Patent ID: 7919962

Claim:
A magnetic field measuring apparatus, comprising: a magnetic field sensor; a helical path formed over a cylindrical surface of a magnetic core including magnets, the magnetic core having an axis, the magnetic field sensor being capable of measuring a magnetic field along the helical path; a first motor that moves the magnetic field sensor relative to the cylindrical surface; a second motor that rotates the magnetic core about the axis; at least one rail disposed parallel to the axis, the magnetic field sensor being guided by the rail to move in an axial direction when actuated by the first motor, wherein the combination of the second motor rotating the magnetic core and the first motor axially moving the magnetic field sensor moves the magnetic field sensor such that the magnetic field sensor measures the magnetic field along the helical path relative to the cylindrical surface; a first encoder that generates a first value, a rotational angle of the magnetic core being determined based on the first value; a second encoder that generates a second value, an axial position of the magnetic field sensor being determined based on the second value; and a processor that sets a coordinate corresponding to an output of the magnetic field sensor based on the first and second values.