Position sensor with a shield member for improving linearity of impedance of the detection coil

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;
• wherein said shield member has at least one of the following features (a) to (c) for improving linearity of impedance of 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.