embodiments a sensor with microcoils may allow the instrumented antifriction bearing to deliver reliable information even when magnetic fields of high intensity are present the encoder may be made of an electrically conducting and magnetic metal material such as steel or electrically conducting and nonmagnetic material such as aluminum or copper reception microcoils 20 may operate in pairs to deliver a differential signal the reception microcoils 20 of a pair may be angularly offset by an angle represented by u03b2 an angular pitch of the windows is represented by u03c6 for the signal to be out of phase one of these angles may not be a multiple of the other this therefore gives u03b2 u2260 a u03c6 where a is any integer the angle u03b2 usually being greater than u03c6 for example this could be u03b2 a 0 5 u03c6 or u03b2 a 0 25 u03c6 when an encoder passes in rotation before the sensor the discontinuities of material of the operational portion 14 may cause periodic variations of the metal mass that is opposite the reception microcoils 20 if there is metal material before each of the coils of a pair of reception coils the phase difference between the two differential coils may be zero if there is metal material before at least one of the two reception coils forming a pair and the metal material is distributed differently before each coil the losses due to the eddy currents in the metal material may generate a phase difference of the currents this phase difference may then be processed and extracted adequately by the processing circuit 18 in order to obtain desired information such as angular.