me 2304 engg metrology qn bank

8/10/2019 ME 2304 Engg Metrology Qn Bank

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ME 2304 Engg Metrology & Measurements Question Bank

(Approved by AICTE, Affiliated to Anna University)

DEPARTMENT OF MECHANICAL ENGINEERING

Prepared by,

C.Antony Vasantha Kumar

Department of Mechanical Engg

Question Bank

ME 2304ENINEERING METROLOGY & MEASUREMENTS


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TWO MARK QUESTIONS WITH ANSWERS


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UNIT I

1.

What is Range of measurement?:

The physical variables that are measured between two values. One is the higher calibration

value H , and the other is Lower value L, The difference between H, and L, is called range.

2.

What is Resolution?

The minimum value of the input signal is required to cause an appreciable change in the output

known as resolution.

3.

Define: Measurand.

Measurand is the physical quantity or property like length, diameter, and angle to be measured.

4.

Give any four methods of measurement

1. Direct method.

2. Indirect method.

3. Comparison method.

4. Coincidence method.

5.

Define Actual size

Actual size = Size obtained through measurement with permissible error.

6.

Differentiate accuracy and Uncertainty with example.

Accuracy - Closeness to the true value.

Example: Measuring accuracy is 0.02mm for diameter 25mm.

Here the measurement true values lie between 24.98 to25.02 mm

Uncertanity about the true value = 0.02mm

7.

Differentiate between precision and accuracy.

Accuracy - The maximum amount by which the result differ from true value.

Precision - Degree of repetitiveness. If an instrument is not precise it will give different results

for the same dimension for the repeated readings.

8.

Define Repeatability:

The ability of the measuring instrument to repeat the same results g the act measurements forthe same quantity is known as repeatability.

9.

Classify the Absolute error.

The absolute error is classified into 1. True absolute error 2. Apparent absolute error

10.

What is Relative error.


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Relative error is defined as the results of the absolute error and the, value of comparison used

for calculation of that absolute error. The comparison may be true value or conventional true

value or arithmetic rnean for series of measurement.

11.

Classify the errors

The errors can be classified into

1. Static errors - Reading errors

- Characteristic errors,

- Environmental errors

2. Loading errors 3. Dynamic error

12.

What is the basic Principle of measurement:

It is the physical phenomenon utilized in the measurement. If energy kind of quantity measured,

there must be a unit to measure it. So this will give the quantity to be measured in number ofthat unit.

13.

What are the important elements of measurements?

The important elements of a measurement is

I . Measurand 2. Reference 3. Comparator

14.

What is LEGAL METROLOGY

Legal metrology is part of Metrology and it is directed by a National Organisation which is called

"Notional service of Legal Metrology". The main objective is to, maintain uniformity of

measurement in a particular country.

15.

Define True size:

True size is Theoretical size of a dimension

16.

Differentiate between sensitivity and range with suitable example.

Example: A Instrument have a scale reading of 0.01mm to 100mm.

Here, the sensitivity of the instrument is 0.0lmm i.e. the minimum value in the scale by

which the instrument can read. The range is 0.01 to 100mm i.e. the minimum to maximum value

by which the instrument can read.

17.

Deflne system error and correction.

Error: The deviation between the results of measured value to the actual value.

Correction: The numerical value which should be added to the measured value to get the

correct result.

18.

Give classification of measuring instruments.

1. Angle measuring Instruments.


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2. Length measuring Instruments.

3. Instruments for surface finish.

4. Instruments for deviations.

19.

Define Span:

The algebraic difference between higher calibration values to lower calibration value.

Example: In a measurement of temperature higher value is 200*C and lower value is 150C

means span = 200 - 150 = 50C

20.

What is Response time:

The time at which the instrument begins its response for a change measured quantity.

UNIT II

1.

What are the considerations while manufacturing the slip gauges?

The following additional operations are carried out to obtain the necessary qualities in

slip gauges during manufacture.

1. First the approximate size of slip gauges is done by preliminary operations.

2. The blocks are hardened and wear resistant by a special heat treatment process.

3. To stabilize the whole life of blocks, seasoning process is done.

4. The approximate required dimension is done by a final grinding process.

2.

