Fig. 1.

Electrodes attached to the exterior of a freeze-drying vial. A active electrode, B guard electrode, C connector strip from the elecrode to the neck of the vial, D miniature co-axial wire connecting the electrode to the measuring system (where the outer braiding of the coaxial cable attaches to the guard electrode and the inner conductor attaches either to the stimulating or current sensing electrode), Φ ratio of liquid fill height to the height of the top of the guard electrode