An inductive detector for measuring the position of a first body relative to a second body along a measurement path comprises: a first body which comprises a substantially planar surface and a passive electromagnetic target; a second body which comprises a substantially planar surface facing the planar surface of the first body and an arrangement of laminar windings; said first and second body being configured such that the electromagnetic influence of the first body on the second body varies according to the position of the first body relative to the second body along the measurement path; wherein said passive electro-magnetic target comprises a first portion incorporating said planar surface and a second portion with a lower thickness than said first portion; whereby the second portion incorporates an insulating aperture.