What are the various types of linear measuring instruments?

The various devices used for measuring the linear measurements are

i.Vernier calipers ii. Micrometers iii. Slip gauge or gauge blocks iv. Comparator

3.

List out any four angular measuring instrument used in metrology

(i) Angle gauges (ii) Divided scales (iii) Sine bar with slip gauges (iv) Autocollimator (v) Angle

dekkor.

4.

What is comparator?

Comparators are one form of linear measurement device which is quick and more convenient

for checking large number of identical dimensions.

5.

Classify the comparator according to the principles used for obtaining magnification.

The common types are: (i) Mechanical comparators. (ii) Electrical comparators. (iii) Optical

comparators. (iv) Pneumatic comparators.

6.

How the mechanical comparator works?

The method of magnifying small movement of the indicator in all mechanical comparators are

effected by means of levers, gear trains or a combination of these elements.

7.

State the best example of a mechanical comparator.


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A dial indicator or dial gauge is used as a mechanical comparator.

8.

Define least count and mention the least count of a mechanical comparator.

Least count. - The least value that can be measured by using any measuring instrument known

as least count. Least count of a mechanical comparator is 0.0 1 mm.

9.

State any four advantages of reed type mechanical comparator.

(i) It is usually robust, compact and easy to handle.

(ii) There is no external supply such as electricity, air required.

(iii) It has very simple mechanism and is cheaper when compared to other types.

(iv) It is suitable for ordinary workshop and also easily portable.

10.

Mention any two disadvantages of reed type mechanical comparator.

(i) Accuracv of the comparator mainly depends on the accuracy of the rack and pinion

arrangement. Any slackness will reduce accuracy.(ii) It has more moving parts and hence friction is more and accuracy is less.

11.

On what basis the transducer works?

An iron armature is provided in between two coils held by a leaf spring at one end. The other

end is supported against a plunger. The two coils act as two arms of an A.C. wheat stone bridge

circuit

12.

How is the accuracy of an electrical comparator checked?

To check the accuracy of a given specimen or work, first a standard specimen is placed under

the plunger. After this, the resistance of wheat stone bridge is adjusted that the scale reading

shows zero.

Then the specimen is removed. Now, the work is introduced under the plunger

13.

State the working principle of an electronic comparator.

In electronic comparator, transducer induction or the principle of application of frequency

modulation or radio oscillation is followed.

14.

State the principle of interferometry.

Mutual interference occurs when two rays with same wavelength meet at same point. The

nature of interference will depend upon the phases of the two waves at their meeting point.

15.

Define plug gauges.

Plug gauges are limit gauges which have two ends namely GO end and NOGO end. Both

these ends are hardened and ground to perfect size. Go end will be equal to the lower limit size

of the hole and NOGO end will be equal to the upper

16.

State Taylors principle.


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Taylors principle states that GO gauge should check all related dimensions

simultaneously, whereas NOGO gauges should check only one dimension at a time.

17.

What do you mean by autocollimator?

Autocollimator is an optical instrument used for the measurement of small angular

differences, changes or deflection, plane surface inspection and so on.

18.

State the types of pneumatic comparator.

Pneumatic comparator has been classified into two types. They are: 1. Flow type and

2.Back pressure type.

19.

What do you mean by snap gauges?

These gauges are also called as gap gauges and are used to check the external

dimensions. There are different types are snap gauges available 1. Progressive type and 2.

Double ended type.20.

Define wringing of slip gauges.

Wringing is the property of measuring faces of a gauge block of adhering by sliding or

pressing the gauge against the measuring faces of other gauge block or the reference faces or

datum surfaces.

UNIT III

1.

Name the various types of pitch errors found in screw?

(i) Progressive error (ii) Drunken error (iii) Periodic error (iv) Irregular errors.2.

Name the various methods of measuring the minor diameter of the thread.

(i) Using taper parallels. (ii) Using rollers and slip gauges.

3.

Name the various methods for measuring effective diameter.

