Presented byMd. Bashir Uddin
Roll: 1215502
Dept. of BME
KUET, Khulna-9203
A transducer is a device that changes one form of
energy into another.
Microphone
Sound
Speaker
Electric signal
A
Electric signal
Sound
transducer is placed at the
input of a measurement system.
A physiological transducer is a device that
changes physiological variables into
electrical signal.
Physiological
variable
Transducer
Electrical
Signal
Block diagram of physiological transducer
 A variable associated with the physiological
process of the body is called Physiological variable
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Ionic potentials & currents
Mechanical movements
Hydraulic pressure & flow
Temperature
Chemical reaction and many more
Electrical
 Electro-mechanical
 Electromagnetic
 Photonic
 Photovoltaic, or any other
form of energy.
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Transducer consists of 2 parts

Sensing or detector element
Transduction element
 Sensing
or detector element senses or
responses to physical phenomena or
change in a physical object/body.
 Transduction
element transforms the
output of sensing to an electrical output.
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Accuracy
Sensitivity
Threshold
Noise
Linearity
5 categories:
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Based on principal of transduction
Primary or Secondary
Passive or Active
Analog or Digital
Transducer and Inverse Transducer
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Thermo electric
Magneto resistive
Electro kinetic
Optical
Resistive
Inductive
Capacitive
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Bourdon tube acts as a primary transducer
which converts pressure into displacement.
The linear displacement then convert into
electrical voltage by linear variable
differential transformer which acts as a
secondary transducer.
Active Transducer: No external power
reqd. to produce I/p. It draws power
from input applied.
Example: Piezo electric x’tal used for
accelartion measurement.
Passive Transducer: External power
required for transduction. So it is
externally powered.
 Example : Resistive (Strain Gauge),
Inductive (LVDT), Capacitive Transducers.
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Analog Transducer: Convert I/p quantity
into an analog o/p. Analog o/p is a
continuous function of time.
Example: Strain gauge, LVDT, thermocouple
Digital Transducer: Converts I/p
quantity into an electrical o/p in the
form of pulses.
Example: Digital Encoder
Transducer: Convert nonelectrical variables
into electrical parameters.
 Example: Microphone
Inverse Transducer: Converts electrical
signal to physical quantity.
 Example: Speaker
Physical variable
Types of transducer
Force
Piezoelectric
Unbounded strain gage
Displacement
Variable Resistance
Variable inductance
Variable capacitance
Linear Variable differential
transducer
Mercury strain gage
Velocity
Magnetic Indection
Temperature
Thermocouple
Thermostat
Light
Photo voltaic
Photo electric
Magnetic field
Hall effect