Meaning
Standard calibration practices define the method for determining the heat flow calibration of differential scanning calorimeters. Applying the astm e968 procedure ensures that the heat capacity and enthalpy measurements obtained during testing are accurate. It allows material testing laboratories to quantify energy changes during thermal transitions.
Calorimetric Accuracy
Differential scanning calorimetry relies on accurate measurement of the energy absorbed or released by a sample. Through the astm e968 calibration, the raw electrical signals generated by the instrument are converted into accurate units of heat flow or milliwatts. This calibration factor accounts for the thermal resistance of the sensor assembly.
Regular adjustments prevent drift in the heat flow measurements over time.
Reference Standard
Accurate heat flow measurements depend on reference materials with certified specific heat capacity or heat of fusion. Under the astm e968 protocol, high purity synthetic sapphire or high purity metals are measured against known literature values. These standards must be carefully handled to avoid surface contamination that would alter their mass.
Small changes in mass will introduce errors into the calculated calibration factor, which compromises subsequent measurements.
Calibration Limit
Thermal analyzer responses vary depending on the temperature range and the purging gas used. The astm e968 practice must be performed under the same environmental conditions and gas flow rates that are planned for the actual sample runs. Changes in the purge gas can alter the thermal conductivity of the sample chamber.
Consequently, different gas environments require individual calibration coefficients.
