Piezoresistive pressure sensor.

Pressure sensors are designed to produce an output voltage or current that is dependent on the amount of pressure being sensed. Piezoresistive sensors are very popular because of their small size, reliability, and accuracy . These sensors are available in ranges from 0–1 psi (pounds per square inch) and 0–30 psi. The sensing element is a silicon diaphragm integrated with an integrated circuit chip. The chip contains four implanted piezoresistors connected to    form a bridge circuit . When pressure is applied to the diaphragm, the resistance of piezoresistors changes proportionally to the applied pressure, which changes the balance of the bridge. The voltage across V0 changes in proportion to the applied pressure (V0 V4 V2 [when referenced to V3]). Typical millivolt outputs and pressures are shown below:
1 psi 44 mV
5 psi 115 mV
15 psi 225 mV
30 psi 315 mV   

       

Piezoresistive bridge.

 

Piezoresistive pressure sensor. (Courtesy
Honeywell’s Micro Switch Division.)