Calibration of a RuOx Resistance Sensor
Utilized for Relaxation Calorimetry
under Magnetic Fields

The resistance thermometer are suitable for relaxation calorimetry due to their good temperature resolution and high accuracy. We have tried to calibrate the RuOx chip type resistance thermometer under magnetic fields by two different methods. In the first method, the RuOx thermometer was calibrated against the standard thermometer mounted on the mixing chamber surrounded by the cancellation coil. The RuOx thermometer shows negative magnetoresistance at the dilution temperature region. Using the calibrated sensor, we have succeeded in a blank measurement. In the other method, the RuOx thermometer is calibrated against the capacitance thermometer which shows no magnetic field dependence. The RuOx shows positive magnetoresistance at liquid helium temperature. However, their temperature dependences are affected by external magnetic fields.

(by S. Yamashita & Y. Nakazawa)

	Fig. 1. Temperature dependence of the magnetoresistance of a RuOx thermometer (KOA co. ltd.) in the dilution temperature region. The RuOx thermometer is calibrated against the standard thermometer mounted on the mixing chamber fixed inside the cancellation coil. The negative magnetoresistance is observable from the figure.
	Fig. 2. Temperature dependence of magnetoresistance of the RuOx thermometer. The RuOx thermometer is calibrated against the capacitance thermometer. The positive magnetoresistance is observable.