Calculating Dielectric Zero Shift in Capacitive Pressure Transmitters under Vacuum
Vacuum pull-down removes polarizable gas from capacitive pressure cells, causing a dielectric zero shift calculated via gas polarizability and gap geometry.
Total Mass Loss
Volatile Metric
Mass reduction in polymers and adhesives when exposed to high vacuum and heat is a key indicator of material stability. The parameter known as total mass loss measures the percentage of a specimen’s initial weight that is released as gas during thermal vacuum testing. This metric is used to evaluate materials for use in space and high-vacuum industrial applications.
Material Screening
Standardized testing procedures like ASTM E595 are used to determine this percentage for different materials. A high total mass loss indicates that the material releases a significant amount of volatile compounds, which can contaminate nearby surfaces. Materials with low mass loss are preferred for sensitive applications to avoid this contamination.
Testing Condition
Tests are typically conducted in a vacuum chamber at a temperature of one hundred and twenty-five degrees Celsius for twenty-four hours. The pressure is maintained below seven millipascals to simulate the harsh conditions of space. The weight of the specimen is measured before and after the test to calculate the percentage.
Operational Impact
High outgassing can lead to the condensation of volatile compounds on sensitive optical lenses and solar panels. This condensation reduces the efficiency and performance of these components, potentially causing mission failure. By ensuring a low total mass loss, engineers can prevent these issues and ensure the long-term reliability of the system.
Furthermore, the material characterization data obtained from these tests assists in the thermal modeling of the spacecraft, allowing for more accurate predictions of contamination risks throughout the vehicle lifecycle.