Patent ID: 7679361

Claim:
A position sensor comprising: a tubular detection coil; a magnetic core movable in said detection coil; a drive circuit configured to provide a constant alternating voltage or a constant alternating current to said detection coil; a signal processing circuit configured to convert a change in impedance of said detection coil caused by a displacement of said magnetic core in said detection coil into an electric signal; and a guide comprising a guide portion connected to said magnetic core and a support portion configured to slidably support said guide portion, wherein said guide is formed such that said magnetic core is displaced in said detection coil without contacting an inner surface of said detection coil by a sliding movement of said guide portion relative to said support portion, wherein said guide portion has at least one guide bar extending generally parallel to said magnetic core, wherein said support portion has an opening, in which said magnetic core is inserted, at an end of said detection coil, and at least one guide opening, in which said at least one guide bar is inserted, at the periphery of said opening, and wherein said at least one guide bar inserted in said at least one guide opening is movable in an axial direction of said detection coil at the outside of said detection coil.