Cryogenic Current Comparator (CCC)

Automated Cryogenic Current Comparator (CCC) Bridges for Quantum Metrology and Resistance Calibrations

Overall system accuracy: better than 1 in 10⁸

NPL and Cryogenic Ltd. have been involved in the development of cryogenic current comparator (CCC) technology for over two decades and have built up internationally recognised expertise in this field.  A resistance bridge based on a CCC using a SQUID as a null detector allows the metrologist to exploit fully the accuracy of the quantum Hall effect as a primary standard of resistance. At the same time, an automated CCC bridge is ideally suited to routine calibration work on four terminal resistance standards.

The CCC itself is tested to be accurate to 1 part in 10⁹ and using the optically isolated current sources the bridge can make comparisons between resistors with an accuracy and repeatability of better than 10^-8.  It is also possible to transfer the QHR standard to a temperature stabilised 100ohm resistor as a primary standard of resistance.