(i) One wire method (ii) Two wire method (iii) Three wire method.

4.

What is best size of wire?

Best size of wire is a wire of such diameter that it makes contact with the flanks of the

thread on the pitch line.

5.

Define. Drunken thread

This is one, having erratic pitch, in which the advance Of the helix is irregular in one

complete revolution of thread.

6.

What is the effect of flank angle error?

Errors in the flank cause a virtual increase in the effective diameter of a bolt and

decrease in that, of nut.


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7.

What are the applications of toolmaker's microscope?

(i) Linear measurement (ii) Measurement of pitch of the screw (iii) Measurement'of thread

angle.

8.

Define: Periodic error.

The periodic error repeats itself at equal intervals along the thread.

9.

Define: Module

Module= pitch circle diameter/ number of teeth

10.

Define: Lead angle

It is the angle between the tangent to the helix and plane perpendicular to the axis of cylinder.

11.

Name four gear errors.

(i) Pitch error (iii) Alignment error (ii) Composite error (iv) Thickness error

12.

Define : constant chordConstant chord is the chord joining those points, or opposite Aaces of the tooth.

13.

Define fullness and emptiness in form factor.

Degree of fullness (K)= area of metal /Area of enveloping rectangle

Degree of emptiness = 1 - K

14.

What are the stylus probe instruments?

a) Profilo meter b) Taylor Hobson Talysurf c) Tomlinson surface meter

15.

Define: Straightness of a line in two planes.

A line is said to be straight over a given length, of the variation of the distance of its points from

two planes perpendicular to each other and parallel to the direction of a line remaining within

the specified tolerance limits.

16.

Define: Roundness. Name the four measurement of roundness.

It is a surface of revolution where all the surfaces intersected 'by any plane perpendicular to a

common axis in case of, cylinder and cone. a. Heart square circle. b. Minimum radial separation

circle. c. Maximum inscribed circle. d. Minimum circumscribed circle.

17.

Define : lay

Lay: -Direction of the 'predominate surface pattern'

18.

What is runout?

Run out. -Total range of reading of a fixed indicate Or with the contact points applied to a

Surface rotated, without axial movement, about 3 fixed axis.

19.

What are the two methods used in measuring radius of concave surface.

a) Edges are well defined. b) Edges are rounded up.


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20.

What are the methods used for evaluating the surface finish?

a) Peak to valley height method. b)The average roughness method. c) Form factor method.

UNIT IV

1.

What is interferometer?

Interferometer is optical instruments used for measuring flatness and determining the lengths

of slip gauges by direct reference to the wavelength of light.

2.

Name the different types of interferometer?

1) NPL flatness interferometer 2)Michelson interferometer 3) Laser interferometer 4) Zesis

gauge block interferometer.

3.

What is crest and trough?

The light is a form of energy being propagated by electromagnetic waves, which is a sine curve.

The high point of the wave is called crust and the low Point is called is trough.

4.

What is meant by alignment test on machine tools?

The alignment test is carried out to check the grade of manufacturing accuracy of the machine

tool.

5.

Distinguish between geometrical test and practical test on a machine tool

The alignment test is carried out to check the grade of manufacturing accuracy of the

machine tool. Performance test consist of checking the accuracy of the finished component.

Alignment test consist of checking the relationship between various machine elements whenthe machine tool is idle. Performance test consists of preparing the actual test jobs on the

machine and checking the accuracy of the jobs produced.

6.

Write the various tests conducted on any machine tools

1.Test for level of installation of machine tool in horizontal and vertical planes.

2.Test for flatness of machine bed and for straightness and parallelism of bed ways on bearing

surface.

3.Test for perpendicularity of guide ways to other guide ways.

4.Test for true running of the main spindle and its axial movements.

7.

Why the laser is used in alignment testing?

The alignment tests can be carried out over greater distances and to a greater degree of

accuracy using laser equipment. Laser equipment produces real straight line, whereas an

alignment telescope provides a, imaginary line that cannot be seen in space.

8.

Classify the machine tool test.


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(ii) Elimination of need for precise part location.

