Detection of corrosion and other defects in piping is needed to prevent catastrophic pipeline failure. Sensors, systems and methods are provided to enable detection of such defects. These apparatus and methods are configured to characterize pipe protected by insulation and conductive weather protection. The sensors may utilize inductive and/or solid state sensing element arrays operated in a magnetic field generated in part by a drive winding of the sensor. Multiple excitation frequencies are used to generate the magnetic field and record corresponding sensing element responses. Relatively high excitation frequencies may be used to estimate the properties of the weather protection and sensor lift-off while lower frequencies may be used to detect internal and external pipe damage. Linear arrays may be moved to generate damage images of the pipe providing size and location information for defects. Two dimensional sensor arrays may be used to provide imaging without moving the sensor.

A fluxgate device that includes a first magnetic core and a second magnetic core. The first magnetic core has a first magnetized direction that deviates from a first sense direction by more than 0 degree and less than 90 degrees. The second magnetic core is arranged orthogonally to the first magnetic core. The second magnetic core has a second magnetized direction that deviates from a second sense direction by more than 0 degree and less than 90 degrees.

A fluxgate device that includes a first magnetic core and a second magnetic core. The first magnetic core has a first magnetized direction that deviates from a first sense direction by more than 0 degree and less than 90 degrees. The second magnetic core is arranged orthogonally to the first magnetic core. The second magnetic core has a second magnetized direction that deviates from a second sense direction by more than 0 degree and less than 90 degrees.

A magnetic field calibration device is used to calibrate a magnetism measurement device having a plurality of magnetic sensors and includes a first holder having a first holding surface, a second holder having a second holding surface having a fixed relative positional relation with the first holding surface, and magnetism generating parts fixed to the first holding surface and the second holding surface. Thus, calibration can be completed with a single operation by assigning the first and second holding surfaces of the magnetic field calibration device respectively to the first and second measurement surfaces of the magnetism measurement device. In addition, since the relative positional relation between the first and second holding surfaces is fixed, measurement results obtained from the individual measurement surfaces match each other.

The invention relates to a magnetic field measurement device, including a detector (4) configured to measure the amplitude of an output signal at a harmonic of an oscillation frequency of an excitation source, said amplitude being proportional to the magnetic field (B) to be measured, characterised in that it comprises an excitation circuit configured to associate with a principal excitation source (B.sub.1cosωt) oscillating at a principal oscillation frequency at least one secondary excitation source (B.sub.2cos(ω/3t+Φ.sub.2)) oscillating at a secondary oscillation frequency that is a fraction of the principal oscillation frequency, said fraction being odd if said harmonic is odd, and even if said harmonic is even.

The invention relates to a magnetic field measurement device, including a detector (4) configured to measure the amplitude of an output signal at a harmonic of an oscillation frequency of an excitation source, said amplitude being proportional to the magnetic field (B) to be measured, characterised in that it comprises an excitation circuit configured to associate with a principal excitation source (B.sub.1cosωt) oscillating at a principal oscillation frequency at least one secondary excitation source (B.sub.2cos(ω/3t+Φ.sub.2)) oscillating at a secondary oscillation frequency that is a fraction of the principal oscillation frequency, said fraction being odd if said harmonic is odd, and even if said harmonic is even.

Systems and methods are presented for cancelling noise from sensed magnetostriction-based strain measurements. A drive signal corresponds to a drive coil, and a sensed signal corresponds to a sensed coil. The drive signal is used to at least partially eliminate noise similar to the drive signal from the sensed signal to generate an output signal.

A magnetic hotspot detector is capable of locating magnetic hotspots in tubulars, such as tubulars for use downhole. A sensor array can include multiple sets of differential fluxgate magnetometers, each set comprising two non-differential fluxgate magnetometers arranged across the diameter of a tubular to be measured. As the tubular passes through the sensor array, fluctuations in magnetic field due to the movement of the tubular through the sensor array are measured to provide indication of the location of magnetic hotspots. To locate hotspots, a tubular can be passed through the sensor array or the sensor array can pass over the tubular.

A magnetic hotspot detector is capable of locating magnetic hotspots in tubulars, such as tubulars for use downhole. A sensor array can include multiple sets of differential fluxgate magnetometers, each set comprising two non-differential fluxgate magnetometers arranged across the diameter of a tubular to be measured. As the tubular passes through the sensor array, fluctuations in magnetic field due to the movement of the tubular through the sensor array are measured to provide indication of the location of magnetic hotspots. To locate hotspots, a tubular can be passed through the sensor array or the sensor array can pass over the tubular.

An apparatus and a method for refining a geographical location based on dynamic characteristics of a helmet are disclosed. A piece of angular velocity information is sensed through a gyroscope and then compared with a piece of basic angular velocity information to generate a piece of dynamic information of the helmet body. The piece of dynamic information, the piece of location information, and the piece of magnetic flux information are marked on an electronic map to generate a piece of refined geographical location information which is then sent to an output unit to be outputted. Thus, a higher resolution of the current geographical location is obtained.