Abstract: The invention relates to a field device for detecting or monitoring a physical or chemical process variable of a medium in automation technology, having a power output (6), which is arranged on the primary side (P), and having an electronics unit (3, 13) which is arranged on the secondary side (S) and is supplied with energy from the primary side (P) via two connecting lines (4), wherein the electronics unit (3) actuates the power output (6) such that the direct current flowing on the connecting lines (4) represents the value of the process variable which is detected on the secondary side (S), having at least one communications unit (7) which provides digital data (Data), and having a galvanically decoupled transmission means (9) which transmits the digital data (Data) between the primary side (P) and the secondary side (S), wherein a circuit arrangement having two switches of a primary-side switch pair (11) is provided, wherein one switch of the primary-side switch pair (11) is arranged in each connecting li

Abstract: A method and an apparatus for determining or monitoring a predetermined fill level, a phase boundary or a density of a medium in a container with an oscillatable unit. The oscillatable unit is placed at the height of the predetermined fill level and is excited to oscillate successively with discrete exciter frequencies following one another in a frequency scanning operation (sweep) within a predeterminable frequency band in the working range of the oscillatable unit. The corresponding oscillations of the oscillatable unit are received in the form of received signals; wherein that exciter frequency is ascertained in the frequency scanning operation, at which the oscillatable unit oscillates with an oscillation frequency, which has a predetermined phase shift between the transmission signal and the received signal; and wherein the transmitting/receiving unit excites the oscillatable unit to oscillate with the ascertained oscillation frequency.

Abstract: A method and an apparatus for determining or monitoring a predetermined fill level, a phase boundary or a density of a medium in a container with an oscillatable unit. The oscillatable unit is placed at the height of the predetermined fill level and is excited to oscillate successively with discrete exciter frequencies following one another in a frequency scanning operation (sweep) within a predeterminable frequency band in the working range of the oscillatable unit. The corresponding oscillations of the oscillatable unit are received in the form of received signals; wherein that exciter frequency is ascertained in the frequency scanning operation, at which the oscillatable unit oscillates with an oscillation frequency, which has a predetermined phase shift between the transmission signal and the received signal; and wherein the transmitting/receiving unit excites the oscillatable unit to oscillate with the ascertained oscillation frequency.