Isolated Silicon Pressure Cell Oil Dosing Volume Tolerances and Temperature Hysteresis
Isolated silicon cell thermal hysteresis depends directly on micro-dosing oil volume accuracy and outer diaphragm compliance balance.
Mechanical Strain Hysteresis
Elastic Memory
Material properties cause a sensor to give different readings for the same input depending on whether the value was approached from above or below. This mechanical strain hysteresis is a form of lag in the elastic response of the diaphragm or housing. It represents the energy lost during a loading and unloading cycle.
The error is most pronounced at the midpoint of the measurement range.
Path Dependency
The internal structure of the metal or silicon retains a memory of its previous state. When mechanical strain hysteresis is present, the up-scale and down-scale calibration curves do not overlap. This separation is measured as a percentage of the full scale output.
Sensor Drift
Repeated cycling can cause the hysteresis loop to change shape over time. Minimizing mechanical strain hysteresis requires the use of high purity materials and specialized heat treatments. Sensors made from single crystal silicon show much less of this effect than those made from stainless steel.
Stabilization Time
Holding the sensor at a constant pressure for several minutes can reduce the impact of the lag. Because mechanical strain hysteresis is a physical property, it cannot be easily corrected by software. Technicians verify the level of hysteresis during a five point calibration sweep.