Abstract: An electrode holder assembly is provided for holding test electrodes in a sample container. The assembly comprises a vertically aligned lead screw mounted to rotate freely, and a nut, inserted over the lead screw, adapted to move freely over the length of the lead screw when subject to a vertical force. A collet that extends upward from the nut body is biased inwardly by a spring so as to secure a friction fit, substantially free of any backlash movement, between the nut and the lead. Attached to the nut is an electrode holder platform having mounting bores adapted for securing test electrodes therethrough. This assembly allows the test electrodes to be moved up or down, for insertion and removal from a test solution, by one-handed vertical activation of the electrode holder platform. The lead screw, nut, and associated components may all be housed in a tower assembly so that only the electrode platform is exposed.

Abstract: A friction chuck for securing a test probe within a platform holder. The chuck, formed of elastomeric material, comprises a chuck body with an axially extending bore and a plurality of downward extending fingers disposed around the outer circumference of the projection of the chuck bore. Each finger has an interior bulge that extends into the projection of the chuck bore. The bulges define a segmented aperture of a diameter less than the diameter of the chuck base. When a test probe is inserted into the chuck bore it engages the fingers and bends them outwardly. There is sufficient friction between the fingers and the test probe so that the probe is secured by the fingers. The fingers have sufficient flexibility so the probe position may be changed by hand adjustment.