Magnetic detection device for detecting the absolute position of a rotating input shaft, comprising: * a main rotor comprising a main magnet integral with said input shaft travelling n times through 360°, wherein n is at 1 and a driving member for motion transformation, * at least one first magnetic field-sensitive sensor delivering, over a magnetic angle of 360 degrees, a signal proportional to the direction of the magnetic field generated by the main magnet in order to deduce an absolute position measurement of the input shaft, * a secondary magnet having 2 magnetic poles, * at least one second magnetic field-sensitive sensor delivering, over a magnetic angle of 360 degrees, a signal proportional to the direction of the magnetic field generated by the secondary magnet and capable of deducing therefrom an absolute position measurement of the secondary magnet, - wherein the second sensor and the secondary magnet form a position sensor of a precision epsilon, expressed in per cent, - wherein the main magnet is multipolar and has P pairs of poles, with P being greater than 1, characterised: * in that the first and second magnetic field-sensitive sensors (6, 7) are arranged so as to deliver a signal over a magnetic angle of 360 degrees * in that the secondary magnet, which travels through nearly 360 degrees under the effect of the rotation of the input shaft travelling n times through 360° via the motion transformation taking place in a section of the space included in the section containing the main magnet, is substantially positioned within the height H defined by the upper and lower planes of the main rotor, * in that P is less than the integer part of 360 / T, with T > epsilon 50 360. n + Hyst where Hyst is the amplitude of the hysteresis of the detection device, expressed in degrees and with reference to the input shaft and in that the main magnet is contained in the interior volume of the driving member. * a main rotor comprising a main magnet integral with said input shaft travelling n times through 360°, wherein n is at 1 and a driving member for motion transformation, * at least one first magnetic field-sensitive sensor delivering, over a magnetic angle of 360 degrees, a signal proportional to the direction of the magnetic field generated by the main magnet in order to deduce an absolute position measurement of the input shaft, * a secondary magnet having 2 magnetic poles, * at least one second magnetic field-sensitive sensor delivering, over a magnetic angle of 360 degrees, a signal proportional to the direction of the magnetic field generated by the secondary magnet and capable of deducing therefrom an absolute position measurement of the secondary magnet, - wherein the second sensor and the secondary magnet form a position sensor of a precision epsilon, expressed in per cent, - wherein the main magnet is multipolar and has P pairs of poles, with P being greater than 1, - wherein the second sensor and the secondary magnet form a position sensor of a precision epsilon, expressed in per cent, - wherein the main magnet is multipolar and has P pairs of poles, with P being greater than 1, * in that the first and second magnetic field-sensitive sensors (6, 7) are arranged so as to deliver a signal over a magnetic angle of 360 degrees * in that the secondary magnet, which travels through nearly 360 degrees under the effect of the rotation of the input shaft travelling n times through 360° via the motion transformation taking place in a section of the space included in the section containing the main magnet, is substantially positioned within the height H defined by the upper and lower planes of the main rotor, * in that P is less than the integer part of 360 / T, with T > epsilon 50 360. n + Hyst where Hyst is the amplitude of the hysteresis of the detection device, expressed in degrees and with reference to the input shaft and in that the main magnet is contained in the interior volume of the driving member. where Hyst is the amplitude of the hysteresis of the detection device, expressed in degrees and with reference to the input shaft and in that the main magnet is contained in the interior volume of the driving member.