2 marks question_of_ei

IMPORTANT QUESTIONS

Asst. Professor Mr. Jitendra Singh Bhadoriya ,Department of Electrical

& Electronics Engineering @ NRI Institute of Information Science &

Technology,Bhopal (M.P.) INDIA .Contact:Mob.+919039295053

Email:[email protected]

Electrical Instrumentation

2 Marks Questions

Question What is meant by measurement?

Answer Measurement is an act or the result of comparison between the

quantity and a predefined standard.

Question What are the 2 methods for measurement?

Answer Direct method and Indirect method.

Question Define Instrument.

Answer Instrument is defined as a device for determining the value or magnitude of a

quantity or variable.

Question List the types of instruments.

Answer The 3 types of instruments are Mechanical Instruments Electrical Instruments and Electronic Instruments.

Question Classify instruments based on their functions.

Answer

Indicating instruments

Integrating instruments

Recording instruments

Question Give the applications of measurement systems.

Answer The instruments and measurement systems are sued for

Monitoring of processes and operations. Control of processes and operations. Experimental engineering analysis.

Question Why calibration of instrument is important?

IMPORTANT QUESTIONS





Answer The calibration of all instruments is important since it affords the opportunity to

check the instrument against a known standard and subsequently to errors in

accuracy.

Question Explain the calibration procedure.

Answer Calibration procedure involves a comparison of the particular instrument with

Either. A primary standard A secondary standard with a higher accuracy than the instrument to be calibrated

or An instrument of known accuracy.

Question Define Calibration.

Answer It is the process by which comparing the instrument with a standard to correct

the accuracy.

Question Name the different essential torques in indicating instruments.

Answer Deflecting torque

Controlling torque

Damping torque

Question Name the types of instruments used for making voltmeter and ammeter.

Answer PMMC type

Moving iron type

Dynamometer type

Hot wire type

Electrostatic type

Induction type.

Question State the advantages of PMMC instruments

Answer Uniform scale.

No hysteresis loss

Very accurate

High efficiency.

Question State the disadvantages of PMMC instruments

IMPORTANT QUESTIONS





Answer Cannot be used for ac m/s

Some errors are caused by temperature variations.

Question State the applications of PMMC instruments

Answer m/s of dc voltage and

Current used in dc galvanometer.

Question How the range of instrument can be extended in PMMC instruments.

Answer In ammeter by connecting a shunt resister

In voltmeter by connecting a series resister.

Question State the advantages of Dynamometer type instruments

Answer Can be used for both dc and ac m/s. Free from hysteresis and eddy current errors.

Question State the advantages of Moving iron type instruments

Answer Less expensive Can be used for both dc and ac Reasonably accurate.

Question State the advantages of Hot wire type instruments

Answer Can be used for both dc and ac Unaffected by stray magnetic fields

Readings are independent of frequency and waveform

Question What are the constructional parts of dynamometer type wattmeter?

Answer Fixed coil Moving Coil

Current limiting resister Helical spring

Spindle attached with pointer Graduated scale

Question Write down the deflecting torque equation in dynamometer type

wattmeter.

Answer Td á VI CosÖ

Question State the disadvantages of Dynamometer type wattmeter

Answer Readings may be affected by stray magnetic fields.

At low power factor it causes error.

Question Name the errors caused in Dynamometer type wattmeter.

Answer Error due to pressure coil inductance

IMPORTANT QUESTIONS





Error due to pressure coil capacitance

Error due to methods of connection

Error due to stray magnetic fields

Error due to eddy current.

Question How the errors caused by pc inductance is compensated.

Answer By connecting a capacitor in parallel to the resister.

Question How the errors caused by methods of connection is compensated

Answer By using compensating coil.

Question Name the methods used for power measurement in three phase circuits.

Answer Single wattmeter method Two wattmeter method Three wattmeter method.

Question What are the special features to be incorporated for LPF wattmeter?

Answer Pressure coil circuit Compensation for Pressure coil current

Compensation for Pressure coil inductance.

Question Define Phantom loading.

Answer Method by which energizing the pressure coil circuit and current coil circuits

separately is called phantom loading.

Question State the use of phantom loading.

Answer Power loss is minimized.

Question Name the methods used in Wattmeter calibration.

Answer By comparing with std wattmeter.

By using voltmeter ammeter method.

By using Potentiometer.

Question What are the types of energy meters?

Answer Electrolytic meters

Motor meters.

Clock meters

Question Name the constructional parts of induction type energy meter.

Answer Current coil with series

IMPORTANT QUESTIONS





magnet Voltage coil with shunt

magnet Al disc

Braking magnet

Registering mechanism.

Question How voltage coil is connected in induction type energy meter.

Answer It is connected in parallel to supply and load.

Question How current coil is connected in induction type energy meter

Answer It is connected in series to the load

Question Why Al disc is used in induction type energy meter.

