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8/8/2019 Projects in Electrical Instrumentation
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EXPERT SYSTEMS AND SOLUTIONS
Email: [email protected]
Cell: 9952749533www.researchprojects.info
PAIYANOOR, OMR, CHENNAI
Call For Research Projects Final
year students of B.E in EEE, ECE, EI,
M.E (Power Systems), M.E (Applied
Electronics), M.E (Power Electronics)
Ph.D Electrical and Electronics.
Students can assemble their hardware in our
Research labs. Experts will be guiding theprojects.
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UNITUNIT--22
ELECTRICAL ANDELECTRICAL AND
ELECTRONIC INSTRUMENTSELECTRONIC INSTRUMENTS
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INSTRUMENTS
PRIMARY INSTRUMENTS SECONDARY INSTRUMENTS
ACCORDING TO THE NATURE ACCORDING TO THE PRINCIPLE
INDICATING INSTRUMENT
INTEGRATING INSTRUMENT
RECORDING INSTRUMENT
(i) MAGNETIC EFFECT
(ii) HEATING EFFECT
(iii) INDUCTION EFFECT
(iv) ELECTROSTATIC EFFECT
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PRIMARY INSTRUMENT:PRIMARY INSTRUMENT:
The measured quantity is mentioned throughThe measured quantity is mentioned through
its physical quantity.its physical quantity.
EX:EX:Tangent GalvanometerTangent Galvanometer
SECONDARY INSTRUMENT:SECONDARY INSTRUMENT:
The measured quantity is mentioned DirectlyThe measured quantity is mentioned Directly
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ClassificationClassification
Electrical instruments classified according toElectrical instruments classified according to
the kind of currentthe kind of current
(i) Direct Current(i) Direct Current (ii) Alternating Current(ii) Alternating Current
(iii) Both AC & DC.(iii) Both AC & DC.
(Universal Instrument)(Universal Instrument)
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According to the OperationAccording to the Operation
Electrical instrument is divided into two types.Electrical instrument is divided into two types.i) Analog Instruments.i) Analog Instruments.
(ii) Digital Instruments.(ii) Digital Instruments.
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AnalogInstrumentsAnalogInstruments
AnalogAnalog instrumentsinstruments areare nothingnothing butbut itsits outputoutput
isis thethe deflectiondeflection ofof pointer,pointer, whichwhich isis
proportionalproportional toto itsits inputinput.. ItIt isis thethe devicedevice whichwhich thethe outputoutput oror displaydisplay isis aa
continuouscontinuous functionfunction ofof timetime andand aa constantconstant
relationrelation toto itsits inputinput..
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Analog Instrument ClassificationAnalog Instrument Classification
Indicating Instrument :Indicating Instrument :
Indicate the magnitude of a quantityIndicate the magnitude of a quantity
Using Dial and a pointerUsing Dial and a pointer
Recording InstrumentRecording Instrument
Continuous record of the quantity being measuredContinuous record of the quantity being measuredover a specified period.over a specified period.
It records the variation .It records the variation .
Integrating Instrument:Integrating Instrument:
Totalize the events over a specified period of time.Totalize the events over a specified period of time.
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According to the Comparison:According to the Comparison:
DirectDirect MeasuringMeasuring InstrumentInstrument::
The measured quantity displayed directly.The measured quantity displayed directly. InIn DirectDirect MeasuringMeasuring InstrumentInstrument::
The measured quantity compared with theThe measured quantity compared with the
standard Value.standard Value.
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Digital InstrumentsDigital Instruments DigitalDigital InstrumentsInstruments areare itsits outputoutput isis inin decimaldecimal
formform
ItIt operateoperate withwith 00 andand 11ss..
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MeasuringInstrumentsMeasuringInstruments
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Ammeter and voltmeter is used to measure the voltage and current.Ammeter and voltmeter is used to measure the voltage and current.
Types of Ammeter &Voltmeter instrumentsTypes of Ammeter &Voltmeter instruments
PermanentPermanent MagnetMagnet MovingMoving coilcoil (PMMC)(PMMC)
DC ONLYDC ONLY
MovingMoving IronIron--AttractionAttraction && RepulsiveRepulsive..
Either AC or DCEither AC or DC
ElectroElectro--dynamometerdynamometer
Either AC or DCEither AC or DC
HotHot wirewire
Either AC or DCEither AC or DC
ThermocoupleThermocouple --
Either AC or DCEither AC or DC
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InductionInduction
AC ONLYAC ONLY
ElectrostaticElectrostatic Either AC or DCEither AC or DC
RectifierRectifier..
