Datum Definition
An empty volume devoid of all gas molecules establishes the absolute datum for pressure measurements. Transducers designed to measure absolute pressure rely on an internal chamber evacuated to this absolute zero pressure reference during the manufacturing process. The accuracy of this baseline dictates the sensor’s long-term performance under varying environmental conditions.
If the seal fails, the reference level shifts, which degrades the reliability of subsequent readings.
Physical Cavity
Evacuated chambers embedded in silicon microstructures represent the practical implementation of this datum. This sealed cavity prevents external atmospheric changes from altering the sensor’s baseline response. Silicon wafer bonding techniques create the physical boundary of the absolute zero pressure reference, securing the vacuum against gas permeation.
Thermal Influence
Thermal variations alter the residual gas pressure in the sealed volume. Even a minute leak or outgassing from internal surfaces raises the internal pressure, introducing measurement offset. To mitigate this, manufacturers use active getter materials to absorb liberated gas molecules.
Metrological Verification
High-precision calibration systems measure the sensor output against a known secondary standard. This test validates the sensor offset at the lower limit of its operating range. Stable absolute zero pressure reference performance is critical for industrial applications where barometric changes must be ignored.
