Silicon Pressure Cell Fill Oil Volume Verification Methods
Confirm fill oil volume using pre- and post-injection micro-gravimetric mass checks combined with non-contact laser interferometric diaphragm dome profiling.
Silicone Fill Oil
Fluid Standard
High-purity synthetic polymer liquid acts as the primary force transmission medium in isolated-diaphragm pressure sensors. In these instruments, silicone fill oil transfers process-line pressure changes from the thin metallic outer diaphragm to the internal sensing chip. This liquid must exhibit low compressibility and a high boiling point to ensure stable measurement transmission under varying pressure loads, which protects the delicate silicon transducer from direct contact with corrosive process fluids.
Viscosity Behavior
Liquid flow resistance changes with temperature, which directly impacts the response speed of the pressure transducer. The selection of silicone fill oil relies on a low temperature-viscosity coefficient to maintain fast response times in cold climates. High-viscosity fluids are avoided in dynamic applications because they introduce measurement lag and dampen fast pressure pulsations.
Dielectric Property
Electrical isolation is necessary to prevent ground loops and short-circuits between the metal diaphragm and the silicon sensing element. Using silicone fill oil provides high dielectric strength, which protects the sensitive micro-machined bridge from external electrical surges. This isolation is verified during production through high-voltage insulation tests.
Chemical Stability
Thermal decomposition or chemical breakdown of the oil creates gases that destroy sensor calibration. Standard silicone fill oil withstands continuous high temperatures without outgassing or polymerizing. This stability ensures a long operating life for the sensor in industrial process plants.