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OBJECTIVES:OBJECTIVES:
By the end of this chapter, you should:-By the end of this chapter, you should:-
•Understand more fully the role and functioning of thebasic instruments in closed loop control system.•Understand more fully the role and functioning of thebasic instruments in closed loop control system.
•Be able to define and give an example•Be able to define and give an example
–Measuring Element–Measuring Element
–Control Element–Control Element
–Final Control Element–Final Control Element
–Data Presentation Element–Data Presentation Element
–Process–Process
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CLOSED LOOP CONTROL SYSTEMCLOSED LOOP CONTROL SYSTEM
MEASURING
ELEMENT
SetPoint
CONTROL
LAW
FCE
PROCESS
x
y
z
w
e
CONTROLLER
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PROCESS
x
PROCESSPROCESS
•Definition: Physical or chemical change of matter orconversion of energy•Definition: Physical or chemical change of matter orconversion of energy
•Example: change in•Example: change in
–Pressure–Pressure
–Flow–Flow
–Level–Level
–Temperature–Temperature
–Speed–Speed
–Electrical Potential–Electrical Potential
–etc–etc
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MEASURING
ELEMENT
MEASURING ELEMENTMEASURING ELEMENT
•Definition: Consist of a sensor and transmitter.•Definition: Consist of a sensor and transmitter.
•Example:•Example:
–Temperature: Thermocouple, Resistance TemperatureDetector (RTD)–Temperature: Thermocouple, Resistance TemperatureDetector (RTD)
–Pressure: Manometer, Bourdon tube, Diaphragm, Bellows–Pressure: Manometer, Bourdon tube, Diaphragm, Bellows
–Flow: Orifice Plate, Venturimeter, Pilot Tube, Rotameter,Thermal Flow Meter, Mass Flow Meter, Turbine Flow Meter–Flow: Orifice Plate, Venturimeter, Pilot Tube, Rotameter,Thermal Flow Meter, Mass Flow Meter, Turbine Flow Meter
–Level: Differential Floats, Pressure Cells (DP Cells), Radarlevel Gauge, Ultrasonic meters, capacitance and conductancetype meters–Level: Differential Floats, Pressure Cells (DP Cells), Radarlevel Gauge, Ultrasonic meters, capacitance and conductancetype meters
–Quality: Gas Chromatograph, PH Analyzers–Quality: Gas Chromatograph, PH Analyzers
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Temperature Transmitter
4-20 mA Vibration Transmitter
MEASURING ELEMENTMEASURING ELEMENT
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TRANSMITTER
MEASURING ELEMENTMEASURING ELEMENT
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TRANSMITTER
MEASURING ELEMENTMEASURING ELEMENT
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Typical Sensors for TemperatureTypical Sensors for Temperature
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Typical Sensors for TemperatureTypical Sensors for Temperature
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Typical Sensors for LevelTypical Sensors for Level
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Typical Sensors for LevelTypical Sensors for Level
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Typical Sensors for FlowTypical Sensors for Flow
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Typical Sensors for FlowTypical Sensors for Flow
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Typical Sensors for PressureTypical Sensors for Pressure
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SetPoint
w
e
CONTROL
LAW
x
y
CONTROLLERCONTROLLER
•Definition: A device which operates automatically toregulate a controlled variable.•Definition: A device which operates automatically toregulate a controlled variable.
–Compares the CV & SP, and generates a process error signal.–Compares the CV & SP, and generates a process error signal.
–Generates a control action according to the specified controlalgorithm (PID)–Generates a control action according to the specified controlalgorithm (PID)
•Example: PID Controller, PLC, etc.•Example: PID Controller, PLC, etc.
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CONTROLLER
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FINAL CONTROL ELEMENTFINAL CONTROL ELEMENT
FCE
•Definition: The controlling element which directlychanges the value of the manipulated variable.•Definition: The controlling element which directlychanges the value of the manipulated variable.
•Example:•Example:
–Globe Valve–Globe Valve
–Butterfly Valve–Butterfly Valve
–Slider–Slider
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FINAL CONTROL ELEMENTFINAL CONTROL ELEMENT
VALVE
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RECORDER
DATA PRESENTATION ELEMENTDATA PRESENTATION ELEMENT
Example:Example:
–Recorder–Recorder
–Oscilloscope–Oscilloscope