A calibration procedure for calibrations of triaxial magnetometers is presented. The procedure uses a triaxial Helmholtz coil system and an Overhauser scalar magnetometer and is performed in the Earth's field range. The triaxial coils are firstly calibrated with the Overhauser magnetometer and subsequently a triaxial magnetometer calibration is performed. As opposed to other calibration approaches, neither Earth's field nulling system nor movements of the magnetometer are needed. A real calibration test was carried out -the extended calibration uncertainty was better than 430 ppm in sensitivity and 0.06 degrees in orthogonality.

A calibration of the well-defined Braunbek coil system was carried out using the scalar method. The whole measuring setup was designed to minimize the uncertainty of the scalar calibration procedure. The measurement time as well as the sampling ratio were adjusted to reduce the influence of the ambient magnetic field variation. We calibrated the coil sensitivity with the uncertainty of 30 ppm and orthogonality with the uncertainty <0.01°. The results were compared with a different technique.

Navigation, position tracking, search for unexploded ammunition, and geophysical prospection of magnetic or conducting ore are key applications where very small magnetic field signatures and field increments should be detected in the presence of the Earth's magnetic field, typically 50,000 nT. The industry calls for a new generation of portable vectorial magnetic sensors with a precision better than 0.1 nT. This error requirement includes not only sensor noise but also linearity, cross-field error, hysteresis, and perming and also temperature drift of the sensitivity and mainly the offset drift. For application on moving platform, the sensors should also have fast response. We will show that these requirements can be met only by fluxgate sensors. On the other hand, mass market requires cheap, low-power, and small magnetic sensors for portable gadgets; the typical application is compass in mobile phone, with precision of several degrees, corresponding to a 100-nT precision. For these applications, anisotropic magnetoresistance (AMR) sensor is dominant, while integrated fluxgates may penetrate the high-end market.

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A magnetic distance sensor working at very low frequency has been developed to measure distances up to 1 m. The principle is similar to that of the 3-D magnetic tracker, but the system is optimized to minimize the error in distance for static measurements. The system is not affected by conductive objects. The uncertainty caused by noise and interference is below 2 mm, even in a noisy environment. The measurement time of 3 minutes can be decreased to 1 minute, depending on the amplitude of the interferences and the required accuracy. After applying corrections, systematic error of 5 mm was achieved by using a calibration model. The system is scalable up to 20 m range.

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This paper presents a new long-range full 3D magnetic tracking system for horizontal directional drilling (HDD), and describes its performance. The system is able to determine the full 3D mutual position of the receiver with respect to the transmitter. The system presented here belongs to the category of hybrid trackers using an active magnetic ranger, an optical gyro and three micro-machined inclinometers. The gyro is used for dead-reckoning navigation over long distances (up to 2 km), and the magnetic tracking system, consisting of a coil magnetic transmitter and a magnetometer receiver, is used when two drill heads are approaching each other beneath the surface at the assumed meeting point. The functionality of the system was verified for the maximum range of 17m with 1,2m RMS accuracy, and with 0,34m RMS accuracy for the range below 10m. Index Terms-magnetic tracking, magnetic sensors1530-437X (c)

The eect of demagnetizing factor and manufacturing procedure on noise of the uxgate probes, manufactured from metallic glasses, is presented. The uxgate probes were either tape-wound, or at, wet-etched ringcore and race-track geometries. When combining low demagnetizing factor and high enough cross-section of the probe, a minimum in the noise dependence can be found. For 50 mm ringcores, in such minimum the noise value as low as 7 pTRMS in 0.1-10 Hz frequency band was achieved, which is very low for an as-cast tape, and has not been reported before.