Eppendorf Ag

Eppendrof Ag

Gerhard Salje

Boris Von Beichmann

Jorg Richter

A liquid proportioning method using a chamber for a gas and a reception volume connectable thereto for a liquid with an aperture to the environment, wherein a desired volume is predetermined for the liquid to be taken up by the reception volume, a chamber negative pressure is determined which has to exist in the chamber to cause the desired liquid volume to be taken up in the reception volume after the aperture is dipped into the liquid and the chamber is connected to the reception volume, the chamber negative pressure is produced in the chamber, the reception volume dips its aperture into the liquid, and the chamber is connected to the reception volume and the desired volume of the liquid is taken up in the reception volume.

Liquid proportioning method and apparatus for implementing the method

A method for controlled proportioning of liguids with a postive-displacement device ( ) for dislocating a gas cushion ( ) includes measuring the pressure (p ) in the gas cushion ( ) at the time of a complete discharge of a liquid volume, measuring the discharge time (t ) for a complete discharge of the liquid volume and determining the time demand (&Dgr;t) to compress the gas cushion ( ) by the postive-displacement device by means of the pressure (p ), the dead volume (V ) of the gas cushion ( ), a gas condition equation, and the volumetric gas flow (Q) discharged by the postive-displacement device. A corrected discharge time (t ) is determined as a proportioning control magnitude by a deduction of the time demand (&Dgr;t) from the measured dischage time (t ) with outputting, and/or saving, and/or resorting to the deviation of the corrected discharge time (t ) from a desired discharge time (t ) for regulating the discharge of the liquid volume.

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Hamburg, Germany

Gerhard Salje