Metrological Precision
The preservation of a constant ratio between relative change in electrical resistance and applied mechanical strain during long term operation defines the reliability of a sensor. For sensors deployed in high temperature environments, gauge factor stability determines the accuracy of stress and load calculations over time. Fluctuations in this ratio lead to calibration drift and introduce uncertainty in strain measurement.
Drift Driver
Structural changes in the sensing material represent the primary cause of variation in this ratio. Recrystallization and oxidation in thin film alloys alter the electronic transport properties of the film. These changes reduce the gauge factor stability of the sensor during sustained operation at high temperatures.
Thermal Stabilization
Thermal annealing is used to stabilize the microstructure of the sputtered film before calibration and field deployment. Heating the sensor to a temperature above its intended operating limit allows the film to complete its structural transition and relieve internal stress. This process ensures that the electronic properties remain constant during subsequent thermal cycles.
Verification Protocol
Calibration testing validates the constancy of the strain sensitivity by cycling the sensor through a known range of mechanical load and temperature. The sensor response is compared to a reference standard under controlled laboratory conditions to verify compliance with specified tolerances. This testing is performed after initial fabrication and after periodic intervals during service life to track the behavior of the device.
High precision calibration rigs are used to apply precise mechanical deflection while maintaining a constant temperature, allowing developers to detect even minor changes in sensitivity.
