A vector sensor is a sensor that enables measurement of the components of a magnetic field to be measured in a frame of reference with two or three dimensions. Here, in a frame of reference with two dimensions, these components are denoted cX and cY. In a frame of reference with three dimensions, these components are denoted cX, cY and cZ. A vector sensor thus enables measurement of the direction, and preferably also of the amplitude, of the magnetic field. The components cX, cY and cZ correspond to the orthogonal projection of the magnetic field to be measured onto the axes X, Y and Z, respectively, of the frame of reference.
Known magnetic field vector sensors include:    a fixed substrate extending essentially parallel to a plane called the “substrate plane”,    a support mobile relative to the substrate rotatable about at least a vertical rotation axis Z perpendicular to the substrate plane,    a magnetic field source having a magnetic moment in a direction that is not perpendicular to the substrate plane, this source being fixed to the mobile support with no degree of freedom so as to exert a mechanical torque on the support about the vertical rotation axis in the presence of a magnetic field to be measured that is not colinear with the direction of this magnetic moment,    at least one transducer adapted to convert the torque exerted on the mobile support about the rotation axis into an electrical signal representative of the amplitude of a component of the magnetic field to be measured along a measurement axis contained in the substrate plane.
When the magnetic field source is immersed in the magnetic field to be measured, a torque Γ appears that is a function of the magnetic moment of the source, the amplitude of the magnetic field to be measured and the angle between the magnetic moment of the source and the direction of the magnetic field to be measured. This torque Γ tends to cause the mobile support to turn so that the direction of the magnetic moment of the source is aligned with the direction of the magnetic field to be measured. A torque is therefore exerted on the mobile support. This torque, or a magnitude representative of this torque, such as an angular displacement, is measured by the transducers.
However, to determine unambiguously the components cX and cY of the magnetic field to be measured contained in the substrate plane of the sensor, at least two magnetic field sources are necessarily required the magnetic moments of which are aligned in two different directions. Consequently, the known sensors include at least one first mobile support and one second mobile support each carrying a respective one of these magnetic field sources.
The presence of a plurality of mobile supports and a plurality of magnetic field sources gives rise to the following problems in particular:
it increases the overall size of the sensor,
it can cause measurement errors from one sensor to another because it is difficult to position the magnetic field sources in each sensor and to orient them precisely with respect to each other in exactly the same manner, and
magnetic coupling may exist between the different magnetic field sources, which introduces a skew into the measurement.
The prior art also includes US2011/0140693A1 and the paper by Dirk Ettelt et al, “A novel Microfabricated High Precision Vector Magnetometer”, 2011 IEEE Sensors Proceedings: Limerick, Ireland, 28-31 Oct. 2011, pages 2010-2013.