Device for determining and/or monitoring at least one process variable of a medium comprising a sensor unit with a mechanically vibrating unit, and at least one first piezoelectric element, and with electronics wherein the device is designed for this purpose, to excite the mechanically vibrating unit to mechanical vibrations by means of an excitation signal, to receive the mechanical vibrations of the vibrating unit and convert them into a first received signal, a to transmit a transmit signal and to receive a second receive signal (E S), and wherein the electronics is designed to determine the at least one process variable using the first (E A) and/or second received signal (E S), characterised in that in that the sensor unit also has a unit for determining and/or monitoring a temperature of the medium, in that the unit for determining and/or monitoring the temperature comprises a first and a second temperature sensor, which first and second temperature sensor are arranged at a distance from one another, in that the electronics is designed to determine the temperature of the medium on the basis of a first and/or second temperature reception signal of the first and/or second temperature sensor received by the unit, in that the first temperature sensor is arranged and/or designed to detect a first temperature in a first end region of the sensor unit facing the medium, and in that the second temperature sensor is arranged and/or designed to detect a second temperature in a second end region of the sensor unit facing away from the medium, in particular in a region in which the at least one piezoelectric element (11a, 11b) is arranged. a sensor unit with a mechanically vibrating unit, and at least one first piezoelectric element, and with electronics wherein the device is designed for this purpose, to excite the mechanically vibrating unit to mechanical vibrations by means of an excitation signal, to receive the mechanical vibrations of the vibrating unit and convert them into a first received signal, a to transmit a transmit signal and to receive a second receive signal (E S), and wherein the electronics is designed to determine the at least one process variable using the first (E A) and/or second received signal (E S), characterised in that in that the sensor unit also has a unit for determining and/or monitoring a temperature of the medium, in that the unit for determining and/or monitoring the temperature comprises a first and a second temperature sensor, which first and second temperature sensor are arranged at a distance from one another, in that the electronics is designed to determine the temperature of the medium on the basis of a first and/or second temperature reception signal of the first and/or second temperature sensor received by the unit, in that the first temperature sensor is arranged and/or designed to detect a first temperature in a first end region of the sensor unit facing the medium, and in that the second temperature sensor is arranged and/or designed to detect a second temperature in a second end region of the sensor unit facing away from the medium, in particular in a region in which the at least one piezoelectric element (11a, 11b) is arranged.