The core function of a differential scanning calorimeter (DSC) is to measure the thermal effects that occur during the programmed temperature control process of a sample. The essence of its working principle is dynamic heat flux compensation and precise measurement, ultimately achieving quantification of key thermodynamic parameters such as enthalpy change, melting point, and glass transition temperature.

1、 Core Design: Symmetry and Differential Measurement

The core component of DSC is a precision furnace with two independent measurement platforms inside: one for placing the measured sample (S), and the other for placing inert reference materials (such as empty crucibles or alumina powder). These two platforms are closely connected through a heat flow sensor, forming a symmetrical measurement system. This differential design aims to eliminate background thermal interference and only measure the thermal effects of the sample itself.

2、 Working process: dynamic compensation of heat flux difference

Throughout the entire experimental process (such as heating, cooling, or constant temperature), the instrument control system is always committed to maintaining the temperature consistency between the sample end and the reference end. When a sample undergoes physical or chemical changes (such as melting and heat absorption or crystallization and heat release), it absorbs or releases heat, attempting to make its temperature lower or higher than the reference end.

At this point, the detection system of DSC will immediately detect this small temperature difference (in power compensated DSC) and quickly compensate the corresponding electrical energy to the sample or reference end, restoring the temperature balance at both ends. The compensation power required to maintain temperature balance (unit: milliwatts, mW) is directly equal to the rate at which the sample absorbs or releases heat flux. Therefore, the vertical axis signal of the instrument is directly recorded as the heat flow rate (HeatFlow).

3、 Data interpretation: from heat flow curve to enthalpy change calculation

Finally, we obtain a curve of heat flux as a function of temperature or time. The peak (endothermic) or valley (exothermic) on the curve represents the thermal event of the sample.

The calculation of enthalpy change (Δ H) is based on this curve: the total heat absorbed or released by a thermal event is equal to the integral of its peak area over time. The calculation formula can be simplified as Δ H=K × A/m, where:

A is the area of the peak.

M is the quality of the sample.

K is the instrument constant (sensitivity coefficient), which is calibrated by measuring a standard substance (such as indium) with a known melting enthalpy.

In summary, DSC utilizes sophisticated differential design to convert subtle thermal changes in the sample into measurable electrical signals (heat flux difference), and ultimately converts the dynamic heat flux curve into quantitative enthalpy change data through integration calculation, thereby revealing the intrinsic thermal properties of the material.