In a piezoresistive pressure sensor, the resistors are connected in a wheatstone bridge on a diaphragm. The strain caused on the diaphragm by the pressure causes a change in the resistances. The change in resistance is directly proportional to the change in pressure.
Parameters for piezo-resistive pressure sensors:
Operating pressure range: This is the range of pressure over which the sensor can safely operate and an output signal.
Maximum pressure or burst pressure: This is the maximum value of pressure that can be withstood by the sensor without damaging itself. If the applied pressure is more than this maximum pressure value, it might result in device failure or inaccurate signal output.
Offset: The deformation of the diaphragm due to applied pressure unbalances the wheatstone bridge. This along with the printing tolerances of the bridge’s resistors give a small output signal, even at no pressure. This is called offset
Span: The difference between the output signals at zero pressure and the highest pressure of the sensor is known as Span or Full Scale Span
Thermal zero shift: The offset variation in output signal due to temperature variation is called thermal zero shift
Thermal span shift: The variation in the sensitivity of the sensor due to temperature variation is called thermal span shift.
Repeatability: Repeatability is the difference of output signal of many pressure applications over time, when the measurements are repeated under the same conditions.
Accuracy: Accuracy of a sensor is the combination of Linearity, Hysteresis, and Repeatability. Accuracy is always positive.
