AC/DC Thermal Converters of the ETL

In order to establish alternating current and voltage standards, various types of thermal current and voltage converters have been constructed. From their detailed analysis, the specifications and characteristics have been determined. These converters have been used in a circular international comparison. A precise comparator of 0.1-ppm resolution has been also constructed. The estimated accuracy of current converters is better than 10 ppm up to 100 kHz and that of voltage converters is better than 25 ppm up to 50 kHz and 30 ppm at 100 kHz.