Procedure for monitoring the state at least of a component (3, 4) of an electromechanical resonator with at least a piezoelectric element, which can be excited to produce mechanical vibrations by means of an electrical excitation signal (A A), and whose mechanical vibrations can be received in the form of an electrical reception signal (A E), wherein said procedure comprises the following steps: - at a first point in time (ti): a. Determination of an amplification factor (V 90) of the electromechanical resonator, b. Determination of a mechanical quality of the electromechanical resonator ■ on the basis of a slope of a phase shift (Δφ) between the excitation signal (A A) and the reception signal (A E) as a function of a frequency (ω) in the presence of a resonance vibration with a resonance frequency (ω 90), ■ on the basis of the change over time of the amplitude of the reception signal (A E) following the deactivation of the excitation signal (A A), or ■ on the basis of a modulation of the excitation signal (A A), and c. Determination of an electromechanical efficiency (k(ti)) of the electromechanical resonator at least from the amplification factor (V 90) and the mechanical quality, - Repetition of the procedural steps a) - c) at least at a second point in time (t 2) - Calculation of a change over time of the electromechanical efficiency (Δk(t)) on the basis of a comparison between at least the electromechanical efficiency (k(ti)) determined at the point in time (ti) and the electromechanical efficiency (k(t 2)) determined at the point in time (t 2), and - Comparison of the change over time of the electromechanical efficiency (Δk(t)) with a predefinable limit value (Δk) for the change in electromechanical efficiency (Δk(t)), and determination of a state indicator from the comparison. - at a first point in time (ti): a. Determination of an amplification factor (V 90) of the electromechanical resonator, b. Determination of a mechanical quality of the electromechanical resonator ■ on the basis of a slope of a phase shift (Δφ) between the excitation signal (A A) and the reception signal (A E) as a function of a frequency (ω) in the presence of a resonance vibration with a resonance frequency (ω 90), ■ on the basis of the change over time of the amplitude of the reception signal (A E) following the deactivation of the excitation signal (A A), or ■ on the basis of a modulation of the excitation signal (A A), and c. Determination of an electromechanical efficiency (k(ti)) of the electromechanical resonator at least from the amplification factor (V 90) and the mechanical quality, a. Determination of an amplification factor (V 90) of the electromechanical resonator, b. Determination of a mechanical quality of the electromechanical resonator ■ on the basis of a slope of a phase shift (Δφ) between the excitation signal (A A) and the reception signal (A E) as a function of a frequency (ω) in the presence of a resonance vibration with a resonance frequency (ω 90), ■ on the basis of the change over time of the amplitude of the reception signal (A E) following the deactivation of the excitation signal (A A), or ■ on the basis of a modulation of the excitation signal (A A), and ■ on the basis of a slope of a phase shift (Δφ) between the excitation signal (A A) and the reception signal (A E) as a function of a frequency (ω) in the presence of a resonance vibration with a resonance frequency (ω 90), ■ on the basis of the change over time of the amplitude of the reception signal (A E) following the deactivation of the excitation signal (A A), or ■ on the basis of a modulation of the excitation signal (A A), and c. Determination of an electromechanical efficiency (k(ti)) of the electromechanical resonator at least from the amplification factor (V 90) and the mechanical quality, - Repetition of the procedural steps a) - c) at least at a second point in time (t 2) - Calculation of a change over time of the electromechanical efficiency (Δk(t)) on the basis of a comparison between at least the electromechanical efficiency (k(ti)) determined at the point in time (ti) and the electromechanical efficiency (k(t 2)) determined at the point in time (t 2), and - Comparison of the change over time of the electromechanical efficiency (Δk(t)) with a predefinable limit value (Δk) for the change in electromechanical efficiency (Δk(t)), and determination of a state indicator from the comparison.