Multijunction thermal convertor. An accurate d.c./a.c. transfer instrument

The paper describes the performance and method of construction of a multijunction thermal convertor, which, it is claimed, should enable the r.m.s. values of alternating currents and voltages to be measured to an accuracy of within 1 part in 105, and probably 1 part in 106. The convertor gives a large output voltage and has a negligible d.c. reversal change and a short response time. The effect on its performance of Peltier and Thomson heating, and also the extent to which it integrates, have been considered. Equations have been developed to enable the reliability of the convertor as a d.c./a.c. transfer standard to be determined; the claims made for the accuracy of the convertor are based on the solutions to these equations.