PIEZOELECTRIC TRANSDUCER
This is an electroacoustic transducer which is used for the conversion of pressure or stress into an electrical force, a transducer will convert one form of energy into another if we apply pressure or force to this transducer then it will convert the applied energy into electric voltage, this transducer can be used for measuring quantities like force, pressure, stress… which can’t be measured directly
The applied pressure or force is converted to electrical voltage and it can be easily measured by the analog and digital meter
PIEZOELECTRIC EFFECT
The heart of the transducer is the active element it does the conversion of the electrical energy to acoustic energy and vice versa, mostly the active element would be a polarized material some part of it is negatively charged and the other will be positively charged
The electrodes are attached to the both of its opposite faces and if an electric field is applied to the material and then the polarized molecule will be aligned to the electric field themselves and this alignment of the molecules will change the dimension of the material and this phenomenon is called as electrostriction a permanently polarized material such as quartz or barium titanate will produce an electrical field when the material changes its dimension as the result of the applied force and this is called the piezoelectric effect and the transducer which uses this effect is called the piezoelectric transducer.
PRINCIPLE OF PIEZOELECTRIC TRANSDUCER
There are three main modes of operation depending upon how the piezoelectric material is cut
TRANSVERSE EFFECT
The applied force is along the neutral axis ‘Y’ and the charges are generated perpendicular to the line of force and the amount of the charges will depend on the dimensions of the element
LONGITUDINAL EFFECT
The charge produced will be independent of the size and shape of the element and it will be proportional to the applied force, to increase the charge output we can use elements that are mechanically in series and electrically in parallel
SHEAR EFFECT
The produced charges will be proportional to the forces and it will be independent of the element’s size and shape and the charges for n elements will be
Cx = 2dxxFxn