Answer Aluminum is a nonmagnetic metal.

Question What is the purpose of registering mechanism.

Answer It gives a valuable number proportional to the rotations.

Question What is the purpose of braking mechanism?

Answer It provides necessary braking torque.

Question Define creeping.

Answer Slow but continuous rotation of disc when pc is energized and cc is not

energized.

Question State the reason why holes are provided in Al disc.

Answer To avoid creeping holes are provided on both sides of Al disc.

Question What is the basic principle used in potentiometer

Answer In potentiometer the unknown emf is measured by comparing it with a std known

emf.

Question Name the potentiometer material used.

Answer In potentiometer the unknown emf is measured by comparing it with a std known

emf.

Question Name the potentiometer material used.

Answer German silver Manganin wire

Question Define standardization

Answer It is the process by which adjusting the current flows through the potentiometer

coil to make the voltage across the std cell is equal.

Question State the applications of potentiometer.

Answer Used for m/s of unknown emf Used for ammeter calibration Used for Voltmeter

calibration Used for wattmeter calibration

Question State the advantages of crompton potentiometer

IMPORTANT QUESTIONS





Answer More accurate Easy to adjust

Question What are the practical difficulties in ac potentiometers?

Answer More complicated Accuracy is seriously affected Difficulty is experienced in standardization.

Question Classify ac potentiometers

Answer Polar potentiometer Coordinate potentiometer.

Question How the phase angle is measured in polar type potentiometers.

Answer Polar potentiometer Coordinate potentiometer.

Question How the phase angle is measured in polar type potentiometers.

Answer It is measured from the position of phase shifter.

Question Name some ac potentiometers.

Answer Drysdale Tinsley potentiometer Gall Tinsley

potentiometer

Question State the advantages of ac potentiometers

Answer Can be used for m/s of both magnitude and phase angle Can be used for m/s of inductance of the coil. It is used in m/s of errors in CTS

Question State the applications of ac potentiometers

Answer M/s of self inductance.

Ammeter calibration

Voltmeter calibration Wattmeter calibration.

Question State the advantages of instrument transformers

Answer Used for extension of range Power loss is minimum

High voltage and currents can be measured.

Question State the disadvantage of instrument transformers

Answer Cannot be used for dc measurements.

Question What are the constructional parts of current transformer?

Answer Primary winding

Secondary winding

IMPORTANT QUESTIONS





Magnetic core.

Question Name the errors caused in current transformer.

Answer Ratio error

Phase angle error

Question Define ratio error.

Answer The ratio of energy component current and secondary current is known as

the ratio error.

Question How the phase angle error is created.

Answer It is mainly due to magnetizing component of excitation current

Question State the use of potential transformer.

Answer Used for m/s of high voltage Used for energizing relays and protective circuits.

Question Name the errors caused in potential transformer.

Answer Ratio error Phase angle error.

Question How the CT and PT are connected in the circuits.

Answer CT is connected in series and PT is connected in parallel.

Question Classify resistance

Answer Low resistance Medium resistance

High resistance

Question What is the range of medium resistance?

Answer Resistance of about 1 ohm to 100 kilo ohms is called medium resistance.

Question Name the methods used for low resistance measurement

Answer Ammeter – voltmeter method

Potentiometer method

Kelvin double bridge method

Ohm meter method.

Question Name the methods used for medium resistance measurement

Answer Ammeter – voltmeter method Substitution method Wheatstone bridge method

Carey foster bridge method

Question Where high resistance m/s is required?

Answer Insulation resistance of cables High resistance circuit elements

IMPORTANT QUESTIONS





Volume resistivity of a material Surface resistivity.

Question State the advantages of Wheatstone bridge method.

Answer Free from errors The balance is quit independent of source emf

Question State the advantages of Kelvin double bridge method.

Answer Errors owing to contact resistance, resistance of leads can be eliminated by using

this Kelvin double bridge

Question What are the constructional features of doctor ohmmeter?

Answer Permanent magnet

Current coil

Pressure coil

Battery

Pointer with graduated scale.

Question Define megger.

Answer The megger is an instrument used for the measurement of high

resistance and insulation resistance

Question Name the parts of megger.

It consists of a hand driven dc generator and a direct reading true ohm meter.

Answer What is the range of low resistance?

Question Resistance of about 1 ohm and under are included in this class.

Answer What is the range of medium resistance?

Question Resistance of 100 kilo ohms and above is usually termed as high resistance.

Answer What ranges of resistance can be measured by using doctor ohmmeter.

Question 0 to 500 micro ohms 0 to 5 milli ohms 0 to 50 milli ohms 0 to 500 milli ohms 0 to 5 ohms.

Answer How resistance is measured in direct deflection method.

Question The deflection of galvanometer connected in series with the resistance to be

Measured gives a measure of the insulation resistance.

Answer Classify the cables according to their sheathing.

