Measurement and Metrology Important Questions All units – Diploma N Scheme

Measurement and Metrology Important Questions

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We are adding  Diploma Measurements and metrology Important Questions and answers for N Scheme important Questions and answers for all Units – 3 Marks. Check the link below to download Diploma Measurements and metrology important questions and answers pdf & Diploma Measurements and metrology notes

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Department: Common to Mechanical and Automobile Department

Subject: 4020330, Measurements and Metrology                              Scheme: N

Unit 1 – Basic Concepts of Measurements

Three Marks

  1. What is Metrology?

Metrology is the science of measurement. Engineering Metrology is related to the measurement of lengths, angles and other quantities that are expressed in linear or angular terms

  1. Mention any three objectives of metrology.

The objectives of Metrology are

  1. To provide the required accuracy at minimum cost
  2. To minimize the cost of inspection
  3. To ensure the capability of measuring instruments
  4. To standardize the various measuring instruments
  5. To maintain the accuracy of the instrument by calibrating them periodically
  1. What are the systems of measurement?
  • P.S Systems
  • Metric Systems
  • S.I. System
  1. List the methods of Measurement.
    1. Linear measurement
    2. Angular measurement
    3. Direct method
    4. Indirect method
    5. Comparative method
    6. Coincidence method
    7. Contact method
  2. What are the standards of measurement?

There are two standards for measurement

  1. Line standard
  2. End standard
  1. What is end standard?

When the distance (length) is measured between two surfaces or faces it is called as End standard

  1. What is line standard?

When the distance (length) is measured between two lines it is called line standard

  1. What is the element of measurement?

There are five Basic  elements of measurement it is termed as SWIPE

  1. Standard (S)
  2. Workpiece (W)
  3. Instrument (I)
  4. Person (P)
  5. Environment (E)
  1. What is legal metrology?

Legal metrology is concerned with the regulations and legal requirements for the measuring instruments and methods of measurements

  1. What is precision?

Precision is the closeness of arrangement between independent test results obtained under specified conditions. Precision indicates the degree of responsibility in the measuring process

  1. What is accuracy?

Accuracy is the closeness of agreement between the measured value and its true value. The difference between the true value and the measured value is known as Error of Measurement

  1. What is sensitivity?

Sensitivity is defined as the ability of an instrument to detect small differences in the quantity being measured.

  1. What is calibration?

The process of periodically checking the measuring instruments and keeping the standards of the measuring instruments with high accuracy is called as calibration

  1. What is magnification?
  • Magnification is the process of measuring small difference in dimensions
  • In magnification process, the movement of the measuring tip in contact with the workpiece must be magnified.
  • Magnification may be achieved by mechanical, electrical, optical, pneumatic principle
  1. What is interchangeability?

Interchangeability is used in Mass production, In mass production, any part should assemble satisfactorily with any other mating part. Interchangeability is possible when common standards are established

  1. What is reliability?

Reliability is the ability of an instrument to perform function over a period of time

  1. Define Error.

Error in measurement is defined as the difference between measured value and true value

Error = Measured Value – True Value

  1. What are the sources of error?
    1. Calibration of the instrument
    2. Workpiece
    3. Operator’s skill
    4. Measuring arrangement
    5. Environmental condition
  1. What are the classifications of error?

Errors in measurement is classified based on nature sources mentioned below.They are

  1. Gross Error
  2. Systematic error
  3. Random or Environmental Error

Measurement and Metrology Important Questions

Unit 2 – Linear and Angular Measurements

  1. What are the Linear Measuring Instruments?

Linear Measuring instruments are used to measure the lengths, diameter, heights and thickness. This may be internal or external. In linear measuring instruments spaced lines are used for measurements.

  1. What are the angular measuring instruments?

The angle is a measurement that we can measure between the two lines which meet at one point. Angular measurements are playing a very crucial role in measurements. The best example is that the Ships and the Aeroplanes will navigate with the help of The precise angular directions of the landing area.

