Pipetting device, fluid processing system and method for operating a fluid processing system

Pipetting device having a tube (1), wherein a liquid space of the tube (1) is at least partially filled with a working fluid (7) which can be operatively connected at a first end of the tube (1) to a pressure-generating means, designed for aspirating or dispensing a sample liquid (4′) via an opening (3) provided at a second end of the tube (1), wherein the working fluid (7) and the sample liquid (4′) are electrically insulated from one another via an air gap (8), wherein a first electrode (5) is formed on the pipetting device, which, together with a second electrode (4′) formed by at least a part of the sample liquid (4′) that can be accommodated in the tube, forms a measuring capacitor (6) which can be operatively connected to a measuring unit (CAP) which is designed, as a function of the capacitance of the measuring capacitor (6), to determine a volume of the aspirated or dispensed sample liquid (4′), further comprising a first electrical contact (9′) which is electrically insulated from the first electrode (5) and the second electrode (4′) and adapted to establish an electrical connection with the working fluid (7), wherein the first electrical contact (9′) is electrically connectable to the measuring unit (CAP) via a low-impedance converter circuit (WS).