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Rotational speed detection is one of the most essential sensor tasks in today's cars. It is used to determine the position of the crank-and camshaft as well as for the control of the wheel speed in ABS applications. In the last years, the general demand for less fuel consumption and less exhaust emissions has yielded harsher requirements particularly for crankshaft sensors. One of the most promising approaches for rotational speed detection is the use of magnetoresistive sensors in front of a turning gear wheel. These sensors offer a high sensitivity to magnetic fields. Furthermore, the high signal-to-noise-ratio results in a very small phase error due to phase jitter. This makes the use of MR-technology very attractive for revolution counting with the parallel implementation of additional features, such as misfire detection, for example. In the proximity of new engine components like the integrated starter generator, which cause large disturbing magnetic fields, these sensors require magnetic shielding in order to produce a correct output signal. For this reason, a new generation of engine speed sensors is under development, which combines the described advantages of magnetoresistive technology with a high robustness against disturbances caused by external magnetic fields due to neighbouring engine components. INTRODUCTIONThe property of a current-carrying magnetic material to change its resistivity ρ in the presence of an external magnetic field H is called the magnetoresistive (MR) effect. The effect has been described previously [1]. Because the magnetoresistive effect is a nonlinear effect by nature, a number of magnetoresistive sensors use a 'barber-pole' construction to linearize the R − H relationship, incorporating slanted stripes of a good conductor to rotate the current. This type of sensor has the widest range of linearity and the least associated distortion than any other form of linearization. The characteristic of a magnetoresistive element with barberpole-stripes is plotted in figure 1 (curve a)). It can be seen, that for small values of the magnetic field strength H, the R − H dependence is quasi-linear. By rotation of the barberpole stripes the characteristic of the resistor can be inverted (curve b). For the realisation of a rotational speed sensor, typically four

A programmable angular measurement system with online diagnosis is presented. The actual measurement principle is based on the anisotropic magnetoresistive effect. The sensing element provides a sine-and a cosine-signal related to the applied magnetic field angle. The signal conditioning algorithm calculates the magnetic field angle from these signals by using the CORDIC algorithm. Additionally, a variety of diagnosis features are implemented in order to ensure a fail-safe operation of the device. The sensor is thus particularly suited for applications under harsh environmental conditions as found in automobiles.Es wird ein programmierbares Winkelmesssystem mit Online-Diagnose vorgestellt. Das Messprinzip beruht auf dem anisotropen magnetoresistiven Effekt. Bei Anlegen eines Magnetfeldes erzeugen zwei gegeneinander verdrehte Messbrücken je ein Sinus-und ein Kosinus-Signal, welches in der Signalverarbeitungseinheit mit Hilfe des CORDIC-Algorithmus verarbeitet wird. Um einen sicheren Betrieb des Messsystems zu gewährleisten, wurde eine Vielzahl von Diagnosefunktionen in den Sensor integriert. Er ist daher besonders für den Betrieb unter extremen Umweltbedingungen wie bspw. im Automobil geeignet.