Bevel Protractor, Sine bar, Combination set,, angle gauges are used for angular measurement

  1. What is a caliper? Mention its types

Calipers are used to transfer the distance between the faces of a product to a scale or micrometer or vernier caliper. Clipers are meant for end measurements. They transfer end measurement to line measurement.

Calipers are classified into three major types. They are (i) Outside Caliper (ii) Inside Caliper (iii) Jenny Caliper

  1. What is a combination set?

Combination set is a set of steel rule, square head, protractor head and center head. Combination set is general used in layout and inspection head.

Steel Rule: Used for linear measurements

Square head: used for measuring Perpendicular and flatness measurements

Protractor head: Used for measuring angles

Center head: Used for finding the center line of cylindrical objects

  1. What is feeler gauge?

Feeler gauges are used for measuring the clearance between two mating parts. Feeler gauge consists of strips of sheet of different thickness. These strips are assembled together in a holder. Feeler gauges are mostly used in automobile sector.

  1. What is Pitch screw gauge?

Pitch screw gauges are used to measure the pitch of a thread. It consists of a number of threaded blades of different standard pitches. They are available for 50O AND 60O included thread angle.

  1. What is the least count of Vernier Caliper and Micrometer?

The least count in vernier caliper is defined as the difference between the values of a main scale division and vernier scale division.

Least Count (Vernier Caliper) = 1 Main Scale Division – 1 Vernier Scale Division

Least Count (Vernier Caliper) = 0.02mm

The Least Count in Scre gauge is the minimum distance that can be measured accurately by the instrument

Least count (Screw gauge) = Pitch / No. of thimble divisions

  1. What are the sources of error in micrometer?

The possible sources of Error in micrometer are

  1. The anvil surfaces are not flat
  2. The anvil surface are not parallel
  3. Zero error
  4. Applying too much pressure on the thimble
  5. Wear of anvil surfaces and ratchet mechanisms
  6. Mention the Indian Standard on Slip gauges?

The Indian standard on slip gauges are the slip gauges are made from high grade steel with coefficient of thermal expansion 11.5 x 106 per degree Celsius between 1O and 30OC

The commonly available slip gauges are M45, M87, M33 AND M112

  1. What is Bevel Protractor? Mention its Types

Bevel Protractor is one of the angle measuring instruments. Bevel protractor is used to measure the angle of a given surface or object. There are different types of Bevel protractor. They are (i) Vernier Bevel Protractor (ii) Universal Bevel Protractor (iii) Optical Bevel Protractor

  1. What is sine bar? Write its types
  • Sine bar is an angular measuring instrument
  • A sine bar consists of a steel bar and two rollers
  • Sine Bars used along with slip gauges for the measurement of angles.
  • Sine bars used to measure the angles of a given object or surface very accurately
  1. What is the principle of sine bar?

Sine bar is based on the laws of trigonometry. To set or find the angle, one roller of the sine bar is placed on the surface plates. The combination of slip gauges is inserted under the second roller.

Sin θ = Oppsite side (h) / Hypotenuse side (L)

Angle of the given object θ = sin -1 (h /L)

  1. What are the applications of Sine bar?
  • Locating any work to a given angle
  • Checking or measuring unknown angles
  • When the component is heavy size
  1. What is Autocollimator?

Autocollimator is an optical instrument and a special form of telescope. Autocollimator is used to measure smaller angle of differences, changes, deflections and plane surfaces.

  1. What is Comparator? Write its uses

Comparator is a precision instrument used to compare the component with a working standard. Slip gauges are generally used as working standards. Comparators are needed when identical parts are produced on a very large scale.

  1. Write the classification of Comparator.

Comparators are classified into the following types

  • Mechanical Comparator
  • Electrical & Electronic Comparator
  • Optical Comparator
  • Pneumatic Comparator
  • Electro Mechanical Comparator
  1. What are the advantages of Mechanical Comparator?

