Patent ID: 7977935

Claim:
A linear position sensor comprising: a magnetic field strength sensor positioned substantially on a first axis; a first dipole magnet defining a first magnetic axis substantially parallel to the first axis, the first dipole magnet spaced from the first axis in a first direction and extending for a first length parallel to the first axis, and having a first north-south polarity; a second dipole magnet of the first polarity and fixed with respect to and closely spaced from or engaging the first dipole magnet, the second dipole magnet defining a second magnetic axis substantially parallel to the first axis and the first magnetic axis, the second dipole magnet spaced from the first axis in the first direction, and positioned between the first dipole magnet and the first axis, the second dipole magnet extending parallel to the first axis a second length which is between about ¼ to about ¾ that of the first length of the first dipole magnet, and extending symmetrically beyond the first dipole magnet along the first axis, so that the first dipole magnet and the second dipole magnet form a magnetic field which varies substantially linearly along a portion of the first axis on which a perpendicular projection of the second dipole magnet falls; and wherein the magnetic field strength sensor is mounted for movement relative to the first dipole magnet and the second dipole magnet.