an inner chamber for accommodating a liquid,

a capacitor arrangement in the inner chamber, wherein the capacitor arrangement has spaced, opposing capacitor surfaces so that at least part of the liquid accommodated in the inner chamber is arranged between the capacitor surfaces,

an evaluation device for supplying an output signal that is at least dependent on a capacitance value of the capacitor arrangement, wherein the evaluation device comprises an excitation circuit and an evaluation circuit,

wherein the excitation circuit has at least one measuring resistor and AC voltage source configured to apply an AC voltage to a series circuit including the measuring resistor and the capacitor arrangement,

wherein the series circuit including the measuring resistor and the capacitor arrangement forms a low-pass filter, and the AC voltage is applied at a frequency in a region of a cutoff frequency of the low-pass filter; and

wherein the evaluation circuit has an output configured to supply the output signal by measuring a voltage across the capacitor arrangement.