DEVELOPMENT OF THIN WIRE PLATINUM RESISTANCE THERMOMETER WITH ISOTROPIC MAGNETORESISTANCE

A thin wire platinum resistance thermometer with isotropic magnetoresistance is developed by adjusting the pitch angle theta(p) in the winding of the sensing wire to a specified 'magic' angle. The anisotropy between 20 and 70 K under magnetic fields of up to 8 T is smaller than 1%, compared with 35% for typical commercially available platinum resistance thermometers. The angular dependence of the magnetoresistance of the wire element used in the sensor is also measured between 6 and 40 K under magnetic fields of up to 8 T, to determine an optimized design of the sensor. A correction function with three temperature-independent fitting parameters is determined for the present sensors with an accuracy of 60 mK between 20 and 100 K under magnetic fields of up to 8 T.