Is a piezoelectric transducer a passive device

Piezoelectric converter

Definition: The piezoelectric transducer is a electroacoustic transducer use for conversion of print or mechanical stress in a change electric power. It is used to measure the physical quantity such as force, pressure, load, etc., which cannot be measured directly.

The piezo converter converts the physical quantity into an electrical voltage that can be easily measured with analog and digital measuring devices.

The piezoelectric transducer uses the piezoelectric material which has a special property, i.e. H. the material induces stress when the pressure or stress is applied. The material exhibiting such a property is known as an electro-resistive element.

The word piezoelectric means the electricity produced by pressure. Quartz is the examples of natural piezoelectric crystals, whereas Rochelle salts, ammonium dehydration, phosphate, lithium sulfate and dipotassium tartrate are examples of artificial crystals. The ceramic material is also used for piezoelectric transducers.

The ceramic material has no piezoelectric property. The property is then developed through a special polarization treatment. The ceramic material has several advantages. It is available in different shapes and sizes. The material has the ability to work at low voltages and it can operate at temperatures in excess of 3000 ° C

Piezoelectric effect

The EMF evolves due to the shift in fees. The effect is changeable, i. H. When the varying potential applies to a piezoelectric transducer, it changes the dimension of the material or deforms it. This effect is known as the piezoelectric effect.

The pressure is exerted on the crystals with the aid of the force summation devices, for example, the load is applied by mechanical manometers and pressure sensors, etc. The deformation induces the emf which determines the amount of pressure applied.

Theory of the piezoelectric transducer

A piezoelectric crystal is shown in the following figure.

The polarity of the charge depends on the direction of the applied forces.

Where, d - charge sensitivity of the crystals
F - applied force in Newtons

The force changes the thickness of the crystals.

Where A - area of ​​the crystals in square meters
t - the thickness of the crystals in meters
E - Young modulus N / m2

The young module is

where ω - width of the crystals in meters
l - the length of the crystals in meters

If we plug the value of the force into the charge equation, we get

The output voltage is obtained based on the electrode charges.

G is the voltage sensitivity of the crystals.

Where E0 - electric field strength, V / m

The voltage sensitivity of the crystals is expressed by the ratio of the electric field strength and the pressure.

When the mechanical deformation occurs in the crystals, charges are generated. And this charge develops the voltages across the electrodes.

The piezoelectric crystal is sensitive to direction. The polarity of the tension depends on the direction of the force, which is either pull or compression. The size and polarity of the charges depend on the size and direction of the applied force.

Operating modes of the piezoelectric crystal

The piezoelectric crystals are used in many modes such as thickness shear, face shear, thickness extension, transverse extension, etc. The illustration of the fear scissors is shown in the figure below.

Properties of Piezo Electric-Crystal

The properties of the piezoelectric crystals are listed below.

  1. The piezoelectric material has a high stability.
  2. It is available in different shapes and sizes.
  3. The piezoelectric material is insensitive to temperature and humidity.

Use of piezoelectric crystal

The piezoelectric transducers are used in the following.

  1. The piezoelectric material has a high stability and is therefore used to stabilize the electronic oscillator.
  2. The ultrasonic generators use the piezoelectric material. This generator is used in SONAR for underwater detection and in industrial cleaning equipment.
  3. It is used in microphones and speakers to convert the electrical signal into sound.
  4. The piezoelectric material is used in electric lighters.

The converter has a low output and therefore an external circuit is connected to it.