Patent ID: 7479391

Claim:
Liquid level detection method for a pipetting apparatus ( 1 ) that comprises a fluidic space ( 7 ), to which a pressure transducer ( 11 ) is attached with a gas filled space ( 15 ); the fluidic space ( 7 ) being defined by a pipette tip ( 2 ), a first tubing ( 5 ) that connects the pipette tip ( 2 ) to a pump ( 4 ), and an active part ( 6 ) of the pump ( 4 ); wherein the liquid level detection method comprises the steps of: (a) filling the fluidic space ( 7 ) at least partially with a system liquid ( 8 ) and forming a substantially continuous system liquid column ( 10 ) within the fluidic space ( 7 ); (b) inducing a vertical movement in this system liquid column ( 10 ) by an impulse generating means ( 16 , 18 , 19 ) that is in operative contact with the system liquid column ( 10 ), thereby causing a pressure variation in the gas filled space ( 15 ) that is pneumatically connected with the fluidic space ( 7 ); (c) recording the pressure variation in the gas filled space ( 15 ) with the pressure transducer ( 11 ) and processing the recorded data with a first data processing unit ( 13 ); and (d) deciding according to the processed data, whether a liquid surface ( 17 ) had been penetrated or quitted with an orifice ( 4 ) of the pipette tip ( 2 ).