(iii) Integrated automation of dimensional verification (iv) Defect detection.

17.

Define grayscale analysis.

In these techniques, discrete areas or windows are formed around only the portions of the

image to be inspected. For determining if brackets are present, high intensity lighting is

positioned. This type of discrete area analysis is a powerful tool and can be used for inspection

of absence, correct part assembly, orientation, part, integrity, etc.

18.

Mention the advantages of CMM.

(i) The inspection rate is increased.

(ii) Accuracy is reduced.

(iii) Operator's error can be minimized. Skill of the operator is reduced.

(iv) Reduction in calculating, recording and set up time.(iv) No need of GO/NOGO gauges.

(vi) Reduction of scrap and good part rejection.

19.

Describe the features of a flexible inspection system.

(i) A powerful computer serves as a real time processor to handle part dimensional data and as a

multi 'programming system to perform such tasks as manufacturing process control.

(ii) The terminal provides interactive communication with personnel Computer where the

programmes are stored.

(iii) Input devices microprocessor based gauges and other inspection devices are used in CMM.

20.

Explain briefly the three important fields of machine vision system

Inspection: t is the ability of an automated vision system to recognize well-defined pattern and if

these pattern match these stored in the system makes machine vision ideal for inspection of

raw materials, parts, assemblies etc.

Part identification: It is the ability of part recognition provides positive identifications of an

object for decision-making purposes.

Guidance and Control. Machine vision systems are used to provide sensor feedback for real time

guidance.

UNIT V

1.

What are load cells?

Are devices for the measurement of force through indirect methods.

2.

Give the principle of hot wire anemometer


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When a fluid flows over a heated surface heat is transferred from the surface and so the

temperature reduces. The rate of reduction of temperature is related to flow rate.

3.

State any four inferential type of flowmeters

Venturi meter, orificemeter, rotameter, pitot tube.

4.

What is the principle involved in fluid expansion thermometer?

Change in pressure in the bulb is taken as an indication of the temperature.

5.

Mention the principle involved in bimetallic strip.

Is based on change in dimension

6.

What is thermocouple?

When two metals are joined together it will create an emf and it is primarily a function of the

junction temperature.

7.

What is thermopile?When thermocouples are connected in series it is called thermopile

8.

State the principle of proving ring.

When a steel ring is subjected to a force across its diameter, it deflects. This deflection is

proportional to the applied force when calibrated.

9.

Explain the principle of optical torsion meter.

Due to torque, an angular twist occurs on the shaft between its ends. This angle of twist is

measured by using optical means where in the angular defection of light rays is proportional to

twist and hence the torque.

10.

Give the classification of dynamometers.

Dynamometers are classified into the following types: 1. Absorption dynamomters, 2.

Driving dynamometers and 3. Transmission dynamometers.

11.

State the basic principle of obstruction meters.

When a fixed area flow restriction of some kind is placed in a pipe carrying the fluid whose

rate of flow is to be measured, the flow restriction causes a pressure drop which varies with the

flow rate. The pressure drop is measured using a differential pressure sensor and when

calibrated this pressure drop becomes a measure of flow rate.

12.

Mention the applications of Venturimeter.

a.

It is used where high pressure recovery is required.

b.

It can be used for measuring flow rates of water, wastes, gases and suspended solids.

c.

It can be used to measure high flow rates in pipes having diameters in a few meters.

13.

Give the main parts of Rotameter.


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a.

A tapered transparent glass tube graduated to read flow rate directly.

b.

A float whose density is greater than that of the flowing fluid. The float diameter is such

that it completely blocks the inlet of the tapered transparent glass tube.

14.

State the principle of Bimetallic strip.

All metals change in dimension, that is, expand or contract when there is a change in

temperature. The rate at which the change in dimension depends on the temperature

coefficient of expansion of the metal and this temperature coefficient of expansion is different

for different metals.

15.

Mention the materials employed in bimetallic strip.

1.

Nickel-iron alloys with chromium and manganese.

2.

Invar.

16.

