Md. Bashir Uddin

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Transducer for Physical Parameters
Presented by- Md. Bashir Uddin Roll
1215502 Dept. of BME KUET, Khulna-9203
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Transducers

• A transducer is a device that changes one form of
  energy into another.
• Sound
  Electric signal
• Electric signal
  Sound

Microphone
Speaker

• A transducer is placed at the input of a
  measurement system.

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Physiological Transducer

• A physiological transducer is a device that
  changes physiological variables into electrical
  signal.

Transducer
Physiological variable
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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Different forms of Physiological variables

• Ionic potentials currents
• Mechanical movements
• Hydraulic pressure flow
• Temperature
• Chemical reaction and many more

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Transducer energy conversion

• Electrical
• Electro-mechanical
• Electromagnetic
• Photonic
• Photovoltaic, or any other form of energy.

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Construction of Transducer

• 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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Performance Characteristics of Transducer

• Accuracy
• Sensitivity
• Threshold
• Noise
• Linearity

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Classification of Transducer

• 5 categories
• Based on principal of transduction
• Primary or Secondary
• Passive or Active
• Analog or Digital
• Transducer and Inverse Transducer

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Based on Principle of Transduction

• Thermo electric
• Magneto resistive
• Electro kinetic
• Optical
• Resistive
• Inductive
• Capacitive

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Primary or Secondary Transducer

• 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.

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Active Passive Transducers

• Active Transducer No external power reqd. to
  produce I/p. It draws power from input applied.
• Example Piezo electric xtal 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 Digital Transducers

• 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
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Transducer Inverse Transducer

• Transducer Convert nonelectrical variables into
  electrical parameters.
• Example Microphone
• Inverse Transducer Converts electrical signal to
  physical quantity.
• Example Speaker

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Transducer Sensor Outputs
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Transducer for biomedical Application
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
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THANK YOU