Temperature Control of a Scientific Instrument

Abstract: The aim of the present Master’s Thesis was to improve the temperature control of a calorimetric instrument called STIC (Several Temperatures Isothermal Calorimeter). Calorimetry is the science of measuring heat, heat production rate or heat capacity; the present instrument is an isothermal calorimeter used for the measurement of thermal power from different types of processes. In the instrument, four calorimeters are placed in a temperature gradient between a warm and a cold side, both of which are temperature controlled. In order to have an open and transparent control system, new PID controllers were implemented using Simulink and dSPACE. Experiments were carried out to see the effect of external temperature changes on the STIC measurement signals. A simulation model of the STIC was also developed in MATLAB. To decrease the effect of external temperature changes, a new feed forward control was added to the cooling side. To test and tune this controller, both simulations and experiments were done. The simulation result gave an improvement of about 55% compared to the situation without feed forward-, while the experiments gave a lower improvement of about 25%. To test a possible application of the STIC, an experiment with the setting of gypsum (plaster of Paris) was carried out.