Calibrating the Enthalpy (Cell) ConstantCalibrating the Enthalpy (Cell) Constant
This calibration is based on a run in which a standard metal (e.g., indium) is heated through its melting transition. The calculated heat of fusion is compared to the theoretical value. The cell constant is the ratio between these two values. The onset slope, or thermal resistance, is a measure of the suppression of temperature rise that occurs in a melting sample in relation to the thermocouple. Theoretically, a standard sample should melt at a constant heating rate. As it melts and draws more heat, a temperature difference develops between the sample and the sample thermocouple. The thermal resistance between these two points is calculated as the onset slope of the heat flow versus temperature curve on the front of the melting peak. The onset value is used for kinetic and purity calculations to correct for this thermal resistance.
The temperature calibration data from this experiment is automatically stored when the cell constant calibration results are saved.
DSC Q100 and Q1000 enthalpy calibration must be performed again after a Tzero calibration and any time the heat flow selection is changed.
Select from the following topics for more information:
This calibration experiment may be performed by setting up the experiment manually using the Experiment View or automatically using the calibration wizard.
A general procedure for enthalpy constant calibration is given below:
Choose an appropriate calibration material with a known heat (e.g., indium).
Prepare approximately 10 mg of the calibration material in a sample pan. Crimp the pan, then position it on the sample platform.
Prepare a reference pan using the same pan type used for the sample. Crimp the pan, then position it on the reference platform.
Cover the cell.
Check that your purge gas is connected and set to the desired flow rate. If you are using an RCS or LNCS, be sure a Base purge gas is also used.
Select Experiment View and access the Summary Page, then set the instrument to calibration mode using the Mode Selection drop-down list.
Select the "Cell Constant" test from the Test list.
Select the
calibration material from the Sample
Name list. Click on the 
button
and verify the calibration information for this standard. Enter
the requested sample information, including the exact Sample
Size.
Click on the Procedure tab. Enter the requested test parameters that will program the DSC to:
Equilibrate to a temperature below the onset of the literature melting temperature of the material. Use the following equation to determine that temperature:
5 min. X Heating Rate (°C/min) = Temperature (°C)
Typical example: 5 min X 20°C/min = 100°C (below the onset of the literature melting temperature)
Heat the material, at the same heating rate that you will use in your subsequent experiments, to 50°C above the literature melting temperature.
If you are using this standard for the first time, check the Premelt option to melt the sample before starting the experiment.
Click on the Notes tab. Enter/verify the requested information. If an MFC is installed, set the desired flow rate.
Click on the Apply button to save the experimental and sample parameters entered for this run.
If more than one run is in the sequence list, schedule this run. (An arrow will appear next to the run number in the Sequence Pane for the scheduled run.)
Select Start to begin the calibration run.
Wait until the run is complete, then access the calibration program using Calibrate/Analysis on the DSC menu. Once the run is complete, select Open File on the Calibration window and then select the DSC cell constant data file created above.
Select the appropriate calibration type, if incorrect, and analyze the data. See also: Analyzing DSC Calibration Data.
Save the calibration results by clicking the Accept button (or by selecting Analyze/Accept results from the calibration menu). This will update the current cell calibration parameters (cell constant and onset slope) and update the temperature table.
You can verify this result by viewing the Cell/Temperature Table window (selected from the Calibrate menu).
Q10 Calibration Wizard
Follow the steps below when using the calibration wizard with a DSC Q10:
Verify that the installed cooler type is selected on the Tools/Instrument Preferences/Cooler Page.
Select Calibration Wizard from the Calibrate menu.
Select Cell Constant/Temperature
option, then click Next.
For information on the next step click here 
more.
Q100/Q1000 Calibration Wizard
Follow the steps below when using the calibration wizard with a DSC Q100 or Q1000:
Select Calibration Wizard from the Calibrate menu.
Verify/select the installed cooling device and desired heat flow signal. Based on the heat flow selection the appropriate calibration wizard will be displayed.
Select the
Cell Constant/Temperature
calibration option, then click Next.
For information on the next step click here more.