INSTRUMENTATION

Why Instrumentation?For measurement of physical parameters in the process and control of these parameters.Measurement

Control System

InstrumentationControlProcess

Physical Quantities For Measurement Temperature Pressure Level Flow Speed Weight Gas Analysis Displacement

Types Of ControlsControl Elements: Pneumatic Control Valves Hydraulic Cylinders Electrical Control Valves On/Off Control Continuous Control

Types Of Control Systems Open Loop Control System Closed Loop Control System

Temperature MeasurementMEASUREMENTSThe temperature of a substance or medium is a phenomenon expressing its degree of hotness or coldness.Various primary effects with respect to change in Temperature can be utilised for measurement: Change in physical or chemical state Variation in electrical parameters Generation of EMF Change in intensity of radiation

Temperature MeasurementMEASUREMENTSThermometersElectrical InstrumentsPyrometers Expansion Thermometers Filled System Thermometers Resistance Thermometers Thermocouples Thermistor Radiation Pyrometers Optical PyrometersMeasuring Elements

Temperature MeasurementMEASUREMENTSMost Commonly Used Measuring Elements: THERMOCOUPLES PRINCIPLE : A current flows in a closed circuit made up of two dissimilar metals if the junctions of the two metals are kept at different temperatures. Thus the EMF generated is proportional to the temperature difference in a predictable manner. This phenomenon is known as Seebeck effect.ThermocoupleTransmitter

Temperature MeasurementMEASUREMENTSTHERMOCOUPLES Typical Arrangement: Most Commonly Used Measuring Elements:

Temperature MeasurementMEASUREMENTS RTDs (Resistance Temperature Detectors) Most Commonly Used Measuring Elements: PRINCIPLE : The resistivity of metals increases or decreases with increase in temperature. Such variations can be measured precisely with suitable electrical circuitsRTDTransmitterUsed for low temperature, high accuracy measurements.

Temperature MeasurementMEASUREMENTSRTDs 3-Wire System4-Wire System

Temperature MeasurementMEASUREMENTSRTDs Typical Arrangement:

Temperature MeasurementMEASUREMENTSSelection Criteria

Pressure MeasurementMEASUREMENTSPressure is defined as the amount of force appliedto a surface or distributed over it.It is measured as force per unit area.Different types of pressure: Gauge Pressure: Atmosphere pressure is considered as zero point. Absolute Pressure: Atmosphere pressure is included. Vacuum Pressure: Pressure below zero. Differential Pressure: Difference in two pressure heads.

Pressure MeasurementMEASUREMENTSManometersElastic TransducersMeasuring ElementsElectrical Transducers

Pressure MeasurementMEASUREMENTSMost Commonly Used Measuring Elements: MANOMETERSOrificeScaleh1High Pressure Tap P1Low Pressure Tap P2Principle:P= (- 1) g hWhere = Density of fluid in U tube 1= Density of fluid in pipe h = h2-h1 g = acceleration due to gravity

Pressure MeasurementMEASUREMENTSMost Commonly Used Measuring Elements: DIAPHRAM TRANSDUCERSPrinciple: PRESSURE

Pressure MeasurementMEASUREMENTSMost Commonly Used Measuring Elements: Principle:DIFFERENTIAL PRESSUREDIAPHRAM TRANSDUCERS

Pressure MeasurementMEASUREMENTSMost Commonly Used Measuring Elements: Typical Arrangement:

Flow MeasurementMEASUREMENTSDetermination of proportions and amount of materials flowing in or out of a process.Various Methods For Flow Measurement: Variable head or differential Variable Area Magnetic Thermal Ultrasonic

Flow MeasurementMEASUREMENTSMost Commonly Used Measuring Elements: DIFFERENTIAL FLOWMETERSPrinciple:

Flow MeasurementMEASUREMENTSMost Commonly Used Measuring Elements: MAGNETIC FLOWMETERSPrinciple: Uses Faradays Law Of Electromagnetic Induction-

Whenever a conductor moves through a magnetic field of given strength, a voltage is induced in the conductor which is proportional to velocity between the conductor and the magnetic fieldIn case of magnetic flow meter, electrically conductive flowing liquid acts as a conductor.

Level MeasurementMEASUREMENTSDirect MethodsIndirect MethodsMeasuring Methods Hook Type Sight Glass Float Type Hydrostatic Type Electrical Type Pressure Type Bubbler Type Capacitance Type Radiation Type

Level MeasurementMEASUREMENTSMost Commonly Used Measuring Elements: PRESSURE TYPEPrinciple:

Level MeasurementMEASUREMENTSMost Commonly Used Measuring Elements: BUBBLER TYPEPrinciple:

Level MeasurementMEASUREMENTSMost Commonly Used Measuring Elements: CAPACITANCE TYPEPrinciple: The probe acts as one of the terminal of a large earthed capacitorC=K . A/D Where C = Capacitance K = Dielectric Constant A = Area Of Plate D = Distance Between Plates

Level MeasurementMEASUREMENTSMost Commonly Used Measuring Elements: CAPACITANCE TYPETypical Arrangement:

Level MeasurementMEASUREMENTSMost Commonly Used Measuring Elements: RADIATION TYPE

Speed MeasurementMEASUREMENTSTacho GeneratorsContactless TachometersMeasuring Elements

Speed MeasurementMEASUREMENTSMost Commonly Used Measuring Elements: AC TACHO GENERATORSPrinciple:

Speed MeasurementMEASUREMENTSMost Commonly Used Measuring Elements: DC TACHO GENERATORSPrinciple:

Speed MeasurementMEASUREMENTSMost Commonly Used Measuring Elements: NONCONTACT TACHOMETERSPrinciple:

Weight MeasurementMEASUREMENTSLOADCELLSPRINCIPLE: The change in resistance of strain gauge is proportional to the weight supported by the cellWhere R= Change In Resistance L = Change In Length

Displacement MeasurementMEASUREMENTSLVDT (Linear Voltage Differential Transducer)

Gas AnalysisMEASUREMENTSMost Commonly Used Measuring Elements: CO-Analysers

Gas AnalysisMEASUREMENTSMost Commonly Used Measuring Elements: O2-Analysers

CONTROL ELEMENTSGeneral Assembly

CONTROL ELEMENTSValves

CONTROL ELEMENTSValvesMost Commonly Used Control Elements: BUTTERFLY VALVES

CONTROL ELEMENTSValvesMost Commonly Used Control Elements: BALL VALVES

CONTROL ELEMENTSActuatorsTypical Arrangement Pneumatic Actuators :

CONTROL ELEMENTSActuatorsTypical Arrangement Hydraulic/Pneumatic Cylinder:Electrical Actuator:

CONTROL ELEMENTSActuating Instruments Solenoids (On/Off Control)

CONTROL ELEMENTSActuating InstrumentsPositioners Or I to P Converters(Continuous Control)Pneumatic Positioners

CONTROL SYSTEMOpen Loop Control System

CONTROL SYSTEMClosed Loop Control System

CONTROL SYSTEMExample

CONTROL SYSTEMTypical Arrangement