Pressure Transducers

Pressure is an important physical quantity to be measured in industrial systems.  

Transducers are one of the popular means of measuring Pressure.   Pressure Transducers work by converting the pressure signal into an analog electric signal usually a 4...20 mA signal. 

Pressure Transducers can be designed using many principles.  The most widely used of these are the capacitive and the Piezo-resistive transducer. 

Capacitive Pressure Transducers
The capacitive transducer consists of a diaphragm which works as one of the plates of a capacitor.  A fixed conductive surface acts as the other plate.  The permittivity of the space in between these plates varies as the diaphragm moves in response to the measured pressure. 

This change in capacitance is measured as the process pressure.  

The capacitive transducer is used to measure very low pressure values.  Very Accurate measurements are possible using the capacitive pressure Transducers. 

Piezo Resistive Pressure Transducers
Piezo Resistive Transducers work on the principle of the piezoresistive effect.  The piezo resistive effect refers to the change in the resistivity of a material in response to force or pressure.  The piezo resistive sensor is used widely in biomedical applications as well as in the automobile industry. 

Piezo Resistive Pressure Transducers
These sensors are low in cost and have high sensitivity.  They can be manufactured for a wide range of pressure measurement.

Piezo Resistive Pressure transducers consist of a diaphragm which is made of silicon.  The diaphragm bends due to the pressure of the system to be measured. 

Mounted on the diaphragm are four piezo-resistors which are usually arranged in the form of a Wheatstone bridge.  When the diaphragm bends due to the pressure, the piezoresistors are subject to either tensile or compressive stress.  This results in a change in resistance values which is measured through the Wheatstone bridge formation and is scaled as a pressure measurement