Piezoresistive Diaphragm Decoupling via Anodic Glass Pedestal Mounts
Anodically bonded Borofloat glass pedestals isolate silicon piezoresistive diaphragms from packaging strain, reducing zero thermal shift below 0.02 percent span.
Pressure Sensor Hysteresis
Output Deviation
A maximum difference in sensor readings at a single pressure point occurs depending on whether the pressure was approached from a lower or higher value. This characteristic, known as pressure sensor hysteresis, represents a fundamental limit on the repeat accuracy of a pressure transducer. It appears as a loop in the calibration curve, with the ascending and descending data paths diverging.
The magnitude of this deviation is expressed as a percentage of the full-scale span.
Material Behavior
The phenomenon stems from the non-elastic deformation of the sensing diaphragm and the adhesive layers holding the strain gauges. When exposed to high pressure, the molecules within these materials do not return immediately to their original resting positions when the force is removed. This lag causes the sensor to report a slightly higher pressure on the downward stroke than on the upward stroke.
Systemic Source
Friction in mechanical linkages and the magnetic properties of inductive elements can also introduce this lag. High temperatures can exacerbate the effect by softening organic sealants or bonding agents used in the assembly. Minimizing the thickness of these adhesive layers reduces the mechanical lag.
Metrological Evaluation
Calibration laboratories measure this effect by performing a multi-point test sequence that moves from zero to full scale and back to zero. The maximum difference between the two sweeps at any point defines the hysteresis value. This test is repeated across the entire operating temperature range to verify the sensor’s long-term performance.