Either AC or DCEither AC or DC
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ForcesForces
Deflecting Force.Deflecting Force. Controlling Force.Controlling Force.
Damping Force.Damping Force.
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Deflecting Force or operating ForceDeflecting Force or operating Force
It is a Force used to Create the Deflection.It is a Force used to Create the Deflection.
The Force Creating system is also called as aThe Force Creating system is also called as aDeflecting System or Moving system.Deflecting System or Moving system.
It is created by any one of the Electrical Effect.It is created by any one of the Electrical Effect.
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EXPLANATIONEXPLANATION
when we are giving the supply to the Meterwhen we are giving the supply to the Meter
the corresponding changes are occurredthe corresponding changes are occurred
through the needle.through the needle.
So the Electrical system makes the Deflection .So the Electrical system makes the Deflection .
Such type of system is called as DeflectingSuch type of system is called as Deflecting
SystemSystem
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Controlling ForceControlling Force
It is used to create the control.It is used to create the control.
Such type of system is called as ControllingSuch type of system is called as ControllingSystem.System.
It is also used for create the Balance.It is also used for create the Balance.
Types:Types:
Springcontrol system.Springcontrol system.
Gravity Control system.Gravity Control system.
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EXP
LANATIONEXP
LANATION After giving the supply through DeflectingAfter giving the supply through Deflecting
System. It creates the Deflection.System. It creates the Deflection.
Due to the deflection the needle wont comes toDue to the deflection the needle wont comes tothe rest position.the rest position.
By using the controlling force it creates theBy using the controlling force it creates the
balance in the System .balance in the System .
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Damping ForceDamping Force
It is a Force used to avoid the oscillation.It is a Force used to avoid the oscillation.
It gives the Faster Action.It gives the Faster Action.
Types:Types:
Air Friction DampingAir Friction Damping
Fluid Friction DampingFluid Friction Damping Eddy current Damping systemEddy current Damping system
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EXPLANATIONEXPLANATION
The deflecting system creates the deflection in theThe deflecting system creates the deflection in themeter .meter .
The controlling system makes the controlling force.The controlling system makes the controlling force.
The controlling force is used for Balancing andThe controlling force is used for Balancing andneedle fix it in a rest position.needle fix it in a rest position.
But Thats not happened faster .due to that theBut Thats not happened faster .due to that theneedles are oscillating in the system.needles are oscillating in the system.
Such type ofProblems are minimized by usingSuch type ofProblems are minimized by using
Damping Force.Damping Force.
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Moving CoilMoving Coil
(i)(i) PMMC TypePMMC Type
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Magnet Systems :Magnet Systems :
Old style magnet system consisted of relatively longOld style magnet system consisted of relatively longU shaped permanent magnets having soft iron poleU shaped permanent magnets having soft iron pole
pieces.pieces. Owing to development of materials like Alcomax andOwing to development of materials like Alcomax and
Alnico, which have a high coAlnico, which have a high co--ercive force, it isercive force, it ispossible to use smaller magnet lengths and high fieldpossible to use smaller magnet lengths and high field
intensities.intensities. The flux densities used in PMIMC instruments varyThe flux densities used in PMIMC instruments vary
from 0.1 Wb/m to 1 Wb/m.from 0.1 Wb/m to 1 Wb/m.
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Control:Control: When the coil is supported between two jewelWhen the coil is supported between two jewel
bearings two phosphor bronze hairspringsbearings two phosphor bronze hairspringsprovide the control torque.provide the control torque.
These springs also serve to lead current in andThese springs also serve to lead current in andout of the coil. The control torque is providedout of the coil. The control torque is providedby the ribbon suspension as shown.by the ribbon suspension as shown.
This method is comparatively new and isThis method is comparatively new and isclaimed to be advantageous as it eliminatesclaimed to be advantageous as it eliminatesbearing friction.bearing friction.
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DampingDamping ::
Damping torque is produced by movement ofDamping torque is produced by movement of
the aluminum former moving in the magneticthe aluminum former moving in the magneticfield of the permanent magnet.field of the permanent magnet.
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Errors in PMMCErrors in PMMC
(i) Hysteresis Error(i) Hysteresis Error
Due to the Iron Parts Used in the Meter.Due to the Iron Parts Used in the Meter.
