Fill level monitoring

A monitoring circuit for the fill level monitoring of a collecting vessel, which is capable of being filled with a dielectric medium, the monitoring circuit comprises:

• at least one measuring capacitor which can be assigned to a collecting vessel such that a capacitance of said measuring capacitor is steadily changing in correlation with a fill level at least over a fill level range of the collecting vessel, wherein the monitoring circuit is configured such that the capacitance of the measuring capacitor and a quality factor of the measuring capacitor is ascertained and conclusions are drawn as to a permittivity of the dielectric medium on a basis of the ascertained quality factor of the measuring capacitor, wherein a fill level of the dielectric medium in the collecting vessel is ascertained as a function of the ascertained capacitance of the measuring capacitor and the ascertained permittivity of the dielectric medium, the monitoring circuit further including the quality factor of the measuring capacitor being ascertained by determining a difference between output voltages of the monitoring circuit before and after a change in an operating point or a circuit quality factor of the monitoring circuit, wherein the monitoring circuit further includes a switched capacitor element (SC element) that includes the measuring capacitor and at least one switching module and wherein in order to change the operating point or the circuit quality factor, at least one ohmic resistor in series with the at least one switching module is increased or a pulse/pause ratio of a switching frequency for the SC element is changed.