MAGNETORESISTANCE OF A HIGHLY STABLE INDUSTRIAL-GRADE PLATINUM RESISTANCE THERMOMETER BETWEEN 20-K AND 240-K

The stability and magneto-resistance of a newly introduced Japanese Industrial Standard (JIS) platinum resistance thermometer were studied. The stability was estimated from the change in resistance at the triple point of water after thermal cycles between room temperature and liquid nitrogen temperature. The variation among the resistance values at 20, 50 and 100 cycles was < 1 mK. Its magneto-resistance was measured between 20 and 240 K under a magnetic field B of up to 8 t. The relative resistance increase, epsilon, was found to obey the equation epsilon = D(T)B2/[1 + E(T)B]. The fitting error in the field dependence was < 15 mK above 30 K and was about 0.1 % of the correction for a magnetic field of 8 T. The parameters D(T) and E(T) are tabulated for the new JIS thermometer and a standard rhodium - iron thermometer.