Abstract: A hand held self-contained automated pipette for portable operation having an electrically operated digital linear actuator. The actuator preferably includes a stepper motor driving a rotor. A threaded screw is coaxially positioned within the rotor and is connected to an actuator shaft having elongate grooves slidable in a guide for preventing shaft rotation so that precise linear motion is imparted to the shaft. A pipetting displacement assembly having one of various sizes is removably attached for actuation by a common actuator including programmed movement of a displacing piston in a displacement cylinder to optimize air interface volume, neutralize variations in vacuum pipette effects, and provide an accommodated stroke and readout for improved accuracy while pipetting and/or titrating different ranges of volumes. Upon calibration the piston undertakes immediate excursion to an end of travel limit and after motor slippage is retracted to a home position.