Fast Synchronous Ac-Dc-Transfer with Thermal Converters

The most accurate measurements of the rms (root mean square) values of ac (alternating current) voltages are performed by means of thermal converters (TC) (Klonz, 2002) and digital sampling procedures (Ihlenfeld, 2001 and Ihlenfeld, et. al., 2003) (at low frequencies) with uncertainties of the order of some fractions of muV/V. The main drawback of using TCs relies on the long measuring times required, of a few minutes in most cases. In the following, a simple method for reducing the measuring time and to substantially speed up ac-dc transfer measurements will be described and documented with results of a comparison measurement