Inductive sensor with monitoring of the excitation signal

An inductive sensor comprising:

• an oscillator to generate a sinusoidal excitation signal having a first excitation frequency;
• a resonant circuit connected to the oscillator and configured to be excited by the excitation signal to generate an electromagnetic field;
• a coupling element, movable relative to the resonant circuit, to change the electromagnetic field as a function of a length or a rotation angle;
• a sensor to generate an electrical sensor signal as a function of the electromagnetic field;
• a measuring transducer to generate a measuring transducer output signal as a function of the electrical sensor signal, which represents the length or the rotation angle;
• and
• a checking filter to check a sinusoidal form of the excitation signal,
• wherein the checking filter for checking the sinusoidal form includes a bandpass filter, whose pass band is selected such that the bandpass filter allows frequency portions of a signal in a range of the first excitation frequency to pass, and wherein the bandpass filter has an input that is connected to an output of the oscillator,
• wherein the checking filter for checking the sinusoidal form includes a rectifier, which has an input which is connected to an output of the bandpass filter, and
• wherein the checking filter for checking the sinusoidal form includes a comparison unit, which has an input connected to an output of the rectifier or an output of a FFT unit, the comparison unit comparing an output signal of the rectifier or an amplitude of a fundamental frequency in an output signal of the FFT unit with a predefined value.