Patent ID: 7598734
Filing Date: 2009-10-06
Classification: G01D

Abstract:
1. 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 shield member disposed around said detection coil; (a) said shield member is a tubular member having an axial region, which is formed in an electrically discontinuous manner with respect to a circumferential direction of said tubular member; (b) said shield member is a tubular member having a first shield portion for surrounding an axial region of said detection coil, and a second shield portion for surrounding another axial region of said detection coil, and said second shield portion is made of a material having a different electric conductivity or magnetic permeability from said first shield portion; (c) said shield member is a tubular member having a first inner surface for surrounding an axial region of said detection coil, and a second inner surface for surrounding another axial region of said detection coil, and a distance between said second inner surface and said detection coil is smaller than the distance between said first inner surface and said detection coil.