Implementation of a graphene impedance quantum standard with an electronic fully digital impedance bridge

The units of electrical impedance can be realized by using the quantum Hall resistance at AC (ACQHR). Impedance traceability chains based on the ACQHR can be obtained by exploiting novel digital impedance bridges. An affordable and easy-to-operate impedance quantum standard can be obtained by combining graphene quantum Hall resistance standards in the AC regime and these novel digital impedance bridges. We developed a four-terminal-pair electronic digital impedance bridge able to calibrate a capacitance standard directly against a graphene ACQHR standard with a relative uncertainty of about 1x10^-7 to implement the future INRIM traceability chain of the farad. The working principle, implementation, validation and uncertainty evaluation of the electrical fully digital impedance bridge for the calibration of a capacitance standard against a graphene ACQHR standard developed at INRIM are herewith discussed.