The document discusses piezoelectric transducers. It explains that piezoelectric transducers use piezoelectric materials that generate a voltage when pressure or stress is applied. Piezoelectric transducers convert mechanical energy into electrical energy and are used to measure physical quantities like force, pressure, and stress. Common piezoelectric materials include quartz crystals and ceramic materials that are polarized to gain piezoelectric properties. When stress is applied, the ions in the material move and generate an electrical charge that can be measured.

1. PIEZOELECTRIC TRANSDUCER
E.KAROLINEKERSIN
ASSISTANT PROFESSOR
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2. Piezoelectric transducer
 The piezo transducer converts the physical quantity into an electrical voltage
which is easily measured by analogue and digital meter.
 The piezoelectric transducer uses the piezoelectric material which has a special
property, i.e. the material induces voltage when the pressure or stress applied to
it.
 The material which shows such property is known as the electro-resistive
element.
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3. Contd..
 The Piezoelectric transducer is an electroacoustic transducer use
for conversion of pressure or mechanical stress into an
alternating electrical force.
 It is used for measuring the physical quantity like force, pressure, stress,
etc., which is directly not possible to measure.
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4. Piezo electric materials
 The word piezoelectric means the electricity produces by the pressure.
 The Quartz is the examples of the natural piezoelectric crystals, whereas
the Rochelle salts, ammonium dehydration, phosphate, lithium sulphate,
dipotassium tartrate are the examples of the man made crystals.
 The ceramic material is also used for piezoelectric transducer.
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5. Contd..
 The ceramic material does not have the piezoelectric property.
 The property is developed on it by special polarizing treatment.
 The ceramic material has several advantages.
 It is available in different shapes and sizes.
 The material has the capability of working at low voltages, and also it can operate at the
temperature more than 3000ºC
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6. Contd..
 The pressure is applied to the crystals with the help of the force summing
devices for examples the stress is applied through mechanical pressure
gauges and pressure sensors, etc.
 The deformation induces the EMF which determines the value of applied
pressure
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7. Piezoelectric Effect
 A piezoelectric transducer is based on the
principle of the piezoelectric effect.
 The word piezoelectric is derived from the Greek
word piezen, which means to squeeze or press.
 The piezoelectric effect states that when
mechanical stress or forces are applied on quartz
crystal, produce electrical charges on the quartz
crystal surface.
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8. Piezoelectric Effect
The piezoelectric
effect is
discovered by
Pierre and Jacques
Curie.
The rate of charge
produced will be
proportional to
the rate of change
of mechanical
stress applied to it.
Higher will be
stress higher will
be voltage.
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9. Properties of Piezo Electric-Crystal
The piezoelectric material has high stability.
It is available in various shapes and sizes.
The piezoelectric material has output insensitive to temperature and
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10. Working
Piezoelectric Transducer works with the principle of piezoelectricity and piezoelectric material is used.
The faces of piezoelectric material, usual quartz, is coated with a thin layer of conducting material
such as silver.
When stress has applied the ions in the material move towards one of the conducting surface while
moving away from the other.
This results in the generation of charge.
This charge is used for calibration of stress. The polarity of the produced charge depends upon the
direction of the applied stress.
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11. Different forms of stress
Compressive stress Tensile stress
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12. Piezo electric transducer circuit
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13. Construction and working
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14. Contd..
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Used for calibration of applied stress
Amplified using charge amplifier
Electric voltage is generated
Mechanical stress is applied

15. Advantages
These are active transducer i.e. they
don’t require external power for
working and are therefore self-
generating.
The high-frequency response of these
transducers makes a good choice for
various applications.
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16. Disadvantages
Temperature and environmental
conditions can affect the behavior of the
transducer.
They can only measure changing
pressure hence they are useless while
measuring static parameters.
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17. Applications of piezoelectric transducer
They are used in
seismographs to measure
vibrations in rockets.
In strain gauges to
measure force, stress,
vibrations etc…
Used by automotive
industries to measure
detonations in engines.