(ii)Temperature Error(ii)Temperature Error Due to TemperatureDue to Temperature
(iii) Stray magnetic Field Error(iii) Stray magnetic Field Error
Due to Stray Magnetic field.Due to Stray Magnetic field. It Opposes the Operating Magnetic Field.It Opposes the Operating Magnetic Field.
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ADVANTAGE:ADVANTAGE:
The scale is uniformly divided.The scale is uniformly divided.
The power consumption is very lowThe power consumption is very low
The torqueThe torque--weight ratio is high which gives a high accuracy. The accuracy is of theweight ratio is high which gives a high accuracy. The accuracy is of theorder of generally 2 percent of fullorder of generally 2 percent of full--scale deflection.scale deflection.
Using different values for shunts and multipliers may use a single instrument forUsing different values for shunts and multipliers may use a single instrument formany different current and voltage ranges.many different current and voltage ranges.
Since the operating forces are large on account of large flux densities, which maySince the operating forces are large on account of large flux densities, which maybe as high as 0.5 Wb/m, the errors due to stray magnetic fields are small.be as high as 0.5 Wb/m, the errors due to stray magnetic fields are small.
SelfSelf--shielding magnets make the core magnet mechanism particularly useful inshielding magnets make the core magnet mechanism particularly useful inaircraft and aerospace applications.aircraft and aerospace applications.
DISADVANTAGEDISADVANTAGE
These instruments are useful only for D.C.These instruments are useful only for D.C.
The torque reverses if the current reverses. If the instrument is connected to a.c., theThe torque reverses if the current reverses. If the instrument is connected to a.c., thepointer cannot follow the rapid reversals and the deflection corresponds to meanpointer cannot follow the rapid reversals and the deflection corresponds to mean
torque, which is zero. Hence these instruments cannot be used for a.c.torque, which is zero. Hence these instruments cannot be used for a.c. The cost of these instruments is higher than that of moving iron instruments.The cost of these instruments is higher than that of moving iron instruments.
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Moving IronMoving Iron
Attraction TypeAttraction Type
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Repulsive Type:Repulsive Type:
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DynamoMeter TypeDynamoMeter Type
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Digital VoltmeterDigital Voltmeter
A digital voltmeter (DVM) displays the value of a.c. or d.c. voltage being measured directlyA digital voltmeter (DVM) displays the value of a.c. or d.c. voltage being measured directlyas discrete numerals in the decimal number system.as discrete numerals in the decimal number system.
Numerical readout of DVMs is advantageous since it eliminates observational errorsNumerical readout of DVMs is advantageous since it eliminates observational errorscommitted by operators.committed by operators.
The errors on account of parallax and approximations are entirely eliminated.The errors on account of parallax and approximations are entirely eliminated.
The use of digital voltmeters increases tile speed with which readings can be taken.The use of digital voltmeters increases tile speed with which readings can be taken.
A digital voltmeter is a versatile and accurate voltmeter, which has many laboratoryA digital voltmeter is a versatile and accurate voltmeter, which has many laboratoryapplications.applications.
On account of developments in the integrated circuit (IC) technology, it has been possible toOn account of developments in the integrated circuit (IC) technology, it has been possible toreduce the size, power requirements and cost of digital voltmeters.reduce the size, power requirements and cost of digital voltmeters.
In fact, for the same accuracy, a digital voltmeter now is less costly than its analogIn fact, for the same accuracy, a digital voltmeter now is less costly than its analogcounterpart.counterpart.
The decrease in size of DVMs on account of use of ICs, the portability of the instruments hasThe decrease in size of DVMs on account of use of ICs, the portability of the instruments hasincreased.increased.
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Types:Types:
Ramp type DVMRamp type DVM
Integrating type DVMIntegrating type DVM
Potentiometric type DVMPotentiometric type DVM
Successive approximation type DVMSuccessive approximation type DVM
Continuous balance type DVMContinuous balance type DVM
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Ramp type DVMRamp type DVM
Sample
Gate
Gate Counter
D
I
S
P
L
A
Y
Ranging and Attenuator
Ranging and Attenuator
Clock
Oscillator
Input
Voltage
Input
Comparator
Ground
Comparator
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Integrating type DVMIntegrating type DVM
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Potentiometric type DVMPotentiometric type DVM
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WATTMETERWATTMETER
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Three phase WattmeterThree phase Wattmeter
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Instrument TransformerInstrument Transformer