Vibronic sensor with reduced facility for gas blasting

A device for determining or monitoring at least one process variable of a medium, comprising:

• a mechanically vibratable unit, a drive/receiver unit, and an electronics unit;
• wherein at least a first piezoelectric element and a second piezoelectric element serve as the drive/receiver unit;
• wherein the mechanically vibratable unit is a vibrating fork including a diaphragm, a first vibrating element and a second vibrating element;
• wherein the first vibrating element and the second vibrating element are integrally formed on the diaphragm;
• wherein the first piezoelectric element is at least partially arranged in the first vibrating element and the second piezoelectric element is at least partially arranged in the second vibrating element;
• wherein the drive/receiver unit is designed to excite the mechanically vibratable unit to produce mechanical vibrations by means of an electrical excitation signal, and to receive the mechanical vibrations of the mechanically vibratable unit and convert them into a first reception signal;
• wherein the first piezoelectric element is designed to emit an ultrasonic transmission signal;
• wherein the second piezoelectric element is designed to receive the ultrasonic transmission signal in the form of a second reception signal;
• wherein the electronics unit is designed to generate the excitation signal on the basis of the first reception signal, to set a frequency of the excitation signal in such a way that there is a predeterminable phase shift between the excitation signal and the first reception signal, and to determine the at least one process variable using the first reception signal and/or the second reception signal;
• and
• wherein a surface of the diaphragm facing toward the process is curved by being concave.