Apparatus for determining and/or monitoring at least one process variable of a medium

An apparatus for determining and monitoring at least a first process variable of a medium, comprising:

• an electronics unit;
• and
• a sensor unit,
• wherein the electronics unit is embodied to supply the sensor unit with an excitation signal composed of an excitation carrier signal having an excitation carrier frequency and an excitation modulation signal having an excitation modulation frequency and to receive from the sensor unit a received signal composed of a received carrier signal and a received modulation signal,
• and wherein the electronics unit is further embodied to measure a phase shift between the excitation modulation signal and the received modulation signal and to determine from the phase shift the first process variable.

A method for determining and monitoring a first process variable of a medium, comprising:

• providing an electronics unit and a sensor unit;
• supplying from the electronics unit to the sensor unit an excitation signal composed of an excitation carrier signal having an excitation carrier frequency and an excitation modulation signal having an excitation modulation frequency;
• receiving by the electronics unit from the sensor unit a received signal composed of a received carrier signal and a received modulation signal;
• and
• determining from a phase shift between the excitation modulation signal and the received modulation signal the first process variable.