METHODS AND APPARATUS FOR PIPETTING AND/OR TITRATING LIQUIDS USING A SELF-CONTAINED AUTOMATED PIPETTE

摘要

METHODS AND APPARATUS FORPIPETTING AND/OR TITRATING LIQUIDS USINGA HAND HELD SELF-CONTAINED AUTOMATED PIPETTEAbstract of the DisclosureA hand held self-contained automated pipettefor portable operation having an electrically operateddigital linear actuator is disclosed. The digital linearactuator preferably includes a stepper motor driving arotor. A threaded screw is coaxially positioned withinthe rotor and is connected to an actuator shaft havingelongate grooves slidable in a guide for preventing act-uator shaft rotation so that precise linear motion is im-parted to the actuator shaft. Provision is made for theremovable attachment of pipetting displacement assembliesof various sizes all actuated by a common digital linearactuator including programmed movement of a displacingpiston in-a displacement cylinder to optimize air inter-face volume neutralize variations in vacuum pipette ef-fects, and provide an accommodated stroke and readout forimproved accuracy while pipetting and/or titrating differ-ent ranges of volumes. A control-circuit is provided sothat the back EMF of the stepper motor coils is recircu-lated when power is duty-cycled off for power conservation.Conversely, recirculation is switched-off when power isduty-cycled on for minimizing losses. Recirculation isswitched off when coils are commutated which produces arapid magnetic field collapse for assuring high torque.Upon calibration the displacing piston undertakes imme-diate excursion to an end of travel limit and after motorslippage is retracted to a home position. This home po-sition is chosen for optimum preservation of an air inter-face volume between drawn liquid and the displacing pis-ton tailored with particularity to the displacement as-sembly being used. Multiple precision modes are providedfor the convenience of the operator, these modes includ-ing pipetting, multiple-dispensing, titration, and dilu-tion. Other features are also disclosed.RRRRR1/9921-2