Onset Temperature

The extrapolated onset-temperature (according to DIN EN ISO 11357-1:2010-03) is the designed intersection point of the extrapolated baseline and the inflectional tangent at the beginning of the melting or crystallization peak. The baseline and the inflectional tangent are determined from the temperature-dependent heat flow signal. In the case of pure and homogeneous materials, the onset-temperature can be indicated as melting temperature. In contrast to peak-temperature, the onset-temperature is less dependent on heating rate and sample mass. Furthermore onset-temperatures are usually used for temperature calibration of a DSC.

Heat flow and enthalpy diagramm. Onset temperature is marked as T onset. The dotted line represents crystallization, the continous line represents melting