Advantages of Mechanical Comparator

  • They are cheaper compared to other types of comparator
  • They do not need external agency such as electricity or compressed air
  • They have linear scale
  • They are easy to handle
  1. What is Pneumatic comparator? List its types

A pneumatic comparator is a precision device operated using a pneumatic system or compressed air. Like other mechanical, optical, and electrical comparators, pneumatic comparators are also used to analyze the dimensional difference between the workpiece to be measured and the standard workpiece

Types:

  • Air flow or velocity type
  • Back pressure type

Unit 3 – Form Measurement

  1. What is a Screw thread?

A screw thread is a continuous helical groove of specified cross produced on the external or internal surface of a cylinder or a cone

  1. Mention the types of Screw threads.

The screw threads are grouped into two principal classes based on the form of thread

  • Vee threads
  • Transmission threads 
  1. Explain root of the srew thread

Root is the bottom of the groove between the sides of two adjacent threads

  1. What is a pitch of a screw thread?

The distance measured parallel to the axis from a point on a thread to the corresponding point on the next (adjacent) thread is called pitch of the thread

  1. Define major diameter.

Major diameter is the diameter of an imaginary co-axial cylinder which would touch the crests of an external thread or roots of an internal thread. Major diameter is also called external diameter or outside diameter

  1. What is a Effective diameter?

Effective diameter is the diameter of an imaginary co-axial cylinder which intersects the flanks of the threads such that the widths of the threads and widths of the spaces between the threads are equal, each being half the pitch

  1. What are the various elements of a screw thread?

The various elements of a screw thread are.

  • Major Diameter
  • Minor Diameter
  • Effective diameter
  • Pitch
  • Flank angles
  • Thread form
  1. Mention the methods of measuring major diameter of external method.

The methods of measuring major diameter of external method are

  • Using ordinary micrometer
  • Using bench micrometer
  1. Name the methods of measuring minor diameter of internal method.

The methods of measuring major diameter of external method are

  • Using taper parallels
  • Using rollers & slip gauges
  1. What is one wire method?

In one wire method, one wire is placed between two threads at one side and the anvil of the measuring micrometer contacts the crests on the other side.

  1. Explain two wire method

In this method the effective diameter of a screw thread is measured by placing two wires or rod of identical diameter. The wires of suitable sizes are placed between the standard and the micrometer anvils and the first micrometer reading is taken

  1. What is three wire method?

In three wire method, three wires of equal and precise diameter are placed in the thread groves at opposite sides of the screw and measuring the distance M over the outer surfaces of the wires with the micrometer.

  1. What is the purpose of tool makers microscope?

The tool makers microscope is used to determine many measurements such as Linear measurements, Pitch measurements, thread angle measurements, comparison between standard profile of thread forms, Pitch diameter measurement

The tools makers microscope is based on optical projection method

  1. Explain screw pitch gauge.

Screw pitch gauge is the simplest method of determining the pitch of thread. This type of gauge usually has adjustable anvils which are set the correct distance apart using setting plugs

  1. Mention the different methods of measurement of pitch.

The different methods of measurement of pitch are

  • Pitch measuring machine
  • Tool makers microscope
  • Screw pitch gauge
  1. What is a gear? Mention the types of gear.

Gears are the toothed wheels used for transmission of power or motion from one shaft to another shaft without slip.

Types of Gear

  • Spur gear
  • Helical gear
  • Bevel gear
  1. What is Pitch circle in gears?

In every pairs of gears in mesh, the two circles representing the two plain wheels in contact are always assumed to exist. Each of these circle is called as pitch circle.

  1. Explain addendum and dedendum in gears

Addendum

Addendum is the radial height of tooth from the pitch circle to the tip of the tooth

Dedendum

Dedendum is the radial depth of tooth from the pitch circle to the root of the tooth

  1. What is Diametral pitch?

Diametral pitch is the number of teeth per unit length of the pitch circle diameter

Diametral Pitch = Number of teeth / Pitch circle diameter = t / d

  1. Define Module.

Module is the linear distance in mm that each tooth of the dear would occupy, if the dear teeth were spaced along the pitch diameter

Module = Pitch circle diameter / Number of teeth = d/T

  1. What are the errors in a gear?

The errors in a gear are

  • Pitch error
  • Profile error
  • Composite error
  • Tooth thickness error
  • Cyclic error
  • Run out
  • Eccentricity
  • Tooth alignment error
  • Periodic error
  1. Mention the elements used to measure a gear

The elements used to gear are

  • Pitch
  • Runout
  • Profile
  • Backlash
  • Lead
  • Tooth thickness
  • Concentricity
  • Alignment
  1. What is Runout?

