Tiêu đề 34. THERMAL ANALYSIS.pdf ✅

PHARMD GURU Page 4  The differential heat flow into the pans is directly proportional to the difference in the thermocouple signals.  The sample temperature is measured by the alumel/chromel thermocouple under the sample position.  This temperature is an estimated sample temperature because the thermocouple is not inserted into the sample itself.  The accuracy of this temperature will depend on the thermal conductivity of the sample and its container, the heating rate, and other factors.  The sample and reference pans both have lids and the reference pan is an empty pan. 2) POWER COMPENSATED DSC: FIG: POWER COMPENSATED DSC  The major difference in power compensated DSC instruments is that, two separate heating elements are used for the sample and the reference.  A change in temperature between the sample and the reference serves as the signal to “turn on” one of the heaters, so that the sample and the reference stay at the same temperature.  When a phase change, reaction, glass transition, or similar event occurs in the sample, the sample and reference temperatures become different.  This causes extra power to be directed to the cell at the lower temperature in order to heat it.