Discovery DSC™ Getting Started Guide
Page 52
Calibrating the Discovery DSC™
To obtain accurate experimental results, you should calibrate the Discovery DSC cell when you first install
it. For the best results, you should recalibrate periodically. The calibration procedures that you need to per-
form will vary depending on the heat flow selection. These experiments will be performed using the instru-
ment control software. For details on how to perform each calibration, refer to the online help accessed
through TRIOS software.
NOTE
: Please make sure that you run your experiments with the same gas that you used to calibrate the
system. For example, if you calibrate using nitrogen, make your runs with nitrogen.
Perform calibration runs that encompass the temperature range you plan to use in your experiments. We
recommend calibration over the widest temperature range; if your subsequent experiments cover a wider
range, you may wish to recalibrate.
For optimum experimental results, you will need to perform all DSC calibrations whenever you change
one of the following parameters:
•
First use of a new cell
•
Installation of new lid
•
Purge gas change
•
Cooling device or accessory change
Calibration consists of several different types of procedures that are described briefly below. For more
details on performing each type of calibration, refer to the instructions in online help.
T1 Baseline Calibration (Discovery DSC2500, DSC250, DSC25)
The baseline slope and offset calibration involves heating an empty cell through the entire temperature
range expected in subsequent experiments. The calibration program is used to calculate the slope and offset
values needed to flatten the baseline and zero the heat flow signal. Baseline Slope is a calibration constant
that accounts for the baseline slope of an empty cell. The baseline slope is calculated from data gathered as
an empty cell is heated through the temperature range expected in subsequent experiments. Default is 0.00.
Baseline Offset is a calibration factor that shifts the curve up or down along the Y-axis to balance the heat
flow at the sample and reference thermocouple positions. The baseline offset is calculated from data gath-
ered as an empty cell is heated through the temperature range expected in subsequent experiments.
Tzero
®
Calibration
The DSC Tzero calibration requires two experiments. The first experiment is done without samples or pans
(baseline); the second is performed with large (approximately 100 mg) sapphire disks (without pans) on
both the sample and reference positions. Both experiments use the same method, beginning with an equili-
bration at an initial temperature, holding isothermal for ten minutes, heating at constant rate to a final tem-
perature, and holding isothermal for ten minutes. The range of temperatures should be at least as broad as
the desired experimental range. Tzero calibration should be done at relatively high heating rates (such as
20°C/min) in order to obtain the most accurate calibration of the sensor thermal capacitance and resistance
values. Rates of less than 10°C/min are not recommended for Tzero calibration.
NOTE
: Tzero calibration is not available for the Discovery DSC25.
