tranducers..

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.