Measuring device

A measuring device for a non-electrical variable, comprising:

• a measuring unit which indirectly converts the non-electrical variable into an electrical measurement signal via an electrical alternating current having a frequency, the electrical measurement signal including a signal portion at a double frequency dependent on the non-electrical variable, and a fault signal portion having the frequency dependent on the alternating current;
• a signal pre-processing device which pre-processes and digitizes the measurement signal to obtain a digital signal;
• and
• a signal processing device which processes the digital signal via signal processing software to generate a measured value;
• wherein the signal processing software is implemented to:
• detect the digital signal in a phase-sensitive manner, by multiplication with a reference signal at the double frequency, and process said digital signal by subsequent low-pass filtering to generate the measured value, which is proportional to the non-electrical variable;
• and
• detect the digital signal in a phase-sensitive manner, by multiplication with a further reference signal at the single frequency, and process said digital signal by subsequent low-pass filtering to generate a fault signal value;
• wherein the signal processing device includes a normalizing stage, which normalizes the measured value by forming the quotient using the square of the fault signal value, and outputs said measured value as a normalized measured value.