This document discusses transducers, which are devices that convert one form of energy into another. It describes various types of transducers such as temperature, displacement, and resistance transducers. Transducers are classified based on the transduction form used, whether they are primary or secondary, passive or active, analog or digital. Key factors in selecting a transducer include operating principle, sensitivity, range, accuracy, and environmental compatibility. The basic construction of a transducer includes a sensing element that responds to changes and a transduction element that converts this to an electrical signal. Transducers have applications in equipment like audio/video and advantages like remote output and electrical amplification.

2. CONTENTS
WHAT IS TRANSDUCER
 CLASSIFICATION OF TRANSDUCERS
 SELECTION CRITERIA OF THE TRANSDUCERS
 BASIC CONSTRUCTION OF TRANSDUCERS
 APPLICATIONS
 ADVANTAGES AND DISADVANTAGES

3. WHAT IS
TRANSDUCER ?!
The transducer is defined as the device which
convert the one form of energy into another form
of the energy
Example:
 Temperature transducers
 Thermocouples
Displacement transducers
 Thermistors

4. CLASSIFICATION OF
TRANSDUCERS
 On the basis of transduction form used.
 Primary and secondary transducers.
 Passive and active transducers.
 Analog and digital transducers.
 Transducers and inverse transducers

5. On the basis of transduction form
used
 Resistive Transducers.
 Capacitive Transducers.
 Inductive Transducers.
 Voltage and current Generating Transducers.

6. Primary and secondary
transducers
Primary transducer:
The Mechanical device which
converts physical quantity to be measured into a
mechanical signal.
Secondary transducer:
The Electrical device which
converts this mechanical signal to the electrical
signal.
Example:
LVDT and bourdon tube

7. Passive and Active
Transducers
 If transducers derive the power require for
transduction from an power source, then this
kind of transducer are known as passive
transducer
Example
 LVDT (Linear voltage differential
transformer)
 RVDT (Rotary voltage differential
transformer)

8. CONT…
When there is no need for any source then
these type of transducers are Active
transducers
Example are :
Thermocouple
Piezoelectric crystal

9. THERMOCOUPLE
 A device for measuring temperature in
which a pair of wires of dissimilar metals (as
copper and iron) are joined and the free ends
of the wires are connected to an instrument
(as a voltmeter) that measures the difference
in potential created at the junction of the two
metals.

10. Piezoelectric crystal
 Quartz ,Rochelle salt, Lithium sulphate or barium
titanate.
Quartz Rochelle Salt

11. Inverse Transducers
These type of transducers convert a electrical
quantity into non-electrical quantity
Example
Piezoelectric crystal
Analog ammeter
voltmeter

12. SELECTION CRITERIA OF THE
TRANSDUCERS
 Operating principle
 Sensitivity
 Operating range
 Accuracy
 Errors
 Environmental capability
 Insensitive to unwanted Signal
 Stability

13. Transducers selection
factors
Operating Principle: The transducer are many
times selected on the basis of operating principle
used by them. The operating principle used may
be inductive, resistive, capacitive , piezo-electric,
optoelectronics etc.
Sensitivity: The transducer must be sensitive
enough to produce detectable output.
Operating Range: The transducer should maintain
the range requirement and have a good resolution
over the entire range.
Accuracy: High accuracy is assured

14. Contd……
Errors: The transducer should maintain the expected
input-output relationship as described by the transfer
function so as to avoid errors.
 Environmental Compatibility: It should be assured
that the transducer selected to work under specified
environmental conditions maintains its input- output
relationship and does not break down.
 Insensitive to unwanted signal: : The transducer
should be minimally sensitive to unwanted signals and
highly sensitive to desired signals.
 Stability: The ability of sensor to retain its
characteristics over a relatively long period of time

15. BASIC CONSTRUCTION OF
TRANSDUCERS
It consist of two important parts
 Sensing element: Also known as SENSOR .It
is a device producing measurable response to
change in physical condition.
 Transduction element: The transduction
element convert the sensor output to suitable
electrical form.

16. APPLICATION
 Audio/video equipment
 Pressure indication
 Measurement of displacement
 Alarms

17. ADVANTAGES
 Power requirement is very low for controlling
the electrical or electronic system.
 Output can be indicated and recorded remotely
from the sensing element.
 Electrical amplification and attenuation can be
easily done.
 An amplifier may be used to amplify the
electrical signal according to requirement.

18. DISADVANTAGES
 Their cost is high
 Thermistors are unsuitable for wide
temperature
 Relative large displacement is
required for appreciable output for
LVDT
 Bourdon tubes do not provide the
precise measurement.