The synchronous thermal analyzer (STA) achieves multidimensional analysis of material thermal properties by synchronously measuring thermogravimetric (TG) and differential scanning calorimetry (DSC) signals. To ensure data reliability, regular critical maintenance and calibration are necessary, with a focus on optimizing temperature accuracy and sensitivity.
Key maintenance practices
Sensor cleaning and aging inspection
Thermocouple maintenance: After the experiment, wipe the surface of the thermocouple with a dust-free cloth to avoid signal attenuation caused by sample residue (such as oxides, polymers) covering it. Test the thermocouple response using standard melting point samples (such as indium and zinc) every quarter. If the melting point deviation exceeds ± 0.5 ℃, the thermocouple needs to be replaced.
Balance calibration: Calibrate the TG balance monthly using standard weights (such as 100mg, 500mg) to ensure weighing accuracy of ≤± 0.1%. If the environmental humidity is greater than 70%, the calibration frequency should be increased to once a week to prevent moisture adsorption from affecting weighing.
Maintenance of furnace body and atmosphere system
Furnace cleaning: Clean the accumulated dust in the furnace every six months, use a vacuum cleaner with a soft bristled brush to avoid scratching the heating elements. For high-temperature furnaces (>1000 ℃), it is necessary to check whether the thermocouple protective sleeve is cracked to prevent aluminum oxide powder from falling off and contaminating the sample.
Gas pipeline leak detection: Check the inlet, outlet, and sealing ring with soapy water every month to ensure no leaks. If inert gas (such as nitrogen) is used, flow stability should be monitored, and if the fluctuation exceeds ± 5%, the mass flow meter should be replaced.
Practice of Temperature and Sensitivity Calibration
temperature calibration
Multi point calibration method: Select 3-5 standard substances (such as indium, zinc, aluminum) to cover the instrument range (such as room temperature to 1500 ℃). Taking indium as an example, its melting point is 156.6 ℃. If the measured value deviation is greater than ± 0.3 ℃, the instrument temperature compensation coefficient needs to be adjusted.
Heating rate verification: Test the standard substance at commonly used rates such as 10 ℃/min and 20 ℃/min to ensure that the temperature hysteresis time is less than 5 seconds. Otherwise, optimize the PID parameters of the heating module.
Sensitivity calibration
DSC signal baseline correction: Collect baseline data during no-load operation. If there is linear drift (>± 5 μ V/min), the background signal needs to be subtracted through software; Nonlinear drift requires checking whether the thermocouple connection is loose.
Thermal flow signal calibration: Use a standard sample with known enthalpy (such as sapphire) to test its melting peak area under the same experimental conditions (such as nitrogen atmosphere, 10 ℃/min). If the measured value deviates from the theoretical value by more than ± 2%, the instrument gain coefficient needs to be adjusted.
summary
By regularly maintaining sensors, furnace bodies, and gas systems, and calibrating temperature and sensitivity using standard substances, the repeatability and accuracy of STA data can be significantly improved. Suggest establishing a calibration file to record the parameters and results of each calibration, providing a basis for long-term stability tracking of the instrument. For high-precision demand scenarios (such as pharmaceutical research and development), the calibration cycle can be shortened to once a month, and third-party metrology institutions can be introduced for traceability verification.