FINITE-ELEMENT CALCULATIONS ON THE BEHAVIOR OF A DSC IN TEMPERATURE-MODULATED MODE

The influence of changes of sample properties on the amplitude and pha se shift of the differential-temperature signal as well as the influen ce of frequency changes has been calculated for a one-dimensional mode l of a temperature-modulated DSC (TMDSC) using a computer program for finite-element-method (FEM) calculations. Amplitude and phase shift of the measured signal Delta T (which is proportional to the differentia l heat-flow rate) is strongly influenced by the heat capacity of the s ample. The connection is only linear for rather small heat capacities. The influence of the heat-transfer coefficient between sample and sam ple pan on amplitude and phase shift of the signal is not so large and Linear (within the framework of our calculations). The influence of t he heat-transfer coefficient between sample and sample pan on amplitud e and phase shift of the signal is not so large and linear (within the framework of our calculations). For precise measurements, a very care ful ''calibration'' is needed, which must take all the aforementioned influences into account. (C) 1998 Elsevier Science B.V.