Patent ID: 8159213

Claim:
A non-contact measurement method for a relative displacement or relative positioning of a first object relative to a second object, in which: at least one transmitting coil, placed on the first object, is excited by an alternating excitation signal, at least two alternating electronic output signals, generated by mutual inductance in at least two receiving coils, are detected; said at least two receiving coils being placed on said second object and in a magnetic field created by said at least one transmitting coil, the relative displacement of the first object is determined relative to the second object using said at least two alternating electric output signals generated on said at least two receiving coils, an axial displacement is determined by measuring a continuous axial voltage Va that is proportional to a monotone function of mutual inductance M between one of said at least one transmitting coil and one of said at least two receiving coils, said at least two receiving coils generate, respectively, an alternating voltage va that is proportional to mutual inductance Ma between a first of said at least two receiving coils and one of said at least one transmitting coil, and an alternating voltage vb that is proportional to the mutual inductance Mb between a second of said at least two receiving coils and one of said at least one transmitting coil, a radial displacement is determined by measuring a continuous radial voltage Vr proportional to the relation (Ma−Mb)·f(Ma+Mb); where (Ma−Mb) is the difference between mutual inductances Ma and Mb, where f(Ma+Mb) is a monotone function of the sum (Ma+Mb) of mutual inductances Ma and Mb; where Ma is the mutual inductance between one of said at least one transmitting coil and a first of said at least two receiving coils, where Mb is the mutual inductance between one of said at least one transmitting coil and a second of said at least two receiving coils.