These are used in
ultrasonic imaging in
medical applications.
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18. Piezoelectric pressure sensors
 Piezoelectricity is the charge created across certain materials when a
mechanical stress is applied.
 Piezoelectric pressure sensors exploit this effect by measuring the voltage
across a piezoelectric element generated by the applied pressure.
 They are very robust and are used in a wide range of industrial
applications.
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19. Working principle
 When a force is applied to a piezoelectric material, an
electric charge is generated across the faces of the
crystal. This can be measured as a voltage proportional
to the pressure (see diagram to the right).
 There is also an inverse piezoelectric effect where
applying a voltage to the material will cause it to change
shape.
 A given static force results in a corresponding charge
across the sensor. However, this will leak away over time
due to imperfect insulation, the internal sensor
resistance, the attached electronics, etc.
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20.  As a result, piezoelectric sensors are not normally suitable for measuring static pressure.
 The output signal will gradually drop to zero, even in the presence of constant pressure.
 They are, however, sensitive to dynamic changes in pressure across a wide range of
frequencies and pressures.
 This dynamic sensitivity means they are good at measuring small changes in pressure,
even in a very high-pressure environment.
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21. Construction
 The piezoelectric effect requires materials with a specific asymmetry in the crystal
structure. This includes some natural crystals, such as quartz or tourmaline.
 In addition, specially formulated ceramics can be created with a suitable polarisation to
make them piezoelectric. These ceramics have higher sensitivities than natural crystals. A
useful output can be generated with as little as 0.1% deformation.
 Because the piezoelectric materials are rigid, only a very small deflection of the material
is required to get a usable output signal.
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22.  This makes the sensors very robust and tolerant of over-pressure conditions. It also means
they respond rapidly to changes in pressure.
 The pressure sensor can be affected by any external force on the piezoelectric element, for
example, by forces caused by acceleration or noise.
 Microsensors can be constructed using thin films.
 Zinc oxide was one of the first materials used. This has largely been replaced by ceramics
made from materials such as lead zirconate titanate (PZT) because of their larger piezoelectric
effect.
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23.  Micoelectromechanical systems (MEMS) can be created by combining piezoelectric thin
films with micromachined silicon membranes.
 Piezoelectric materials are also used in some other types of MEMS sensors.
 For example, the inverse piezoelectric effect is used to generate surface acoustic waves
through a diaphragm.
 The distortion of the surface under pressure can then be detected by the changes it causes
in the waves that are received by another piezoelectric element.
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24. Design
 Piezoelectric pressure sensors are often constructed in a threaded
tube (as shown in the diagram below) to make it easy to mount
them in equipment where pressure is to be monitored.
 Care is needed when installing these because over-tightening can
affect the output sensitivity.
 In some of the typical applications of piezoelectric sensors, they
may be exposed to thermal shock (a sudden change in
temperature) caused by either radiant heat or the flow of hot
gases or liquids past the sensor.
 This can cause changes to the output due to heating of the crystal,
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25. Applications
 The robustness, high frequency and rapid response time of piezoelectric pressure sensors
means they can be used in a wide range of industrial and aerospace applications where they’ll
be exposed to high temperatures and pressures.
 They are often used for measuring dynamic pressure, for example in turbulence, blast, and
engine combustion. These all require fast response, ruggedness and a wide range of operation.
 Their sensitivity and low power consumption also makes them useful for some medical
applications. For example, a thin-film plastic sensor can be attached to the skin and used for
real-time monitoring of the arterial pulse.
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26. Advantages
Piezoelectric sensors can be used at high temperatures.
The output signal is generated by the piezoelectric element itself, so they are inherently
low-power devices.
Piezoelectric sensors can be easily made using inexpensive materials (for example quartz
tourmaline), so they can provide a low cost solution for industrial pressure measurement.
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27. Disadvantages
 The sensitivity may change with temperature but this can be minimized by appropriate
choice of materials.
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