Traceability Chain at KRISS from DC Quantum Hall Resistance to Farad Using Coaxial Bridges

A national traceability chain from dc quantum Hall resistance (QHR) to capacitance has been established at Korea Research Institute of Standards and Science using various impedance standards and coaxial bridges. An ac-dc calculable resistance standard of nominal value of 12.9 kΩ was used as a transfer standard from dc to ac at the frequency of 1.541 kHz. Two ac coaxial bridges, developed by INRiM, were employed: a ratio bridge, linking the 103-kΩ ac resistor to the 12.9-kΩ ac-dc calculable resistor calibrated in terms of the dc QHR and a quadrature bridge, calibrating the 1000 pF capacitors versus the 103-kΩ ac resistors. The ratio bridge defines the 103-kΩ resistor as a two-terminal-pair (2TP) standard and the 12.9-kΩ resistor as a four-terminal-pair standard; a cable correction was applied to the 2TP defined standard. The stability of all standards has been monitored for more than 3 years to be within a few parts in 10⁶. The capacitance value, obtained with the new traceability chain, shows an agreement (a few parts in 10⁷) in a comparison with the reference values, traced from the National Institute for Standards and Technology (USA).