Oil Cavity Volumetric Expansion Mitigation in Piezoresistive Transducers
Minimizing fluid volume below five microliters and matching diaphragm spring rate eliminates thermal zero shift in isolated piezoresistive pressure cells.
Low-Stiffness Corrugation
Flexible Geometry
The formation of concentric ridges on a metal diaphragm increases its flexibility and reduces the force required to deform it. Utilizing low-stiffness corrugation allows the diaphragm to bend easily under low pressures without creating a large reaction force. This design is essential for measuring very low differential pressures.
Mechanical Sensitivity
A flat metal sheet of the same thickness would be much stiffer, requiring more pressure to achieve the same displacement. By reducing the stiffness, the sensor becomes highly sensitive to small pressure changes, which improves the resolution of the instrument. This sensitivity is particularly valuable in draft range and flow rate measurements.
Thermal Drift Reduction
When the internal fill fluid expands due to temperature changes, a stiff diaphragm would resist this expansion, causing a large pressure buildup and zero shift. The corrugated design allows the diaphragm to accommodate this thermal expansion with minimal resistance, thereby reducing the temperature-induced error. This reduction ensures the sensor maintains its baseline accuracy in fluctuating environments, and it prevents the internal electronics from seeing a false pressure increase that would distort the measurements.
Structural Limits
While the corrugations increase flexibility, they must be designed to withstand high static pressures without permanently deforming. If the diaphragm is over-stretched, the corrugations will lose their shape, permanently changing the calibration of the sensor. Manufacturers use finite element analysis to optimize the ridge profile, balancing high sensitivity with robust overpressure protection.