Monitoring a rotational angle sensor

A method of monitoring a rotational angle system having a rotational angle sensor operatively coupled to an electric machine, comprising the steps of

• transmitting two amplitude-modulated carrier frequency signals to two stationary windings of the rotational angle sensor;
• providing an input amplifier supplying an output signal at an output thereof, the output signal being substantially equal to zero upon functionally properly generating both carrier frequency signals;
• generating an interference signal alternating for both carrier frequency signals fed to the stationary windings of the rotational angle sensor, thereby creating an interference indication signal at the output of the input amplifier, as a signal that is not equal to zero when no error or no breakage is present within the rotational angle system, and as a signal that is equal to zero when an error or a breakage is present within the rotational angle system.

A circuit assembly for monitoring a rotational angle sensor at an electric machine, said circuit assembly having a control difference unit, a controller connected via an integrator to an amplitude modulator having a sine signal function and a cosine signal function, two multipliers and a carrier frequency generator, wherein said frequency generator is connectable, via two amplifiers, with stator windings of the rotational angle sensor, an excitation winding thereof being connectable to a demodulator via an input amplifier, and comprising a failure detection circuit having a combination of an interference signal generator, a signal analysis circuit and a switch device, wherein the failure detection circuit is connected to the carrier frequency generator.