Explain the principle of RTD.When an electric conductor is subject to a temperature change, the resistance of the

conductor changes. This change in resistance of the conductor becomes a measure of the change in

temperature when calibrated.

17.

Mention the application of RTD.

a.

It is usually used when temperature measurement is to be done from distance.

b.

Use in continuous monitoring situations.

18.

What do you mean by thermistors?

Thermistors are non-metallic resistors of ceramic material having negative coefficient of

resistance, used to measure temperature.

19.

Mention the type of thermistors.

a.

Bead type.

b.

Disc type.

c.

Washer type

d.

Rod type.

e.

Wafer type.

20.

Give the materials used in thermocouples.

a.

Chromel alumel.

b.

Iron-constantan.

c.

Rhodium-Iridium.

d.

Tungsten-Rhenium.


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16 MARK QUESTIONS WITH HINTS


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UNITI

1) Explain the various systematic and random errors in measurements?

CAUSES OF ERRORS

1. Calibration error:

These are caused due to the variation in the calibrated scale from its normal value.

2. Environment errors:

These errors are caused due to humidity condition, temperature, and altitude.

3. Assembly errors:

The assembly errors are due to 1.. Displaced scale i.e. incorrect fitting of the scale. 2.Nonuniform division of the scale. 3. Due to heni or distorted pointer.

4. Random errors:

There is no specific reason for causing of Random errors. It may naturally occur.

5. Systematic errors (or) Bias errors:

These type of errors caused due to repeated readings.

6. Chaotic errors:

Chaotic errors are caused due to vibrations, noises, and shocks.

2) What is the need of calibration? Explain the classification of various measuring methods.

1.

Direct comparison with Primary or Secondary Standard.2. Indirect comparison with a standard through calibration system.

3. Comparative method.4. Coincidence method.

5. Fundamental method.

6. Contact method.7. Transposition method.

8. Complementary method.

9. Deflection method.

3) Write detailed notes on:

(i) sensitivity


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(ii) Calibration

If a known input is given to the measurement system the output deviates from the given

input, the corrections are niade in the instrument and then the output is measured. This process

is called calibration.

(iii) Precision

Precision refers to the repeatability of a measuring process. It is connecting with the

performance of the instrument.

(iv) Interchangeability

Ability of the component to be interchangeable, like spare parts.

4) Define Repeatability, readability and Reproducibility with respect to measurement.

Repeatability: - Imperfections in mechanical systems can mean that during a Mechanical cycle, a

process does not stop at the same location, or move through the same spot each time. The variation

range is referred to as repeatability

Readabilityability of the measurement to be readable

Reproducibility- ability to be repeated when the measurement is conducted by same observerunder same conditions

5) Describe loading errors and environmental errors.

Loading means the measuring instrument always takes input from the signal source. Due to this,

the signal source will always be altered by the act of measurement known loading.

Example: If steam flow through the nozzle, it is very difficult to find the perfect flow rate.

This is called loading error

Every instrument is manufactured and calibrated at one place and it is used in some other place

where the environmental conditions such as temperature, pressure, and humidity are changes.

6) What are elements of a measuring system? How they affect accuracy and precision? How error due to

these elements is eliminated?

1) Measuring Instruments

2) Calibration Standards

3) Work piece

4) Person who is carrying out the measurement

5) Environment

The above said five elements composed into the acronym SWIPE.

Where,

S Standard

WWork pieceI Instrument

PPerson

E Environment

The factors affecting these five elements:

1. Standard: - Affected by Temperature, time, thermal expansion and elasticity.

2. Work piece: - Surface finish, cleanliness, supporting elements, and elastic properties.

3. Instrument: - Friction, error. Mechanical parts.

4. Person: - Ability to measure, training, cost estimation.

5. Environment: - Light. Temperature, Humidity.


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7) Explain with a neat sketch the generalized measurement system.

The various elements of measurement system are,

a. Variable sensing element.

b. Variable conversion element.

c. Data transmission element.

d. Data presentation element.

8) Briefly explain the random errors.

These types of errors occurs Randomly and reason for this type of errors cannot be

specified.