The eccentricity in the pitch circle is called Runout. This is measured by means of gear eccentricity tester.

  1. What is pitch error?

It is a source of gear noise and the type of noise depend upon how pitch errors are produced. Pitch error is the difference between actual and design pitch

  1. Explain profile error in gears.

Profile error is the maximum distance on the tooth profile form and the normal to the desing when two gears are having contact with each other at reference circle.

  1. What is Optical Projection method?

Optical projection method is one of the methods in profile measurement. In this method, the gear under test is magnified by optical lens and projected on the screen. It is then compared with master profile. This method is quick and suitable for checking the profile of small thin instrument gears.

  1. Explain Constant chord method.

Constant chord method is used for measuring tooth thickness. The constant chord method enables to employ one setting for all the gears having same pitch and pressure angle irrespective of the number of teeth.

  1. What is the purpose of Parkinson gear tester?

Parkinson’s gear tester is a testing device used to measure the variation in the center distance of two gears in mesh. It consists of a master gear and a gear to be tested. Both the gears are rotated, as the gears are rotated the center distance would vary.

Unit: 4, Advances in Metrology                               

  1. What is laser?

Laser is a device that emits light through a process of optical amplification based on the stimulated emission of electronic magnetic radiation

Laser stands for Laser Amplification by stimulated emission of Radiation

  1. What are the types of Laser?

There are four types of Laser

  1. Solid state laser
  2. Liquid laser
  3. Gas laser
  4. Semi-conductor laser
  1. Mention the advantages of Laser.
    1. More intensive than any other monochromatic source
    2. No moving parts
    3. Low power instruments
    4. More precise and accurate can prevail over long distances
    5. Wide dynamic range and high contrast.
  2. What are the applications of Laser?
    1. In manufacturing field, it is used for high quality cutting, drilling, welding surface treatment
    2. In medical field, it is used for surgery, kidney stone treatment, eye treatment, in dentistry for diagnosis
    3. In military field, it is used as target designation, for missile defense for blinding tropes.
  3. What are the parts of Laser telemetric system?

The parts of Laser telemetric system are

  1. Transmitter
  2. Receiver
  3. Processor electronics
  1. What are the advantages of laser telemetric system?
    1. High speed scanning is possible
    2. On-line gauging can be done
    3. Changes in dimensions can be quickly detected while the components are moving through the measurement region
    4. The output is available in digital form
  1. Explain Scanning laser gauge.

Scanner basically utilizes a transmitter, receiver and processor electronics.  A transmitting unit emits a laser beam that scans at a very high and known speed across the measuring range. Every object placed in the measuring field interrupts the laser beam and casts its shadow into the receiver.the difference between the shadow edges provides results to an accuracy of ±0.25µm for 10-50 mm diameter objects.

  1. What is Photo Diode array imaging?

In this method, shadow of stationary part is projected on a solid-state diode array image sensor. The system comprises of laser source, imaging optics, photodiode array and signal processor and display unit. For large parts, two arrays one for each edge are used.

  1. What is the purpose of diffraction pattern technique?

The purpose of diffraction pattern technique is used to measure small gaps and small diameter parts. In this method, a parallel coherent laser beam is diffracted by a small part and the resultant pattern is focused by a lens on a linear diode array.

  1. What is optical flat?

Optical flat is a circular piece of optical glass or fused quartz having its two plane faces flat and parallel and the surfaces are finished to an optical degree of flatness. Optical flats finished to an optical degree of flatness. Optical flats vary in size from 25mm diameter to about 300mm diameter.

  1. What are the uses of laser interferometry?
    1. Laser interferometry is used for optical components, calibration of slip gauges and in co-ordinate measuring machines
    2. Accurate measurement of linear dimensions is obtained
    3. Laser interferometry generates and compares the difference between two light wave.
  2. What is interferometer?

