An apparatus includes a shaft and a first code ring including a first number of pole pairs. The first code ring is attached to the shaft. The apparatus includes a second code ring including a second number of pole pairs different from the first number. The second code ring is attached to the shaft and...http://www.google.de/patents/US8085036?utm_source=gb-gplus-sharePatent US8085036 - Sensor including two code rings and a magnetic field sensor between the code rings
