Correlating Gas Leakage Rates to Fluid Ingress in Sensor Seals
Correlating gas leakage rates to liquid ingress requires deriving equivalent pore radius to confirm capillary entry pressure exceeds target hydrostatic head.
Contact Angle
Surface Energy
Geometric angles formed at the junction of a liquid, a gas, a vapor and a solid surface quantify the wettability of a substrate. This contact angle indicates whether a liquid will spread or form a bead on a component. Values below 90 degrees indicate high surface energy and good wetting, whereas values above this mark suggest a hydrophobic state.
Measurement Process
Optical goniometers measure this value by placing a controlled droplet of purified water onto the surface using a precision syringe. High-resolution cameras capture the profile of the drop. Analysis software then draws a tangent line at the point where the droplet edge meets the solid base.
Surface Behavior
Dynamic measurements involve expanding and contracting the volume of the drop to find the advancing and receding angles. The difference between these two values represents the hysteresis of the surface. A large gap between them often points to surface roughness or chemical heterogeneity.
Calibration Standard
Traceability in these measurements requires the use of certified reference surfaces with known energy levels. Environmental conditions like humidity and ambient temperature must be controlled because they influence the evaporation rate and liquid properties. Because organic vapors in the air can deposit on the test surface and change the result, measurements are conducted immediately after cleaning or surface treatment.
Regular verification against a known standard ensures the optical alignment and software algorithms remain within the specified tolerance.