To measure the the glass transition temperature using DSC, the point of inflection of the heatflow thermogram is usually taken as glass transition temperature. This can also be obtained by taking first derivative of DSC thermogram in which a peak is ovserved corresponding to the point of inflection of the heatflow thermogram.

Please check this RG discussion: https://www.researchgate.net/post/Can_we_find_glass_transition_temperature_from_heat_capacity_vs_temperature_curve

The best method to select may depedn on what kind of glass you want to study: polymer glass or silicate glass maybe metallic glass? In the case of polymers I woudl suggest either DSC or DMA (dynamic mechanical analysis). Be aware of the fact the the actual values depends on the method, as Tg is not thermodynamic transition, rather a kinetic one depending on the measuring frequency (or heating rate)

Old classical method was to analyze viscosity -- temperature dependencies.

Hi

If you could send the DSC thermogram it could be possible to tell. in most of the causes the Tg will give a small jump in the DSC curve. so better send the graph.