Patent ID: 7199578

Claim:
A measuring device comprising: a Hall sensor for displacement measurements; and a magnetic tube, wherein the Hall sensor is disposed centrally and in an axially movable manner in said magnetic tube, a first half of said magnetic tube being cross-magnetized in a first direction such that said first half includes a first magnetic north pole diametrically opposed to a first magnetic south pole, and a second half of said magnetic tube being cross-magnetized in a second direction opposite said first direction such that said second half includes a second magnetic north pole diametrically opposed to a second magnetic south pole; and wherein the first magnetic north poles on said first half of said tube is diametrically opposed to said second magnetic north pole on said second half of said tube, and said first magnetic south pole on said first half of said tube is diametrically opposed to said second magnetic south pole on said second half of said tube.