Improved Horizontal Cross Capacitor

A new horizontal cross capacitor was constructed to achieve higher accuracy in the determination of absolute capacitance values. To eliminate some major causes of the uncertainty that had been found in the earlier capacitor, the bars were finished more precisely and new mechanisms were adopted. These are a fine adjusting mechanism for alignment of the bars and a supporting mechanism of the bars that prevents them from bending because of gravity. A nonrotating guard-tube driving mechanism was used. The bars could be aligned within 0.1 pm or less. The alignment was inspected with capacitance-type electronic micrometers. The bending dip of the bars was estimated to be negligibly small. The uncertainty in the absolute determination of 0.2 pF with this capacitor is estimated to be of the order of 10-7.