Allegro Microsystems is advocating GMR – giant magneto-resistive – effect sensors instead of Hall effect for automotive rotary wheel position sensing.

The company, which makes both Hall and GMR sensors, argues that GMR has lower noise and therefore reduces angular jitter when measuring the position of rotating shafts.

“GMR is fundamentally a lower-noise magnetic sensing technology than Hall effect for magnetic sensor ICs,” Allegro told Electronics Weekly. “Both GMR and Hall are effectively transducers that convert magnetic flux density into voltage. Allegro GMR provides more than 50 times the voltage per gauss and as ICs always have a noise floor – such as from thermal noise – GMR provides higher SNR.”

It sees Hall sensors producing a speed accuracy within 0.5 to 2% if speed is deduced from two adjacent output pulses, and them operating with an allowable air gap of ~2 to 3mm – depending on the target type. “These sensors have met the needs of standard braking systems,” said Allegro

source:electronics weekly.com