HIGH-PRECISION AC-DC TRANSFER STANDARDS AT ETL

A new measurement system has been developed in order to re-evaluate the present ac-dc transfer standards of the Electrotechnical Laboratory (ETL). The new measurement system consists of a high-precision comparator system and a modified fast-reversed dc source. The ac-dc transfer differences of thermal transfer standards were intercompared using the comparator system with a resolution better than 1 ppm. The absolute ad-dc transfer differences of single-junction thermal converters (SJTC's) were evaluated in terms of a multijunction thermal converter and by the modified fast-reversed dc method. The results obtained by the two methods agreed within 1 ppm.