Method and device for capacitive fill level measurement of liquids or bulk materials

A method for capacitive fill level measurement of liquids and/or bulk materials in a container using at least one measuring sensor that is connected to measuring electronics,

• wherein the measuring sensor is constructed from a plurality of, at least three, electrodes which are electrically insulated from one another and which, for measuring the fill level, are inserted into the container, and in the inserted state extend into the container, and
• wherein these at least three electrodes are connected to the measuring electronics and are adapted to selectively operate in a first measuring mode and a second measuring mode,
• wherein:
• (a) in the first measuring mode, in each case, different potentials are applied to the at least three electrodes of the measuring sensor, wherein a first potential is applied to a first electrode, a second potential that is different with respect to the first potential is applied to a second electrode, and the second electrode is operated as a counter electrode to the first electrode, and a third potential that is different with respect to the first and the second potentials is applied to the third electrode, and the third electrode is operated as a guard electrode;
• and
• (b) in the second measuring mode, a first potential is applied to at least one of the at least three electrodes of the measuring sensor, and at least one second potential that is different with respect to the first potential is applied to either
• an electrically conductive container wall, wherein the measuring electronics and the electrically conductive container wall are galvanically connected to one another, and the electrically conductive container wall is operated as a counter electrode to the at least one electrode of the measuring sensor to which the first potential is applied, or
• to an auxiliary electrode that is separate from the measuring sensor and is arranged within the container or on the outside on the container wall, wherein the measuring electronics and the auxiliary electrode are galvanically connected to one another, and the auxiliary electrode is operated as a counter electrode to the at least one electrode of the measuring sensor to which the first potential is applied, wherein selecting one of the first and second measuring modes takes place by switching between the first and second measuring modes by a switching mechanism.