Submillimetre thermistors for balloon‐borne applications up to lower stratosphere: preliminary characterization with 0.02 K uncertainty

Abstract

ABSTRACTThe French metrological laboratory LNE‐CNAM, in the framework of a study commissioned by the Laboratory of Dynamic Meteorology LMD, has carried out a preliminary metrological characterization of a device based on submillimetre thermistors, to be used for atmospheric temperature and humidity measurements from the ground up to the lower stratosphere.The device is a measuring system intended to perform temperature measurements between 173 K (around ‐100 °C) and 233 K (around −40 °C). It is composed of a self‐manufactured electronic device, in which submillimetre thermistors measure both air temperature and the temperature of a hygrometer sensor, in order to determine accurately water vapour concentration. Since the needed final measurement uncertainty is below 0.05 K, a comprehensive metrological characterization must be performed.One instrument prototype was supplied to the LNE‐CNAM, to be characterized between 173 K and 273 K (around 0 °C). Measurements were carried out in the quasi‐adiabatic calorimeter used by the LNE‐CNAM to realize the national temperature standard below 84 K. The calorimeter was adapted to work at temperatures up to 273 K. At any setpoint between 173 K and 273 K, the stability of the temperature was within 5 mK for several hours. The thermistors were calibrated by comparison to a calibrated reference thermometer.Preliminary results showed that calibrations with an uncertainty of around 0.02 K are possible. Tests are going to be performed in situ by the LMD, and further characterizations will be carried out to assess the obtained uncertainties and check long‐term reproducibility.