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5. TRANSDUCERS & SENSORS

5. TRANSDUCERS & SENSORS. 13 Marks. INSTRUMENTATION SYSTEM. TRANSDUCER. Definition:- It is device which convert physical quantity which is to be measured in to an equivalent electrical signal (voltage or current). Functions of transducer:

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5. TRANSDUCERS & SENSORS

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  1. 5. TRANSDUCERS & SENSORS 13 Marks

  2. INSTRUMENTATION SYSTEM

  3. TRANSDUCER • Definition:- It is device which convert physical quantity which is to be measured in to an equivalent electrical signal (voltage or current). Functions of transducer: 1) To detect & sense parameter,magnitude & any change in physical quantity. 2) To provide proportional electrical output signal.

  4. Selection Criteria of Transducer • Linearity • Accuracy • Sensitivity • Operating Range • Minimum sensitivity • Frequency responded • Speed of response • Reliability • Cost of sensors • Output power • Nature of output • Maintenance of sensor

  5. TRANSDUCER CHARACTERISTIC STATIC CHARACTERISTICS DYNAMIC CHARACTERISTICS Output of transducer is time dependent w.r.t. to variation input of transducer Types: Response time Rise time Time constant Setting time • Output of transducer is time independent w.r.t. to variation input of transducer

  6. COMPARISON BETWEEN ACTIVE & PASSIVE TRANSDUCER Active Transducer Passive Transducer External power supply is required Primary transducer This transducer convert measurement into variation in resistance capacitance Examples: Thermistors, LDR, LVDT, Photo Transistor • No external power supply is required • Secondary transducer • This transducer convert measurement input into electrical signal • Examples: Thermocouple, photo voltage sensor, photo cell, piezoelectric transducer

  7. CLASSIFICATION OF TRANSDUCERS • Primary & Secondary Transducers • Passive & Active Transducers • Analog & Digital Transducers • Mechanical & Electrical Transducers

  8. PRIMARY TRANSDUCER • The Transducer which responds to the change in physical quantity & convert in to non-electrical quantity is called as Primary Transducer. • E.g. Strain gauge

  9. SECONDARY TRANSDUCER • The transducer which responds to physical quantity & convert it into Analog electrical quantity is called as Secondary Transducer. • E.g. Photo diode, Quartz crystal

  10. Passive Transducers • The transducer which require external power source for its operation is called passive transducers. • E.g. LDR

  11. Active Transducers • The transducers which do not require external power source for their operation is called Active Transducers. • E.g. Thermocouple

  12. Analog Transducers • The transducers which convert input quantity in to analog output as a continuous function of time is called as Analog transducers. • E.g. LVDT

  13. Digital Transducers • The transducer which converts the input quantity into electrical output in the form of pulses is called as Digital transducers. • Pressure sensor

  14. ELECTRICAL TRANSDUCER • Definition: Transducer which convert physical quantity is to be measured in to electrical quantity. e.g. Thermistor : temperature to electrical LDR: light to electrical photo diode: light to electrical photo transistor: light to electrical

  15. MECHANICAL TRANSDUCER • Definition: Transducer which convert physical quantity is to be measured in to mechanical quantity such as pressure, displacement etc. e.g. Diaphragms: pressure to displacement Bellows: pressure to displacement Bourdon tube: pressure to displacement Capsule: pressure to displacement

  16. Comparison of & Passive Transducers Passive Transducer Active Transducer It operates under energy conversion principle. Not require external power supply. The energy required for the production of the output signal is obtained from the physical quantity. E.g. Photovoltaic cell, Piezoelectric crystal etc. • It operates under energy controlling principle. • It require external power supply. • The energy required for the production of the output signal is obtained from the power supply. • E.g. Thermistors, strain gauge, LDR etc.

  17. Comparison of Electrical & Mechanical Transducers Mechanical Transducers Electrical Transducers It needs power supply. There are no moving parts. It is more reliable. It has more life span. It require less operating time. E.g. LVDT, Photovoltaic cell, piezoelectric crystal etc. • It does not need power supply. • There are moving parts. • It is less reliable. • It has less life span. • It require more operating time. • E.g. Manometers, Hydrometer, bellows etc.

  18. Comparison of Analog & Digital Transducers Analog Transducer Digital Transducer The transducer which converts the input quantity into electrical output in the form of pulses is called as Digital transducers. Its output is digital in nature. E.g. Rotary encoder, shaft encoder etc. • The transducers which convert input quantity in to analog output as a continuous function of time is called as Analog transducers. • Its output is analog in nature. • E.g. Thermistors, Strain gauge etc.

  19. Resistive Transducers • The transducer that covers the parameters to be measured into change in resistance which can be calibrated in terms of the measurand is called as Resistive Transducer. • E.g. LDR, Strain gauge etc.

  20. Strain Gauge • Strain gauge is an elastic resistive transducer, which converts the mechanical elongation and compression into resistance change. • Types: 1) Wire gauge 2) Foil gauge 3) Thin film gauge 4) semiconductor

  21. Inductive Transducer • The transducer that converts the measurand into change in inductance which can be calibrated in terms of the measurand is called an inductive transducer. • E.g. Inductive proximity transducer, LVDT.

  22. Linear Variable Differential Transducer

  23. Capacitive Transducer • The transducer that converts the parameters to be measured into change in capacitance, which can be calibrated in terms of measurand is called as capacitive transducer. • E.g. VCDT

  24. Piezo-Electric Transducer • Piezo-Electric Effect:- When mechanical stress or pressure is applied across the crystal, it becomes polarised and e.m.f. generated across the crystal is known as piezo-electric effect. • Piezo-electric material 1)Rochelle salt 2) Quartz

  25. Photo diode & Photo transistor • Operation of both is depending on the falling light intensity.

  26. Photo Transistor

  27. Proximity Sensors • A proximity sensor is a sensor able to detect the presence of nearby objects without any physical contact. • Types: • Inductive proximity sensor • Capacitive proximity sensor • Optical proximity sensor • Pneumatic proximity sensor • Ultrasonic proximity sensor

  28. Applications

  29. Inductive Proximity Sensor • These are proximity sensors designed to detect metal objects. • It is used in heavy duty industrial applications.

  30. Advantages of Inductive sensor • It can withstand harsh environmental conditions. • It has longer life. • It is very easy to install. • It has very predictable results and performance. • It has higher switching rate.

  31. Disadvantages of Inductive sensor • Only detects metallic object • Operating range is shorter than other sensors • Affected by strong electromagnetic field

  32. Thank You!!

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