Working of Piezoelectric transducers and it's applications



A piezoelectric material is one in which an electric potential appear across certain surface of crystal, if the dimension of the crystal are change by application of a mechanical force. This potential is produced by displacement of charges. This effect is reversible, ie., if a varying potential is applied to proper axis of the crystal. It will change the dimension of crystal there by deforming it. This effect is known as Piezoelectric effect.

A basic structure of piezoelectric transducers is shown in the above picture. The crystal / piezoelectric element is sandwitched between two electrode plates. The voltage produced by the piezoelectric crystal is connected to amplifier for signal processing.

There are two categories of material that exhibits piezoelectric effect.

  1. Natural group: Element exhibits piezoelectric effect naturally.
    eg: quartz , Rochelle salt.

  2. Synthetic group: Man made crystal group from aquas solution.
    eg: Ammonium dihydrogen phosphate, Lithium phosphate, Lithium sulphate.

Piezoelectric effect is direction sensitive, that is a tensile force produces a voltage of one polarity, while a comprehensive force produces voltage of opposite polarity. Magnitude & polarity of induced surface charges are proportional to magnitude & direction of applied force.

Applications :

  • Used in Ultrasonic transducers

  • Pressure sensors

  • Accelometers

  • Gas igniters

  • Switces

Application of inverse transducers:

  • Actuators

  • Speakers and buzzers

  • Motors

Combination of both effects found in Active vibration control, Smart structure, Voltage transformer etc.,

Position and Motion Measurement