Rebuilding of the Scales for ac-dc transfer at PTB with reduced uncertainties of measurement

Ac-dc transfer at PTB is performed using planar multijunction thermal converters. Scaling is used to calibrate standards for different voltage and current levels with calculable thermal converters on a quartz substrate as a reference. The number of steps in the scaling could be significantly reduced by exploiting the full dynamic range of the multijunction thermal converters which led to lower overall uncertainties. Applying ranges instead of single point values for the measurement values as well as for the frequencies drastically simplified the tables showing the best measurement capabilities.