A pipette module for a liquid handling system including a liquid-handling-system z-axis frame, at least one container with a container open end having a predetermined container-open-end position (R 1) relative to the liquid-handling-system z-axis frame, a liquid in the at least one container having a liquid surface with an unknown liquid surface level (R 2), the pipette module comprising: a pipette-module frame attachable to the liquid-handling-system z-axis frame; a pipette-module translatory-motion frame attached to the pipette-module frame and movable with respect to the pipette-module frame by a pipette-module motor; a pneumatic aspirator assembly comprising: a pipette-module cylinder having a piston movably disposed therein; a tube in fluid communication with the pipette-module cylinder, the tube terminating in a tip; and a pressure sensor in fluid communication with the cylinder, the tube and the tip; and a pipette-module controller in electrical communication with the pipette-module motor and the pressure sensor, characterized in that: the pipette-module cylinder, the tube and the tip are attached to the pipette-module translatory-motion frame and movable therewith; the piston is fixedly attached to the pipette-module frame by a piston rod; and the pipette-module controller has a liquid surface detection mode of operation which enables a pressure feedback control algorithm that causes the pipette-module motor to move the pipette-module translatory-motion frame in a z-axis translatory motion until a change in a pressure in the tip as sensed by the pressure sensor indicates that the tip is in contact with the liquid surface. a pipette-module frame attachable to the liquid-handling-system z-axis frame; a pipette-module translatory-motion frame attached to the pipette-module frame and movable with respect to the pipette-module frame by a pipette-module motor; a pneumatic aspirator assembly comprising: a pipette-module cylinder having a piston movably disposed therein; a tube in fluid communication with the pipette-module cylinder, the tube terminating in a tip; and a pressure sensor in fluid communication with the cylinder, the tube and the tip; and a pipette-module cylinder having a piston movably disposed therein; a tube in fluid communication with the pipette-module cylinder, the tube terminating in a tip; and a pressure sensor in fluid communication with the cylinder, the tube and the tip; and a pipette-module controller in electrical communication with the pipette-module motor and the pressure sensor, characterized in that: the pipette-module cylinder, the tube and the tip are attached to the pipette-module translatory-motion frame and movable therewith; the piston is fixedly attached to the pipette-module frame by a piston rod; and the pipette-module controller has a liquid surface detection mode of operation which enables a pressure feedback control algorithm that causes the pipette-module motor to move the pipette-module translatory-motion frame in a z-axis translatory motion until a change in a pressure in the tip as sensed by the pressure sensor indicates that the tip is in contact with the liquid surface. the pipette-module cylinder, the tube and the tip are attached to the pipette-module translatory-motion frame and movable therewith; the piston is fixedly attached to the pipette-module frame by a piston rod; and the pipette-module controller has a liquid surface detection mode of operation which enables a pressure feedback control algorithm that causes the pipette-module motor to move the pipette-module translatory-motion frame in a z-axis translatory motion until a change in a pressure in the tip as sensed by the pressure sensor indicates that the tip is in contact with the liquid surface.