Improved vacuum thermocouples

Prior construction of single junction vacuum thermal convertors (SJTCs) did not consistently produce units with AC-DC differences of a few ppm or less. Four improvement modes have been introduced. (1) Elimination of flaming during the making of the mounting bead. (2) Changing of the feed-through posts from Dumet to platinum-iridium. (3) Decrease of the Thomson coefficient by changing from nickel-chromium to Evanohm heater wire. (4) Lowering of the temperature gradient along the heater wire in the vicinity of the thermocouple. SJTCs can now be constructed with AC-DC differences of less than 0.3 ppm at a high yield.<>