Arrangement for establishing and/or monitoring a predetermined filling level in a container

An arrangement for establishing and/or monitoring a predetermined filling level in a container, which arrangement comprises:

• a mechanical oscillatory structure (1), which is fitted at the level of the predetermined filling level,
• piezoelectric elements arranged in a stack,
• of which at least one is a transmitter (3), to which, during operation, an electrical transmission signal is applied via a transmission signal line (5) and which excites the oscillatory structure (1) to produce mechanical oscillations,
• of which one is a first receiver (24a) and one is a second receiver (24b),
• the first and the second receiver (24a, 24b) picking up the mechanical oscillations of the oscillatory structure and converting them into electrical signals (E.sub.1, E.sub.2),
• the first and the second receiver (24a, 24b) each having two electrodes, a first electrode of which is arranged on a surface which bounds the receiver (24a, 24b) in the direction of its polarization and a second electrode of which is arranged on a surface which bounds the receiver (24a, 24b) in a direction opposite to its polarization,
• the electrical signal (E.sub.1) of the first receiver (24a) being picked off via a first signal line (241a), which is connected to the second electrode of the first receiver (24a), and
• the electrical signal (E.sub.2) of the second receiver (24b) being picked off via a second signal line (241b), which is connected to the first electrode of the second receiver (24b),
• an electrical impedance (Z), via which the second signal line (241b) is connected to the transmission signal line (5), and
• a circuit, which produces a reception signal (E) from the two electrical signals (E.sub.1, E.sub.2), which reception signal is equal to the difference between the two electrical signals (E.sub.1, E.sub.2).