The measurement method of the fully automatic micro saturation vapor pressure analyzer is based on the principle of thermodynamic equilibrium. The saturation vapor pressure is obtained by controlling the temperature and measuring the relationship between liquid vapor pressure and temperature. The core steps include sample preparation, parameter setting, sample injection, sealing testing, data acquisition and processing, as follows:
Sample preparation: Prepare the liquid sample to be tested according to the testing requirements, ensuring that the sample is pure and free of impurities, and avoiding the influence of impurities on the measurement results. Usually, a fully automatic micro saturation vapor pressure analyzer only requires a small amount of sample, such as 3ml, to complete the test.
Parameter setting: Set instrument parameters based on sample properties and testing standards. The fully automatic micro saturation vapor pressure analyzer usually uses a fixed sample volume for testing at a constant temperature, such as 37.8 ℃± 0.1 ℃. Meanwhile, the instrument may support selecting pressure units (such as kPa or psi) to meet different testing requirements.
Sample injection: Inject the liquid sample to be tested into the testing chamber of the instrument through the diaphragm, taking care not to exceed the maximum scale line. Some instruments, such as the DCWBH-A02 fully automatic micro saturation vapor pressure tester, use a 15ml testing chamber to ensure the compatibility between the sample and the testing chamber.
Sealing test: Ensure that the testing chamber is well sealed to prevent leakage. Fully automatic trace saturation vapor pressure analyzers usually have automatic sealing function to reduce errors caused by manual operation.
Data collection and processing:
Temperature control: The instrument precisely adjusts the sample temperature through a built-in temperature control system, ensuring temperature stability of ± 0.1 ℃ or higher accuracy.
Vapor equilibrium: At a set temperature, liquid molecules gradually evaporate to form vapor, which forms a closed space with the air above. As the temperature stabilizes, the volatile components in the sample continuously evaporate and mix with air to reach dynamic equilibrium. At this point, the pressure inside the container is the saturated vapor pressure.
Pressure measurement: The instrument uses high-precision pressure sensors (with a resolution of up to 0.01kPa or 0.1kPa) to monitor the gas pressure inside the test chamber in real time. Measure a pressure value every minute until the difference between the three measured values is within 0.1kPa, at which point the pressure value is the final result.
Result output: The instrument automatically calculates and outputs the saturated vapor pressure value. The test results can be displayed as total vapor pressure (Ptot), dry Reid vapor pressure value (DVPE), EPA vapor pressure value, etc., meeting the requirements of different testing standards.
During the measurement process, the following points should also be noted:
Standard compliance: The measurement method of the fully automatic micro saturation vapor pressure analyzer usually follows international standards such as GB/T8017, ASTMD323, etc., to ensure the accuracy and reliability of the test results.
Operating standards: Strictly follow the instrument manual to avoid erroneous operation that may cause distortion of test results. For example, during the sample injection process, it is necessary to ensure that the sample is pure and free of impurities; During the sealing test, it is important to ensure that the testing chamber is well sealed.
Instrument maintenance: Regularly maintain the instrument, such as cleaning the testing chamber, checking the pressure sensor, etc., to ensure that the instrument is in good working condition. At the same time, calibrate the pressure sensor monthly using standard substances such as n-heptane to ensure measurement accuracy.