Aspects of Application and Calibration of a Binary Compensation Unit for Cryogenic Current Comparator Setups

We have developed a binary compensation unit for balancing measurement bridges with cryogenic current comparators (CCCs) commonly used in resistance metrology. We present the basic design ideas for the new microcontroller-operated module. It offers balance over a gapless range of resistance ratios of the resistors to be compared. The binary setup allows for convenient calibration when being combined with a binary CCC. The calibration can be performed using the CCC´s control electronics and software. Examples of measurements demonstrate the unit´s high flexibility and stability of resistance calibration well below one part in 10⁹ over a period of 21 hours.