Thermal watt-transfer standard

A transportable ac power and energy standard developed at VNIIM is described. Based on a thermal principle, the instrument performs ac-dc transfer and absolute power and energy measurements in the frequency range from 40 to 500 Hz. The ac-dc transfer stability over a 3-month period is better than 10 ppm at a power factor of unity, and better than 30 ppm at a power factor of 0.5.<>