Magnetoresistive Sensors for High Resolution Position Encoding

For the measurement and control of angular position or rotational speed in automobiles, the environmental conditions have led manufacturers to mainly specify magnetic sensors. They are able to withstand high shock and vibration, the presence of oil, dust or salt spray, and can operate over a temperature range as wide as -40°C to +150°C. Magnetic sensors generally meet these goals better than optical devices. Increasingly, though, modern engine control requirements call for much higher resolutions, and this paper describes how the environmental conditions are accomplished in a high resolution magnetic device. Three different configurations that are applicable to automobiles are described: a stand-alone encoder mounting to a stub shaft, a stand-alone encoder mounting over a through shaft, and a modular encoder comprising independent encoder wheel and sensor components.