TRANSDUCER AND IT’S APPLICATIONS
SARRAJUSNEHA
Student of Electronics & Communication Engineering (2nd Year), Amity University, Lucknow
Abstract- Simple stand alone electronic circuits can be made to repeatedly flash a light or play a musical note,
but in order for an electronic circuit or system to perform any useful task or function it needs to be able to
communicate with the “ real world “ whether by reading an input signal from an “ON/OFF” switch or by
activating some form of output device to illuminate a single light. An electronic system or circuit must be able to
“do” something and sensors , transducers are the perfect components for doing this. The word “ transducer “ is the
collective term used for both Sensors which can be used to sense a wide range of different energy forms such as
movement, electrical signals, radiant energy , thermal or magnetic energy etc; and Actuators which can be used to
switch voltages or currents. There are many different types of sensors and transducers , both analog and digital and
input and output available to choose from. The type of input or output transducer being used , really depends
upon the type of signal or process being “sensed” or “controlled” but we can define a sensor and transducers as
devices that converts one physical quantity into another. Devices which perform an “Input “ function are
commonly called sensors because they “sense” a physical change in some characteristic that changes in response to
some excitation, for example heat or force and convert that into an electrical signal. Devices which perform an
“output” function are generally called Actuators and are used to control some external device, for example
movement or sound.
resistance ,capacitance , inductance , piezo electric
and thermal effects.
I. INTRODUCTION
A transducer is a device that converts a signal in
one form of energy to another form of energy. Energy
types include electrical, mechanical, electromagnetic
(including light), chemical, acoustic or thermal
energy. While
the term transducer commonly
implies the use of a sensor / detector, any device
which converts energy can be considered a transducer
.Transducers are widely used in measuring
instruments. A sensor is used to detect a parameter
in one form and report it in another form of energy,
often an electrical signal. For example, a pressure
sensor might detect pressure (a mechanical form of
energy) and convert it to electricity for display at a
remote gauge. An actuator accepts energy and
produces movement (action).
II. CLASSIFICATION OF TRANSDUCERS
The transducers can be further classified as follows :
I. Active and passive transducers
II. Analog and digital transducers
III. On the basis of transduction principle used
IV. Primary and secondary transducer
V. Transducers and Inverse transducers.
III. ACTIVE AND PASSIVE TRANSDUCERS
Active Transducers:
 These transducers do not any external
source of power for
their operation.
Therefore they are also called as selfgenerating type transducers.
 The active transducer are self - generating
devices which operate under the energy
conversion principle.
 As the output of active transducers , we
get an equivalent electrical output signal
e.g. temperature or strain to electrical
potential ,without any external source of
energy being used.
The energy supplied to an actuator might be electrical
or mechanical (pneumatic, hydraulic, etc.).An electric
motor and a loudspeaker are both actuators,
converting electrical energy into motion for different
purposes.
Transducers have both functions; they both detect
and create action. For example , a typical ultrasonic
transducer switches back and forth many times a
second between acting as an actuator to produce
ultrasonic waves ,and acting as a sensor to detect
ultrasonic waves .Rotating a DC electric motor’s
rotor
will produce electricity and voice-coil
speakers can also act as microphones .
Examples:
Photo voltaic, Thermo- Electric, Electro – magnetic,
Piezo-electronic, chemical and others.
Passive Transducers:
These transducers need external source of power
for their operation .so they are not self generating type transducers.
Transducers converts energy from one form into
another and the output as electrical signal by
using the principal effects like variation in
Proceedings of 9th IRF International Conference, Chennai, India, 25th May. 2014, ISBN: 978-93-84209-22-3
1
Transducer and It’s Applications


Digital Transducer:
Digital transducers create non –continuous pulses
which are naturally disjoined. Common examples
are laser beam instruments and vortex flow
meters.
A DC power supply or an audio
frequency generator is used as an
external power source .
These transducers produce the output
signal in the form of variation in
resistance ,capacitance, inductance,
or
some other electrical parameter in response
to the quantity to be measured.
V. ON
THE
BASIS
TRANSDUCTION PRINCIPLE USED
Examples:
Resistance, Hall- effect type, Opto-electronic( photo
emissive & photo conductive ),variable reactance
etc.
OF
 By
transduction principle , transducers
can further be classified as follows
Example:
1. Capacitive transduction
2. Electro-magnetic transduction
3. Photo-conductive transduction
4. Inductive transduction
5. Photo-voltaic transduction
6. Piezo-electric transduction etc.
IV. ANALOG AND DIGITAL TRANSDUCERS:
Analog Transducer:
 Analog transducers transmit a readable
continuous analog reading of whatever
input it receives. Typical of this type
of transducer are the thermistor and
strain-gauge.
Strain –gauge:
 The strain-gauge is a passive, resistive
transducer which converts the mechanical
elongation and compression
into
a
resistance change .
 This change in resistance takes place due
to variation in length and cross sectional
area of the gauge wire , when an external
force acts on it .
VI.
PRIMARY AND SECONDARY
TRANSDUCERS

