AC and DC shunts - can you believe their specs?

Little new information regarding high current shunts (greater than 100 A), especially ac shunts, has been published in the last 30 years to the authors knowledge. Since the advent of new measurement capabilities, sensors, and lower uncertainties, recent findings regarding the performance of ac and dc shunts are presented. The findings are significant for users and calibration laboratories. Errors due to current feed-point selection, ac/dc difference, frequency response, the proximity effects of ferromagnetic materials, and the effects of nearby conductors are discussed. Factors that must be included in the determination of measurement uncertainty are provided and discussed.