Presets
Playback
Sample and instrument
Both cells are controlled to follow the same ramp. When the sample melts it absorbs latent heat, so its heater must deliver more power than the reference heater; that difference is the DSC signal.
Model checks
The science
What is modelled
Two cells, each a heater block coupled through a contact conductance to a pan, are steered by a controller to follow a linear temperature ramp. The sample pan holds a material with sensible heat and a latent heat of fusion spread over a smooth melting range; the reference pan is empty. The signal is the difference of the two heater powers.
Equations
- Pan:
dH/dt = G (Theater - Tpan) - h (Tpan - Tamb), with the sample enthalpyH(T) = C(T - Tamb) + m L f(T)and a logistic melted fractionf(T). - Baseline step:
ΔP = m cp β(heating rate β in K/s). - Enthalpy of fusion:
∫ (ΔP - baseline) dt = m L.
Checks run in the page
- The baseline-corrected peak area against mass times latent heat.
- The same area at twice the heating rate.
- The pre-melting baseline against m c_p times the heating rate.
- The simulator's own energy bookkeeping residual.
Honest simplifications
The transition is a smooth logistic curve rather than a sharp first-order melt, the thermal lag of the instrument is a lumped conductance, and there is no thermal gradient inside the sample, no supercooling and no purge-gas effect. Not a calibrated analytical instrument.
What to try
- Press Fast ramp: the peak moves slightly up in temperature and gets taller, but the area under it is unchanged.
- Press Broad transition: the same latent heat is spread over a wider range, so the peak is lower and wider.
- Raise the mass and note that both the baseline step and the peak scale with it.