These are the instruments used for measuring linear dimensions. There are the different types of interferometer available. They are

  1. Standard interferometer
  2. Single beam interferometer
  3. AC interferometer
  4. Dual frequencies laser interferometer
  5. Michelson interferometer
  1. What is standard interferometer?

Standard interferometer is least expensive and can be used whenever possible. The measurement retroreflector for this interferometer is a cube corner. Displacement is measured between the interferometer and the cube corner.

  1. Explain single beam interferometer

Single beam interferometer has outgoing and returning beam superimposed on each other, giving the appearance of only one beam travelling between the interferometer and the retroreflector.

  1. Mention the components used in AC Laser interferometer.

The components used in AC Laser Interferometer are

  1. Two frequency Zeeman laser
  2. Beam splitter
  3. Fixed internal cube corner
  4. External cube corner
  5. Photo detector
  6. Amplifier
  7. Pulse convertor
  1. Explain Michelson Interferometer

The Michelson Interferometer consists of a monochromatic light source, a beam splitter and two mirrors. If relies on the principle of constructive and destructive interference as one mirror remains fixed and the other is moved.

  1. What is Twyman – Green interferometer

Twyman Green Michelson interferometer utilizes a pin hole source diaphragm and collimating lenses. In this way, all rays are rendered parallel to the central rays and thus all rays describe the same path

  1. Explain length bar measuring machine

Length bar measuring machine is also known as end bar measuring machine. This machine can be used to measure the length of the workpiece by direct comparison with a standard length bar. It consists of the following main parts

  1. Head stock
  2. Tail stock
  3. Micrometer screw
  4. Adjustable V –supports.
  1. Explain CMM.

CMM is Co-ordinate Measuring Machine has precise movements in three directions (x,y and z). the co-ordinates are controlled and measured by means of precision slides. The slides are equipped with linear measurements transducer which gives digital display. The transducer can also sense positive and negative direction.

  1. What are the types of CMM?
    1. Cantilever type
    2. Bridge type
    3. Horizontal bore mill
    4. Vertical bore mill
    5. Spherical co-ordinate type
  2. What are the advantages of CMM?

Using CMMM, the following advantages are observed,

  1. Accuracy is high
  2. The rate of inspection is fast
  3. The calculation time is less.
  4. Recording time is less
  5. Setup time is reduced.
  6. The inspection procedure is simplified
  7. The operator errors are reduced.
  1. What is computer controlled CMM?

The computer numerical control (CNC) system is used with CMM for the measurement of complicated parts. The inaccuracies are automatically corrected by the CNC.

  1. Explain three dimensional measuring machine

Three Dimensional machines are designed for 3-Dimensional calibration of certifiable accurate. Laser interferometers are provided as scales. A cooling system is incorporated to reduce the temperature rise when the machine is in operation.

  1. What are the limitations in Computer numerical controlled CNC?
    1. Calibration is to be done by means of a laser interferometer
    2. It is expensive
    3. Recalibration must be done when wear takes place.

Unit: 5, Measurement of Mechanical Parameters                                  

  1. What is force? List the different types of force measurement.

Force is directly proportional to the rate of change of momentum. Force is a vector quantity

Force may be measured by two methods. They are.

  • Direct force Measurement
  • Indirect force measurement
  1. What is direct force measurement?

In Direct force measurement, a direct comparison with a known gravitational force on a standard mass by means of balance is done

  1. Mention the different methods of Indirect Force measurement.

The direct force measurement is done by the following ways.

  • Equal arm balance
  • Unequal arm balance
  • Multiple level system
  • Pendulum scale and
  • Analytical Balance
  1. What is Indirect Force measurement?

In Indirect force measurement method, an indirect comparison by an calibrated transducer that senses by means of a gravitational weight is done.

  1. What are the different methods of Indirect force measurement?

The indirect force measurement is done by the following ways.

