Analysis of calorimetry measurements

A differential scanning calorimeter operable to obtain a thermogram from a sample, comprising:

• a sample cell,
• a reference cell,
• a thermal shield disposed around the sample cell and the reference cell,
• a cell heater arranged to heat the sample cell and the reference cell,
• a thermal sensor arranged to measure a difference in temperature between the sample cell and the reference cell, and
• a processing system configured to control the cell heater and receive temperature measurements from the sample cell and reference cell, and to determine a first thermogram comprising estimates of heat capacity at each of a range of temperatures for a test substance in the sample cell, the estimates being responsive to a difference in the amount of heat required to maintain the sample cell and reference cell at the same temperature while the temperature of both the sample cell and reference cell is varied,
• wherein the processing system comprises a memory for storing a second thermogram, and the processing system is configured to compare the first thermogram with the second thermogram, by:
• determining a smoothed first thermogram and a smoothed second thermogram by respectively performing a smoothing operation on the first thermogram and the second thermogram;
• determining a processed first thermogram and a processed second thermogram by respectively finding a derivative of the smoothed first thermogram and the smoothed second thermogram;
• determining the degree of similarity from a correlation operation comparing the processed first thermogram with the processed second thermogram.