Clinometer for determining the orientation of a body driven or to be driven into the earth

Claim 1

A clinometer for determining the direction of a bore hole and particularly any deviation of that direction from the vertical, comprising: a support means defining a longitudinal axis and provided for disposition in the bore so that the axis assumes an orientation corresponding to said direction; a pendulum pivotally supported by said support means for pivotable movement about a pendulum axis extending transversely to and intersecting said longitudinal axis, the pendulum including a permanent magnet with an axis of symmetry coinciding with said pendulum axis, the permanent magnet having a direction of magnetization which extends orthogonally to both said pendulum axis and said longitudinal axis; and a Hall effect device having a first axis defining the direction of electric current bias for the device and a second axis along which a Hall voltage is taken, said Hall effect device being mounted to said support means so that said first and second axes extend transversely to said longitudinal axis, said Hall effect device being mounted in symmetrical relation to a plane as defined by said longitudinal axis and said pendulum axis, and above said magnet but spaced apart therefrom.