Vibronic Sensor

A method to determine and/or monitor at least one process variable of a medium with at least one vibration-capable unit, comprising the steps of:

• exciting the vibration-capable unit to mechanical vibrations by means of an electrical excitation signal of an adjustable frequency;
• transducing the mechanical vibrations into a received electrical signal, which received electrical signal is characterized at least by a frequency and/or a phase and/or an amplitude, said electrical excitation signal is generated based on said received signal;
• sampling the voltage values of said received electrical signal at specified predetermined points in time, starting from said electrical excitation signal;
• determining the real part and imaginary part of said received electrical signal from the sampled voltage values of said received signal by means of a Goertzel algorithm, wherein at least one Goertzel coefficient—in particular the number of the sample values and/or an operating frequency and/or a sample frequency—is provided for performing the Goertzel algorithm;
• calculating at least the current phase and/or the current amplitude of said received electrical signal from said real part and imaginary part of said received electrical signal;
• and
• adjusting the frequency of said electrical excitation signal such that a predeterminable phase shift is present between said electrical excitation signal and said received electrical signal, and wherein the at least one process variable is determined.

A device to determine and/or monitor at least one process variable of a medium, comprising:

• at least one mechanical vibration-capable unit;
• a control unit;
• an electromechanical transducer unit which is designed to excite said at least one mechanical vibration-capable unit to mechanical vibrations based on an electrical excitation signal of an adjustable frequency, and to receive the mechanical vibrations and transduce them into a received electrical signal, which received signal is characterized at least by a frequency and/or a phase and/or an amplitude;
• and
• an electronic unit with a microprocessor which is designed:
• to generate the electrical excitation signal based on the received signal, to sample the voltage values of the received signal at defined predetermined points in time, to determine the real part and imaginary part of the received signal from the sampled voltage values of the received signal by means of a Goertzel algorithm, wherein:
• at least one Goertzel coefficient—in particular the number of the sample values and/or a working frequency and/or a sample frequency—is provided for performing the Goertzel algorithm, to calculate at least the current phase and/or the current amplitude of the received signal from the real part and imaginary part of the received signal;
• with said control unit that is designed to set the frequency of the excitation signal such that a predeterminable phase shift is present between the excitation signal and received signal;
• and
• said electronic unit is designed to determine the at least one process variable.