Null Output Instability
A gradual and unintended shift in the zero pressure signal occurs in sensors using silicon strain gauges. Piezoresistive offset wander complicates the measurement of low pressures where the error might represent a large portion of the total signal. The phenomenon is often distinct from thermal drift because it can occur at a constant temperature.
Root Cause Analysis
Moisture absorption into the protective gels or the sensor housing is a common driver of this instability. Ingress of water molecules alters the dielectric properties and applies parasitic stresses to the piezoresistive offset wander sensitive bridge. Chemical contamination or the slow outgassing of adhesives can also cause the baseline to move.
Verification Protocol
Testing involves monitoring the sensor output over several days while keeping the pressure at zero. A stable piezoresistive offset wander profile indicates that the internal components have reached mechanical equilibrium. If the output continues to move after a long stabilization period, the device may be unsuitable for precision applications.
Calibration Boundary
Electronic compensation can correct for a known shift, but unpredictable movement is difficult to manage. Excessive piezoresistive offset wander often signals a failure in the chip passivation. Maintaining a stable zero point is essential for accuracy.
