Transducer Substrate
Micro-machined semiconductor elements containing a thin diaphragm with integrated piezoresistive or capacitive sensors convert physical force into electrical signals. A silicon MEMS pressure cell utilizes these miniature structures to detect changes in gas or liquid pressure with high sensitivity. This cell is mounted inside a protective housing to isolate it from stressful mounting forces while allowing the media to contact the sensing surface.
Instrumentation engineers use these devices in automotive and industrial transmitters where space is limited.
Diaphragm Stress
Deflection measurements performed on the silicon microstructure determine the mechanical limits of the sensor under peak operating conditions. In a silicon MEMS pressure cell, the thickness of the etched diaphragm determines the full-scale pressure range and the overpressure limit. Finite element modeling helps designers optimize the placement of the sensing elements to maximize signal output while minimizing mechanical stress.
These designs are tested by applying cyclical pressure pulses to verify that the structure does not suffer from fatigue or hysteresis.
Thermal Sensitivity
Temperature changes introduce thermal stresses that can cause the output of the micro-machined sensor to drift away from its calibrated baseline. To correct for this behavior, a silicon MEMS pressure cell is tested across its full operating temperature range in a specialized environmental chamber. The resulting temperature-compensation coefficients are programmed into an adjacent digital signal processor to adjust the output in real time.
Metrologists use stable pressure controllers to apply reference pressures at each temperature step, ensuring that the sensor meets its specified thermal accuracy limits. Without this compensation, the temperature coefficient of offset would exceed the limits allowed for precision industrial measurements.
Calibration Verification
Reference standards maintained by the calibration laboratory are used to verify the measurement accuracy of the sensor before it is installed in the field. The output of the silicon MEMS pressure cell is compared directly against a high-precision deadweight tester at several points across the measurement span. These calibration records must be traceable to national standards to certify the measurement performance of the device.
Any unit that fails to meet the specified accuracy class is returned for re-characterization.
