| 摘要 |
A device for determining and/or monitoring at least one process variable of a medium (2) in a container (2a) comprising at least one sensor unit (3) and one electronic unit (6), wherein the sensor unit (3) comprises at least one mechanical oscillatory unit (4), and a drive/receiving unit (5) comprising at least one piezoelectric element (18) with at least one transmitting electrode (19, 19a) for exciting the mechanical oscillatory unit (4) to mechanical oscillations by means of an electrical excitation signal (UA) and at least one receiving electrode (20, 20a) for receiving the mechanical oscillations of the mechanical oscillatory unit (4) and for converting the mechanical oscillations into an electric receiving signal (UE), and wherein the electronic unit (6) comprises at least one control unit (10) for setting a predeterminable phase shift (Δφ) between the excitation signal (UA) and the receiving signal (UE), at least one adjustable capacitor (CE, 9) arranged parallel to the control unit (10), and at least one computer unit (15) which is equipped to determine the at least one process variable from the receiving signal (UE), and to set the position of the anti-resonance frequency (fanti) of the mechanical oscillatory unit (4) by means of the adjustable capacitor (CE, 9). |
