Linear displacement sensor using a new CMOS double-hall device

A contactless linear displacement sensor for geotechnical purposes, using a new two-output CMOS Hall devise and a high-gradient permanent magnets actuating system, was experimentally tested. The two Hall voltages were taken from neighboring contact. Thus, the magnetosensitivities were equal and opposite in signs and the offsets were nearly equal. A drastic reduction of the residual offset and its temperature drift with more than two orders of magnitude in wide temperature range was achieved. The obtained transducer efficiency of each output was 61 V/AT and the lowest detectable magnetic induction was about 12 μT in a frequency range 1 ≤ f ≤ 102 Hz. The actuating structure contained two barium ferrite permanent magnets directly connected with their repulsive poles. This resulted in doubling of the magnetic flux along to the connecting plane. The linear displacement instrument was with measuring interval 3.0 mm and the error reached no more than 0.3% in the range 10° ≤ T ≤ 40 °C.