A temperature-controlled heat pipe standard resistor thermostat

Using the operation principle of the water heat pipe, temperature dampers were proposed to improve the temperature stability of standard resistors kept at 20 °C, resulting in the improvement of the accuracy of resistance measurements of platinum resistance thermometry by attenuating the effects of temperature fluctuations of the environment on the reference standard resistor temperature. A temperature-controlled heat pipe standard resistor thermostat using water as working fluid was successfully developed at the National Institute of Metrology (NIM). Also, the rugged stainless-steel container eliminates breaking of the water-in-glass heat pipe. We describe the design of the thermostat, the obtained results, and the effects of changes in room temperature on its performance. The results indicate that the temperature stability of the standard resistor within 13 hours was better than ± l mK when the heat pipe thermostat operating at 20 °C. Moreover, the changes in the environmental temperature can influence the performance of the heat pipe thermostat. A better stability of the room temperature improves the temperature stability of the standard resistor. Therefore, such thermostats are capable of meeting the requirements for accurate resistance measurements.