Transduction Geometry
Strain-gauge architecture translates mechanical boundary deflection into measurable electrical resistance changes through piezoresistive paths. A typical MEMS pressure sensor integrates a micromachined silicon diaphragm whose deflection alters under applied fluid force, changing the output voltage of an internal Wheatstone bridge. Piezoresistive elements diffuse directly into the active flexing region, converting physical strain into an analog signal without intermediate linkages.
Etched silicon thickness dictates the full-scale span, governing compliance before mechanical failure occurs at the rim anchors. Residual stress gradients across the diaphragm introduce baseline offsets during initial wafer release, requiring dry-etch compensation before packaging.
Calibration Drift
Thermal hysteresis shifts the zero-pressure output over repeated temperature cycles, demanding polynomial compensation tables stored in on-chip non-volatile memory. Package-induced mechanical stress transfers from the ceramic substrate or housing adhesive to the silicon die, generating span errors that outlast factory trimming. Long-term drift accumulates from silicon crystal relaxation and hermetic seal degradation, altering the internal reference vacuum of absolute types.
Diaphragm fatigue alters the elastic modulus over millions of pressure cycles, shifting the sensitivity slope away from the initial calibration curve.
Reference Standard
Traceability originates from primary dead-weight testers maintained by national metrology institutes, transferring pressure units down to secondary transfer standards. Manufacturers verify linearity against these pneumatic or hydraulic references at specific ambient temperatures, issuing calibration certificates that list hysteresis and repeatability errors. Static accuracy includes combined non-linearity, hysteresis, and non-repeatability expressed as a percentage of the full-scale output.
Factory acceptance testing subjects each production lot to thermal shock and proof pressure tests, discarding units whose offset exceeds predefined tolerance bands.
Overload Margin
Burst pressure ratings establish the physical safety boundary where structural rupture of the silicon diaphragm occurs, separating operational states from catastrophic failure. Overpressure limits define the maximum level a transducer withstands without suffering permanent calibration shift exceeding the stated tolerance class. Media compatibility restrictions prevent chemical attack on the exposed silicon or bond wires, limiting usage to dry gases or non-corrosive liquids unless protected by a gel isolation barrier.
Dynamic response speed depends on the internal cavity volume and media density, creating acoustic resonance limits that restrict high-frequency transient capture in closed hydraulic circuits.
