A two terminal-pair coaxial AC bridge with auto source balance at NIM

A two terminal-pair coaxial AC bridge is constructed at NIM for high precision capacitance transfer, in which, an auto auxiliary source balance method is proposed and achieved. The error introduced by auto source balance circuit is at negligible level. The bridge can transfer capacitance from 1 pF to 100 pF with an uncertainty of 1 × 10
⁻⁸
(k = 1) at low audio frequency.