A proposal for a multijunction thermal converter [AC-DC standard]

A multijunction thermal converter is proposed as an AC-DC transfer standard. It consists of a row of thermocouples composed of bismuth and antimony on a mica substrate and a twisted bifilar heater wire. The junctions of the thermocouples are alternately aligned in parallel lines on the substrate. The heater, made of a fine resistive wire, is placed on one line of the junctions to make the hot junctions of the thermocouples. A thick copper plate covered with a vinyl sheet is fixed on the other line of the junctions to make the cold junctions. The AC-DC transfer difference of the multijunction thermal converter was compared with that of a single-junction thermal converter. The measurements show that the AC-DC difference of the latter differs from that of the former by -3.3 p.p.m