Quasi-monolithic toroidal cross-capacitor

A quasi-monolithic toroidal cross-capacitor has been developed as an extremely stable and reliable capacitance standard of 0.5 pF. A geometrically symmetrical electrode structure is realized by using two identical plated substrates produced from fused silica with an exceedingly low thermal expansion coefficient. The capacitance instability expected after finishing the aging process does not exceed 5 /spl times/ 10/sup -8/ per year. Investigations have shown that the capacitor developed for evaluation of the frequency dependence of the calculable cross-capacitor developed by Korea Research Institute of Standards and Science (KRISS), Daejeon, Korea, can be used as a substitute to maintain the capacitance unit, as well as a loss angle standard and a transfer standard to carry out intercomparisons.