High resolution temperature measurement technique for materials sciences experiments in space

In order to perform crystal growth experiments under microgravity it is necessary to measure the temperature of material samples with high accuracy. The very small signal amplitude and the difficult electromagnetic conditions in the melt furnace require an electronic system of outstanding performance. The limits of the attainable accuracy, noise immunity and on-line data access made necessary a new device concept. Based on first experiences on MIR’92, the electronic measurement system TEGRA (TEmperature and GRAvitation data) was developed and used successfully in the EUROMIR’95 and MIR’97 missions. It was designed to measure temperatures of up to 10 thermocouples (NiCr–NiAl or Pt–PtRh) with a resolution down to 2.5 mK. The concept includes differential thermometry and other applications whenever a high accuracy measurement of slowly drifting signals is required in an electromagnetically contaminated environment. Furthermore, a large microgravity database has been collected.