Liquid transfer module for a chemical analyzer

A liquid transfer module for a chemical analyzer is adequate to effect liquid transfers between multiple stations arranged in a common arc about a vertical axis on a supporting instrument framework. A rigid radial probe arm supporting a vertical pipette is fixed to a tubular shaft supported on the framework for both rotational and elevational motion relative to the vertical axis. It is surrounded by a powered pulley that imparts angular movement to the shaft. It is elevationally carried by a non-rotating bearing assembly arranged coaxially about the axis on a nut threadably engaged by a powered lead screw extending within the confines of the shaft. Both the elevational and angular positions of the shaft are electronically monitored.