Some transducers contain the mechanical
as well as electrical device. The mechanical
device converts the physical quantity to be
measured into a mechanical signal .such
mechanical device
are called
as the
primary transducers , because they deal
with the physical quantity to be measured.
 The electrical device then convert this
mechanical signal into a corresponding
electrical signal. Such electrical device is
known as secondary transducers.
The type of strain gauge are as
1. Wire gauge
a) Unbounded
b) Bonded
c) Foil type
VII. TRANSDUCERS
TRANSDUCERS
1.
AND
INVERSE
Transducer converts non- electrical quantity
to electrical quantity.
Inverse transducer
converts
electrical
quantity to a non-electrical quantity.
USES OF TRANSDUCERS
2. Semiconductor gauge
Thermistor:
 It is a contraction of a term “ thermal
resistor “
 Thermistor is temperature dependent
resistors. They are made of semiconductor material which have negative
temperature coefficient of resistivity i.e.,
their resistance decreases with increase of
temperature.
 Thermistors are widely
used in
application which involve measurement in
the range of 0-60
. thermistor are
composed of sintered mixture of metallic
oxides such as manganese, nickel, cobalt,
copper, iron & uranium.
A transducer is a device that converts one form
of energy to another, usually as a transmitter,
receiver or sensor . Different kinds of transducers
use different forms of energy such as sound ,
light and electricity to make visual signals , sense
movement and measure forces. In
many
instances,
transducers are used
to
make
equipment safer. A
light sensor can ,
for
example , sense the presence of a person’s hand
and switch off dangerous machinery.
See beck effect:
When a pair of dissimilar metals are joined at
one end , and there is a temperature difference
between the joined end , & the open ends,
thermal emf is generated , which can be
measured in the open ends.
Position Measurement:
An ultrasonic transducer measures the distance to
an object by sending out pulses of high frequency sound and processing the echoes that
bounce back. They can measure distances from a
2.
3.
Proceedings of 9th IRF International Conference, Chennai, India, 25th May. 2014, ISBN: 978-93-84209-22-3
2
Transducer and It’s Applications
few inches to over 100 feet in a fraction of a
second . This method is suitable for measuring
the distance along an unobstructed path to any
object more than a few inches in size. Measuring
systems use computer software to track position
,
velocity and acceleration based on these
signals.
concentration.
Microelectrodes
in
biomedicine measure voltages from cells.
Ultrasound transducers in medicine serve
as probes
for cardiologists
and
obstetricians.Loudspeakers
and
microphones convert sound energy into
electrical energy .In
robotics, stepper
motors convert electrical signals into
rotary positions. CCD detector arrays ,
used in a variety of science
and
engineering projects, take light patterns
and transform them into electronic
images
that may be
manipulated.
Transducer
signals can be captured
directly by USB,
parallel or serial
computer ports or by sound cards. Data
acquisition can also be done with DAQ
cards made especially for that purpose
.some signals are also transmitted to the
computer
wirelessly.Scientists
and
engineers often write their own programs
in languages such as BASIC or C++ to
capture and manipulate transducer signals
.other
options
include
commercial
software such as Lab view or Mat lab ,or
freeware
such
as
Glove or visual
analyser.A
transducer is known to
consist of more than one physical
element , in which case it is treated as a
system. The pattern of connection of the
several elements may result in an openloop system (or) a closed- loop system.
The closed-loop configuration offers
several advantages in the measurement
and hence feed-back type transducers are
used
in many
situations.Thus
the
applications of transducers are in various
ways
like
electromagnetic
,
electrochemical,
electromechanical,
electroacoustic , electro –optical (
photoelectric), electrostatic , thermoelectric
and radio acoustic etc.
Proximity Detector:
Though
related
to measuring distance , a
proximity detector has a slightly different job : it
senses if an object is close . Hall-effect
transducers are frequently used for proximity
detection , as they are inexpensive, are easy to
use, and have no moving parts . The hall effect
creates a small voltage in materials in the presence
of a magnetic field. This has some important
advantages : an object doesn’t have to be
touching the transducer to be detected and it can
detect anything that may have a small magnet
attached to it. The solid-state nature of hall-effect
transducers means that they can sense thousands
of proximity changes per second and operate for
years without wear.
Sound:
Loud speakers
also fit the definition of
transducers. They convert electrical energy into
small movements that make sound. Most loud
speakers are made of a thin cone of material ,
such as paper or plastic , attached to a wire
coil. A strong magnet sits near the coil , so
when electric current flows through the coil ,
magnetic forces make the cone move back and
forth .If this movement is at audio frequencies , it
produces sound .The basic design works for a
wide range of sizes , from tiny ear buds to large
theatre speakers.
CONCLUSION
 Though the most common types of
transducers convert physical quantities
such as temperature
in to electrical
quantities such as voltage or current ,or
vice versa, they are not limited to these
kinds of conversions. Mechanical energy
can be changed into electrical energy or
another form of mechanical energy , for
instance .The signals that transducers
produce can be processed and manipulated
by devices such as computers and circuits.
These signals can also be used to control
other instruments and processes. In high
–energy physics , transducers detect
particles , and in biology and chemistry ,
they form probes that can measure ion
ACKNOWLEDGEMENTS:
I sincerely , thank each and everyone especially
my parents who supported and encouraged me in
doing this research paper.
REFERENCES
[1]. www.books.google.co.in
[2]. Transducers and Instrumentation by D.V.S. Murty.
[3]. www.furisonelectric.com
[4]. http://en.wikipedia.or
[5]. http://www.instrumentationtoday.com

Proceedings of 9th IRF International Conference, Chennai, India, 25th May. 2014, ISBN: 978-93-84209-22-3
3