Question Armoured cables Unarmoured cables.

IMPORTANT QUESTIONS





Answer Name the leads present in megger

Question Earth lead

Line lead

Guard lead.

Answer How resistance is measured by using ohm meter method.

Question Series ohm meter method Shunt ohm meter method.

Answer How resistance is measured in loss of charge method

Question In this method a capacitor is charged and discharged for a specific time period and

from this resistance is measured

Question State the balance equation used in bridge methods.

Answer The product of opposite branch resistances are equal

Question How the earth resistance is measured

Answer By using earth megger the value of surface earth resistance can be measured.

Question What are the basic elements of a generalized measurement system?

Answer The basic elements of a measurement system are primary sensing element,

variable conversion element, variable manipulation element, data transmission element and data presentation element.

Question Define the term precision

Answer Precision is the measure of the consistency or repeatability of a series of measurements.

Precision=1- Xi-X/Xi

Xi=the value of the ith

measurements. X=the average value of n measurements

Question What is the difference between accuracy and precision?

Answer Accuracy: It is the closeness with which an instrument reading approaches the

true value of the variable being measured.

Precision: It is the measure of reproducibility of the measurements.

Question List the different types of possible errors in measurements.

Answer The types of errors in measurements are systematic errors, Random errors and

gross errors

Question List any 4 static characteristics of a measuring system.

Answer The static characteristics of a measuring system are accuracy, sensitivity, resolution, precision, drift and dead zone.

Question What are the different types of standards?

IMPORTANT QUESTIONS





Answer The different types of standards are international standards, primary standards, secondary standards and working standards.

Question Define span.

Answer Span is defined as the algebraic difference the highest and lowest scale values of an instrument.

Question What is random error?

Answer Random error is an error due to unknown causes and observed when the magnitude and polarity of a measurement fluctuates in a unpredictable manner.

Question Define sensitivity of an instrument.

Answer Sensitivity of an instrument is a measure of the change in reading of an instrument for a given change in the measured quantity.

Question Define resolution of an instrument.

Answer Resolution of an instrument is the smallest change in the measured quantity that will produce a detectable change in the instrument reading.

Question Define limiting error

Answer In most instruments, the accuracy is guaranteed to be within a certain percentage

of full scale reading. Manufacturers have to specify the deviations from the nominal value of a particular quantity. The limits of these deviations from the

specified value are defined as limiting errors or guarantee errors. Limiting error = accuracy x full-scale value.

Question Define calibration

Answer Calibration is the process of checking the accuracy of instruments by comparing the instrument reading with a standard or against a similar meter of known

accuracy. It is also defined as marking the scale of an instrument.

Question Define fidelity

Answer Fidelity is defined as the degree to which a measurement system indicates changes in the measured quantity without any dynamic error.

Question Define dynamic error

Answer Dynamic error is defined as the difference between the true value of the

quantity changing with time and the value indicated by the measurement system if no static error is assumed. It is also called measurement error. It is

one the dynamic characteristics.

Question Define drift

Answer Drift is defined as slow variation of reading from a fixed value.

Question Define speed response

Answer Speed response is defined as the rapidity with which a measurement system responds to changes in measured quantity. It is one of the dynamic

characteristics of a measurement system.

Question Define reproducibility

IMPORTANT QUESTIONS





Answer Reproducibility is defined as the degree of closeness with which a given value may be repeatedly measured. It is specified in

terms of scale readings over a given period of time.

Question Define linearity

Answer The linearity is defined as the ability to reproduce the input characteristics

symmetrically and linearly

Question Define threshold

Answer Threshold is defined as the minimum value of the input at which the output starts changing/increasing from zero.

Question Define resolution

Answer Resolution is defined as the smallest increment of quantity being measured which can be detected with certainty being measured which can be detected with

certainty by an instrument.

Question Write the characteristics of the measurement system.

Answer Characteristics of measurement system is divided into two categories: i. Static characteristics

ii. Dynamic characteristics

Question Write the main static characteristics?

Answer The main static characteristics are: i. Accuracy

ii. Sensitivity

iii. Reproducibility

iv. Drift

v. Static error

vi. Dead zone

vii. Resolution

viii. Precision

ix. Repeatability

x. Stability

Question How controlling torque is produced?

Answer Using springs, & using control weight the controlling torque is produced

Question Why scale of gravity is non-uniform?

Answer The quantity is to measure is proportional to sin rather than in gravity control which is

not a uniform. Hence scale calibrated is not in uniform.

Question What are the different ways of producing damping torque in instruments?

Answer a) Air friction damping,

b) Fluid friction damping,

c) Eddy current damping.

IMPORTANT QUESTIONS





From-

Mr. Jitendra Singh Bhadoriya

Assistant Professor

Department of Electrical & Electronics Engineering

NIIST, Bhopal

2 marks question_of_ei

Engineering

Transcript of 2 marks question_of_ei