  • Electromagnetic Balance
  • Load cells
  • Accelerometers
  1. What is a Load cell? List the types of Load Cells

A load cell is a transducer that is used to convert a force into electrical signal. This conversion is indirect and happens in two stages. Through a mechanical arrangement the force being sensed is used to deform a strain gauge. The strain gauge converts deformation into electrical signals

Types of Load cells

  • Hydraulic load cell
  • Pneumatic load cell
  • Strain gauge load cell
  • Shear load cell
  • Capacitive load cell
  1. Explain strain gauge load cell

The strain gauge load cell is an electro-mechanical transducer which converts the changes in force/weight into changes in voltage. The change in voltage can be calibrated directly in terms of the force/load applied to the cell

  1. Mention the advantages of strain gauge load cell.
  • They are small and compact in size
  • They are well suited where an electrical output is desired.
  • Maintenance is free
  • Inexpensive

9. What is meant by Shear load cells?

Shear load cells are used to measure the load and bending moment. In this method, two cantilever beams are used. Both free ends of cantilever beams are bolted together.

  1. Explain Electronic Weighing system.

Electronic weighing system consists of load cell, signal conditioner, filter analog to digital converter (ADC), analog recorder display, printer, servo indicator and computer interface etc . it works with computer interface software.

  1. What is torque?

The force may exert a turning effort relative to any axis other than those intersecting the line of action. This turning effect is called torque.

  1. What is the purpose of dynamometer? Mention the types of dynamometers.

Dyanometers are devices used to measure cutting forces in machining operation.

Types of Dyanometers

  1. Absorption dynamometers
  2. Transmission dynamometers
  3. Driving dynamometers
  1. Explain DC Dynamometer

In DC Dynamometer, the DC machine acts as both motor and generator when it is coupled to the machine under test which is power generating machine. The power generated by the generator is dissipated in resistance grids or may be recovered as a useful power.

 

  1. What is Piezo electric sensors?

Piezoelectric sensors is based on sensor technology. Piezo electric sensors are used to measure the pressure, acceleration and also force using piezoelectric effect.

 

  1. Explain Force measurement and write types of flowmeters

In flow measurement, measures the rate of flow or quzntity of a moving fluid in an open or closed conduit

Types of flow meters

  1. Variable area meters
  2. Electromagnetic meters
  3. Turbine meters
  4. Ultrasonic meters
  5. Thermal flowmeters
  6. Vortex meters

 

16. What is Rotameter?

Rotameter is a flow measuring device. It consists of a vertical tapered tube with a float which is free to move up or down within the tube. The tube is made tapered so that there is a linear relationship between the flow rate and position of the float within the tube.

  1. Mention the advantages of Rotameter.
  • No external power of fuel
  • Low pressure drop is constant
  • Low cost
  • Good range
  • Usability for corrosive fluid
  • Good accuracy for low and medium flow rates
  1. Explain Electromagnetic flowmeter.

The electromagnetic flow meter works on the principle that when a conductor cuts a magnetic field a voltage is induced in the conductor. The magnitude of this voltage depends upon the strength of the magnetic field, the length of the conductor and speed at which the conductor cuts the magnetic field.

  1. What is hot wire anemometer?

Hotwire anemometer is a flow measuring device, used to measure the effect of the flowing fluid on a hot body. It consists of two thermocouples A and B connected in series to forma a thermopile

 

  1. Explain Ultrasonic flow meter.

In ultrasonic flow meters, the measurement of flow rate is determined by the variation in parameters of ultrasonic oscillations. There are two types of ultrasonic flowmeters

  1. Transit time method
  2. Doppler method

 

  1. Explain Doppler Flow meter.

In Doppler flow meter, an ultrasonic wave is projected at an angle through the pipe wall into the liquid by a transmitting crystal in a transducer mounted outside the pipe.

 

  1. Mention the advantages of Ultrasonic flowmeters

Does not impose additional resistance to the flow

Velocity / output relationship is linear

No moving parts

High repeatability

Non – contact measurement

  1. Explain Doppler Anemometer.

Laser Doppler anemometer is used for the measurement of instantaneous velocity of a gas or a liquid flowing in a glass walled channel. This instrument is the most recent advancement in the area of flow measurement especially measurement of high frequency turbulence fluctuations

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