If a substance changes its state of aggregation or a solid changes its (crystal) structure during a temperature increase or decrease, this is called a phase transition.
In the simplest case, this is a melting or solidification. These processes can be well tracked with the DSC, since they always take place with energy absorption (endothermic) or with energy release (exothermic) in the form of temperature changes.
These temperature changes are measured by the DSC through one or more thermocouples (e) attached to the sample holder, which compares the exact sample temperature with the ambient temperature and a reference sample. From the difference between reference and sample, the exact energy value can be read off, the sign of the difference from the sample reference indicates whether an endothermic or exothermic process is present.
The location of the occurring effect when applied against the temperature also indicates very precisely when this takes place. The more accurate the measurement of the exact sample temperature, the better the resolution and sensitivity of the DSC.