Chapter7 - Sensors.ppt - BEKG 1233 PRINCIPLES OF...

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1 CHAPTER 7 - SENSORS / TRANSDUCERS BEKG 1233 – PRINCIPLES OF INSTRUMENTATION AND MEASUREMENT
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2 Objectives At the end of this chapter, students should be able to: Explain the operation and function of the transducer/sensor Explain the application of the transducer/sensor Explain the limitation of certain transducer/sensor Differentiate several function of transducer in order to choose the correct type of transducer in instrumentation application.
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3 Introduction A transducer is defined as a device that receives energy from one system and transmits it to another, often in a different form (electrical, mechanical or acoustical). Basically, there are two types of transducers : 1) Electrical 2) Mechanical The electrical output of a transducer depends on the basic principle involved in the design. The output may be analog, digital, or frequency modulated.
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4 Electrical Transducer An electrical transducer is a device that converts a physical, mechanical or optical quantity into a proportional voltage or current quantity. An electrical transducer must have the following parameters : 1) Linearity Linear relationship between a physical parameter and the resulting electrical signal. 2) Sensitivity Defined as the electrical output per unit change in the physical parameter (eg. V/ 0 C) High sensitivity is desirable.
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5 Electrical Transducer 3) Dynamic Range Transducer must have a wide operating range. 4) Repeatability The input/output relationship for a transducer should be predictable over a long period of time. 5) Physical Size The transducer must have minimal weight and volume to minimize the disturbance to the existing conditions/environment.
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6 Electrical Transducer Electrical transducers can be classified into two major categories : 1) Active transducers Generates an electrical signal directly in response to the physical parameter (does not require external power to operate). Example : piezo-electric sensor and photo cells. 2) Passive transducers Requires external power to operate. Example : Strain gauges and thermistors.
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7 Electrical Transducer Electrical transducers are used mostly to measure non- electrical quantities. A transducer which converts a non-electrical quantity into an analog electrical signal consists of two parts the sensing element ant the transduction element . Sensing element – responds to a change in a physical phenomenon. Transduction element – transforms the output of a sensing element to an electrical output.
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8 Electrical Transducer The different electrical phenomena employed in the transduction elements of transducers are as follows: Resistive Inductive Capacitive Electromagnetic Piezo-electric Photo-emmisive Photo-resistive Potentiometric Thermo-electric Frequency generating
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9 Resistive Position Transducer Operates under a principle of resistance change by the physical movement under measurement.
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  • Fall '17
  • puan nor azilah binti ahmad
  • Transducer, NORIZAN, Linear Inductive Transducer, Angular Inductive Transducer

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