Determining a waste water filling level in a vehicle tank, measuring arrangement and waste water arrangement

A method for determining a filling level (F) of waste water in a tank onboard a vehicle, wherein a respective flushing quantity (P) of waste water is fed to the tank by means of flushing processes,

• wherein:
• a binary filling signal (La-e) which indicates whether waste water is present there or not is determined at at least two different measuring positions at the tank, wherein the associated filling quantities (Ma-e) of the tank at the measuring positions are known and different,
• the filling level (F) is determined as a sum of a basic filling quantity (B) and an inflow quantity (Z), wherein:
• if none of the filling signals (La-e) is active:
• the basic filling quantity (B) is selected as zero, and
• otherwise all the currently active filling signals (La-e) and the associated filling quantities (Ma-e) are determined, and the largest of the determined filling quantities (Ma-e) is selected as the basic filling quantity (B),
• a starting time (A) for the determination of the inflow quantity (Z) is selected as a time at which the basic filling quantity (B) is reached in the tank,
• the inflow quantity (Z) is determined as a sum of all the flushing quantities (P) which are fed to the tank from the starting time (A), and
• the determined filling level is used to perform either an activation operation for the flushing processes or deactivation operation for the flushing processes.