An automated AC-DC transfer calibration system

Improvements in the National Research Council of Canada (NRC)'s ac-dc transfer capabilities have been achieved through full automation of the ac-dc transfer comparator, extensive redesign of the control software, and modification of the voltage buildup procedure. Hardware additions to the comparator design include stepping motor-driven switches and a range changer of a commercial electronic transfer standard. Redesigned software can be easily modified to accept new instruments and new procedures. The NRC voltage buildup procedure has been modified at the 500- and 1000-V levels. The expanded uncertainty assigned to the NRC working standard is given, and its components are briefly discussed.