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.
Diaphragm Compliance
Deflection Metric
Elastic deflection represents the volumetric change per unit pressure in a pressure-sensing capsule. When pressure is applied to a sensor, diaphragm compliance dictates how much oil is displaced into the internal sensor cavity. This parameter is measured in cubic millimetres per kilopascal.
A high value lowers the natural frequency of the sensor.
Metrological Impact
Sensing performance degrades when the temperature of the fill fluid fluctuates. Because fill fluid expands and contracts, diaphragm compliance must be high enough to absorb the volume shift without causing a massive zero shift. Manufacturers verify this behaviour during thermal cycling in controlled baths.
Calibration Factor
Instrument calibration requires compensation for the stiffness of the metal or ceramic sheet. While a thin metal disc yields high diaphragm compliance, it also increases susceptibility to overpressure damage. Engineers calculate the spring rate to balance sensor sensitivity against burst pressure limits.
This calibration is verified at the factory under reference conditions, where each sensor is subjected to stepped pressure sequences to record the baseline deflection.
Operating Boundary
System limits are defined by the temperature range over which the elastic response remains linear. Excessive pressure pushes diaphragm compliance into the plastic deformation region, which permanently ruins the sensor calibration.