A reliability test of type R thermocouples as a reference standard

Type R thermocouples were exposed at the aluminum fixed point and 1100/spl deg/C atmosphere in order to estimate their E.M.F drift and inhomogeneity. A type R thermocouple, exposed at only aluminum fixed point, showed the increase of E.M.F. and inhomogeneity. On the other hand, another type R thermocouple, exposed at 1100/spl deg/C, showed the decrease and stability of E.M.F. and inhomogeneity. As for as the present results, it is not enough to anneal the type R thermocouples according to the JIS C 1602 conditions. It is cleared the further annealing is effective to stabilize the type R. thermocouples. A new theory, connected with the lattice vacancy and remained strain, is also successfully suggested in order to explain the behavior of type R thermocouple drift and inhomogeneity.