Pipetting unit with capacitive liquid detection, combination of such a pipetting unit and a pipetting tip, and method for capacitively detecting pipetting liquid

A pipetting unit configured for capacitive liquid detection, comprising:

• a pressure tube;
• a shield disposed around the pressure tube and movably supported relative to the pressure tube;
• a coupling configured to temporarily attach a pipetting tip to the pipetting unit, wherein attachment of the pipetting tip to the coupling establishes an electrical connection between the pressure tube and the pipetting tip;
• an ejection spring arranged at an end portion of the shield distal from the pipetting tip, wherein the shield is movable to exert an ejection force on the pipetting tip via the ejection spring;
• and
• an electric circuit electrically coupled to the pressure tube and, via the ejection spring, to the shield,
• wherein the electric circuit is configured to apply a time-variable electrical signal to the pressure tube, said time-variable electrical signal enabling capacitive detection of a contact between the pipetting tip and a pipetting liquid when the pipetting tip is attached, and wherein the electric circuit is configured to connect the shield to ground via the ejection spring.