Calibrating DSC Temperature

Temperature calibration is based on a run in which a temperature standard (e.g., indium) is heated through its melting transition using the same conditions to be used in subsequent measures (e.g., heating rate and purge gas). The recorded melting point of this standard is compared to the known melting point and the difference is calculated for temperature calibration. Up to five standards may be used for temperature calibration. A single-point calibration shifts the sample temperature by a constant amount. A two- or more-point calibration shifts the temperature by a constant amount below the first point, uses a smooth curve through the calibration points and shifts by a constant amount after the last point.

During cell constant calibration, the temperature calibration data from the cell constant calibration experiment is automatically stored when the cell constant calibration results are saved.

NOTE: A multiple-point calibration is more accurate than a one-point calibration. A single-point calibration shifts the sample temperature by a constant amount. A two- or more-point calibration shifts the temperature by a constant amount below the first point, uses a smooth curve through the calibration points and maintains a constant temperature shift after the last point.

A general procedure for temperature calibration is given below:

Choose an appropriate calibration material with a known melting point.
Prepare approximately 1 to 5 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. (In the calibration mode the current temperature table data is ignored.)
Select the "Temperature" 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.

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. Select Open File on the Calibration window and then select the DSC temperature data file created above.
Select the appropriate calibration type as specified by the test procedure, if incorrect, and analyze the data. See 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 temperature parameters with this calibration data.

You can verify this result by selecting Cell/Temperature Table from the Calibrate menu, then clicking on the Temperature Table tab.

Calibrating DSC Temperature

Calibrating DSC Temperature