Long-term relative stability of thermistors: Part 2

The relative stability of four glass–bead thermistors has been analyzed for 66 months to determine if thermistors have sufficient relative stability to be used as feedback sensors for milliKelvin levels of temperature control. This paper provides additional drift data and new correlations beyond those described in a previous paper [Prec Eng, J Int Soc Prec Eng Nanotechnol 2001;25:24–8]. The thermistors were measured at 20±0.1 °C using commercial two-wire instrumentation. The thermistors have a nominal resistance of 12.5 kΩ and sensitivity of −4.5%/°C at 20 °C. They are nested together inside several layers of thermal resistance and capacitance which are held at nominal 20 °C with a heater controller that maintains the thermistor nest above the 19 °C ambient air temperature. After correction for instrumentation drift with two high-stability reference resistors, the average relative RMS drift of the thermistors is 48±16 μK, with an RMS fitted drift rate of 0.19±0.08 μK per week.