An exemplary method of indicating a condition of grout within a post-tensioned tendon involves positioning a magnet and a metallic sensing plate in close proximity to an outer surface of the post-tensioned tendon; rotating the magnet and the metallic sensing plate around the outer surface of the post-tensioned tendon; measuring an amount of magnetic forces applied to the magnet during rotation of the magnet around the post-tensioned tendon; measuring an impedance between the metallic sensing plate and metallic strands within the post-tensioned tendon during rotation of the metallic sensing plate around the post-tensioned tendon; and generating an image of a cross-section of the post-tensioned tendon indicating one or more grout conditions in spatial proximity to the metallic strands within the post-tensioned tendon based on measurement data using the magnet and the metallic sensing plate.

A system and method for performing synchronization of a magnetic field transmitter and receiver to resolve received signal phase ambiguity based upon the phases of the magnetic fields. Three orthogonal field frequencies are selected. A Fourier transform extracts the sine and cosine of the received signal, which provides the received signal phases and results in a complex signal matrix (“Sigmat”). A search is made for a phase rotation of the frequencies to achieve convergence of the Sigmat at a point it is real-valued; the search may be limited by aligning the Sigmat such that the major element becomes real-valued and rotating the other two frequencies. The correct phase is the one in which the Sigmat has a positive determinant and minimizes any remaining imaginary portion. A transmitter and receiver may be calibrated to account for any analog phase shift. Distortion of the magnetic field may also be detected and corrected.

An exemplary method of indicating a condition of grout within a post-tensioned tendon involves positioning a magnet and a metallic sensing plate in close proximity to an outer surface of the post-tensioned tendon; rotating the magnet and the metallic sensing plate around the outer surface of the post-tensioned tendon; measuring an amount of magnetic forces applied to the magnet during rotation of the magnet around the post-tensioned tendon; measuring an impedance between the metallic sensing plate and metallic strands within the post-tensioned tendon during rotation of the metallic sensing plate around the post-tensioned tendon; and generating an image of a cross-section of the post-tensioned tendon indicating one or more grout conditions in spatial proximity to the metallic strands within the post-tensioned tendon based on measurement data using the magnet and the metallic sensing plate.

A micro-electro-mechanical system (MEMS) magnetometer is provided for measuring magnetic field components along three orthogonal axes. The MEMS magnetometer includes a top cap wafer, a bottom cap wafer and a MEMS wafer having opposed top and bottom sides bonded respectively to the top and bottom cap wafers. The MEMS wafer includes a frame structure and current-carrying first, second and third magnetic field transducers. The top cap, bottom cap and MEMS wafer are electrically conductive and stacked along the third axis. The top cap wafer, bottom cap wafer and frame structure together form one or more cavities enclosing the magnetic field transducers. The MEMS magnetometer further includes first, second and third electrode assemblies, the first and second electrode assemblies being formed in the top and/or bottom cap wafers. Each electrode assembly is configured to sense an output of a respective magnetic field transducer induced by a respective magnetic field component.

A magnetometer includes a vapor cell having at least one wall, a chamber defined by the at least one wall, and alkali metal atoms disposed in the chamber to produce an alkali metal vapor in the chamber, wherein the at least one wall includes an oxide-containing interior surface; and an anti-relaxation coating disposed on the oxide-containing interior surface of the at least one wall of the vapor cell, wherein the anti-relaxation coating is a reaction product of the oxide-containing interior surface of the at least one wall with at least one mono- or dichlorosilane compound.

A magnetometer includes a vapor cell having at least one wall, a chamber defined by the at least one wall, and alkali metal atoms disposed in the chamber to produce an alkali metal vapor in the chamber, wherein the at least one wall includes an oxide-containing interior surface; and an anti-relaxation coating disposed on the oxide-containing interior surface of the at least one wall of the vapor cell, wherein the anti-relaxation coating is a reaction product of the oxide-containing interior surface of the at least one wall with at least one mono- or dichlorosilane compound.

A magnetic field detection device includes a magnetic field detection element, a modulation coil, and a demodulator. The magnetic field detection element has a sensitivity axis in a first direction. The modulation coil is configured to apply, to the magnetic field detection element, an alternating current magnetic field having a first frequency and a component in a second direction, the second direction being orthogonal to the first direction. The demodulator is configured to demodulate an output signal having the first frequency and outputted from the magnetic field detection element, and detect, on a basis of an amplitude of the output signal, an intensity of a measurement magnetic field to be received by the magnetic field detection element.

A method may include measuring an electrical parameter of an electromagnetic load having a moving mass during the absence of a driving signal actively driving the electromagnetic load, measuring a mechanical parameter of mechanical motion of a host device comprising the electromagnetic load, correlating a relationship between the mechanical parameter and the electrical parameter, and calibrating the electromagnetic load across a plurality of mechanical motion conditions based on the relationship.

A method may include measuring an electrical parameter of an electromagnetic load having a moving mass during the absence of a driving signal actively driving the electromagnetic load, measuring a mechanical parameter of mechanical motion of a host device comprising the electromagnetic load, correlating a relationship between the mechanical parameter and the electrical parameter, and calibrating the electromagnetic load across a plurality of mechanical motion conditions based on the relationship.

Disclosed is a magnetizing pulse detector that detects magnetizing pulses produced by a magnetizing coil; the magnetizing pulse detector comprising: a measuring coil configured to generate a measuring pulse in response to a magnetizing pulse produced by the magnetizing coil; a measuring pulse detection circuit configured to generate a detection signal based on the measuring pulse generated by the measuring coil; and a duration extension circuit configured to generate an extended detection signal based on the detection signal generated by the measuring pulse detection circuit.