Piezoelectric Transducer

Principle and Design 

Piezoelectric pressure transducers depend on the principle of ‘piezoelectric effect’ i.e., when some pressure or stress is applied to the surface of the piezoelectric crystal, an electric charge voltage will be developed by the crystal. The materials used in the construction of piezoelectric crystals are quartz, Rochelle salt, dipotassium titrate, lithium sulphate, barium titanate etc.
A piezoelectric pressure transducer is formed by connecting a diaphragm to the piezoelectric crystals and this assembly is shown below.  

 Working 

The pressure which is to be measured is applied to corrugated metal diaphragm. The diaphragm deflects depending on the applied pressure, and this deflection signal is transmitted to the crystal through the
mechanical link. In other words, the pressure is applied to the crystal through the diaphragm and the link.
When the crystal senses the pressure it will generate some voltage corresponding to the applied pressure, and is measured in the output voltage measuring device which is calibrated in terms of applied pressure. 

Applications 

 (a) These can be used in the process which requires measurement of high pressure.

(b) Can be applied in those systems which requires measured variable in electrical form.

Merits

1. Provides electrical output.
2. This transducer does not require any external power supply.
3. Size in small.
4. Rugged construction.

Demerits

1. It cannot be used for static pressure measurements.
2. The response will get affected by the variations in temperature.
3. In some cases it requires signal conditioning circuitry which is complex.
4. Cost is high.