a wand attached to the housing, the wand including an array of low frequency antennas arranged along the wand, the array of low frequency antennas defining an electromagnetic locate axis of the line locator system; a real-time kinematic (RTK) Global Navigation Satellite (GNSS) antenna attached to the housing; a user interface positioned in the housing; and a processing circuit coupled to the array of low frequency antennas, the RTK GNSS antenna, and the user interface, wherein the underground line locator determines locate data of the underground line based on signals from the array of low frequency antennas and determines a precise position of the underground line locator from the RTK GNSS antenna.

The present disclosure relates to a method for advancedly detecting a water-bearing hazard body in real-time based on vector resistivities. The method includes: acquiring potential differences of receiving dipoles on a shield machine in real-time based on a pre-constructed detection environment, wherein the receiving dipoles include first receiving dipoles and a second receiving dipole; converting to resistivities by using a formula for calculating resistivities in a steady current field according to relative positional relationships between the receiving dipoles and power supply dipoles and the potential differences of the receiving dipoles to obtain the apparent resistivities of the receiving dipoles; drawing curves of the apparent resistivities of the receiving dipoles by taking positions of the power supply dipoles as an abscissa axis and the apparent resistivities as an ordinate axis; analyzing the changing curves of the apparent resistivities and determining a detection result of an abnormal body. According to this method, in the process of a continuous underground tunneling of the shield machine, the conditions of the water-bearing hazard body in front of the tunneling is detected in real-time by means of continuously receiving electric signals by the receiving dipoles and drawing the curves of the apparent resistivities of the receiving dipoles, thereby improving the real-time performance of the advanced prediction results.