The output switches precisely when the difference in magnetic field strength between the two Hall-effect elements is zero. Coupled with a back-biasing magnet, the sensor can turn on or off with the leading or trailing edge of a gear tooth or slot. Differential sensing provides immunity to radial vibration and an on-chip bandpass filter eliminates system offsets. Applications include speed sensing in automotive crankshafts using ring magnets.

Allegro Microsystems,
115 Northeast Cutoff, Worcester, MA 01606,
(508) 853-5000,