The thesis addresses the determination of the thermal conductivity coefficient
of various samples by temperature measurement inside a temperature controlled
chamber. It also focuses on the comparison of four IMS circuits with different
thermal conductivity coeffients, based on heat flow analysis. First, the production
of temperature controlled chamber is described. The description consists of all
the components of the system. It also describes all the electric circuits, measuring
the electrical and thermal quantities. The core of this paper describes the basic
program flowchart of the micro-controller and the problem with analogue-todigital
conversion of the temperature measurement. High switching frequency of
MOSFET transistors in a H-bridge turns out to be very problematic, causing large
disturbances in the temperature measurement. It also has a significant impact
on the temperature control. In order to minimize the disturbances, a new way
of triggering the analogue-to-digital converter of a temperature measurement is
proposed. Rather than PID, PI controller is used due to its smaller disturbance
sensitivity. At the end of this paper, the results of thermal conductivity coefficient
measurement of different materials via absolute technique are presented. Heat
losses and the cooling ability of four IMS circuits is also analysed. Heat loss
determination based on required cooling power of the IMS circuits cannot be
confirmed as credible.
|