The source for this type of errors are

1. Displacement of level joints in the measuring instrument.

2. Small variation in the position of settings.

3. Reading scale error due to operator.

CAUSES OF ERRORS1. Calibration error:

These are caused due to the variation in the calibrated scale from its normal

value.

2. Environment errors:

These errors are caused due to humidity condition, temperature, and altitude.

3. Assembly errors:

The assembly errors are due to 1.. Displaced scale i.e. incorrect fitting of the

scale. 2. Non uniform division of the scale. 3. Due to heni or distorted pointer.

4. Random errors:

There is no specific reason for causing of Random errors. It may naturally occur.

5. Systematic errors (or) Bias errors:

These type of errors caused due to repeated readings.

6. Chaotic errors:

Chaotic errors are caused due to vibrations, noises, and shocks.

9) Write in detail the need of measurement.

NEED FOR MEASUREMENT

v To determine the true dimensions of a part.

v To increase our knowledge and understanding of the world.

v Needed for ensuring public health and human safety.

v To convert physical parameters into meaningful numbers.

v To test if the elements that constitute the system function as per the design.

v For evaluating the performance of a system.v For studying some basic laws of nature.

v To ensure interchangeability with a view to promoting mass production.

v To evaluate the response of the system to a particular point.

v Check the limitations of theory in actual situation.

v To establish the validity of design and for finding new data and new designs.

10) Distinguish clearly precision and accuracy.

Precision refers to the repeatability of a measuring process. It is connecting

with the performance of the instrument.


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Accuracy refers Closeness or conformity to the true value of the quantity under

measurement. Error refers the difference between true value and measured value is known as

measurement error.

UNIT-II

1) With neat sketch explain the construction and working principle of differential pneumatic

comparator.

The Soloflex Back Pressure System uses an orifice with the venturi effect to measure air

flow. If the gas is not moving, the pressure on both sides of the orifice will be equal.

A Differential Back Pressure system uses a split flow channel, one flow goes to the gauge

head, the other goes to a zero offset valve

2) With neat diagram explain the mechanism of Mechanical comparator?

The mechanism of such an instrument is. illustrated in figure. The stem has rack teeth. A set of gears engage with the rack. The pointer is connected to a small pinion.

The small pinion is independently hinged. i.e. it is not connected to the stern. The vertical movement of the stem is transmitted to the pointer through a set of

gears. A spring gives a constant downward pressure to the stem.

3) What is auto collimator? With neat sketch explain the working principle of the same.


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Basic principle:

If a light source is placed in the flows of a collimating lens, it is

projected as a parallel beam of light.

If this beam is made to strike a plane reflector, kept normal to the

optical axis, it is reflected back along its own path and is brought to the same focus.

If the reflector is tilted through a small angle 0. Then the parallelbeam is deflected

twice the angle and is brought to focus in the same plane as the light source.

4) Explain the precautionary measures one shall follow at various stages of using slip gauges.

The following additional operations are carried out to obtain the necessary qualities in slip

gauges during manufacture.i. First the approximate size of slip gauges is done by preliminary

operations.

ii. The blocks are hardened and wear resistant by a special heat treatment

process.

iii. To stabilize the whole life of blocks, seasoning process is done.

iv. The approximate required dimension is done by a final grinding process.

v. To get the exact size of slip gauges, lapping operation is done.

vi. Comparison is made with grand master sets.

Calibration of slip gauges

Comparators are used to calibrate the slip gauges.

SLIP GAUGES ACCESSORIES:The application slip gauges can be increased by providing accessories to the slip gauges. The

various accessories are

v Measuring jaw

v Scriber and Centre point.

v Holder and base.

1. Measuring jaw:

It is available in two designs specially made for internal and external features.

2. Scriber and Centre point:

It is mainly formed for marking purpose.

3. Holder and base:

Holder is nothing but a holding device used to hold combination of slip gauges.

Base in designed for mounting the holder rigidly on its top surface.

5) Explain with a schematic sketch the working principle of solex pneumatic comparator.


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6) Describe the method of checking the angle of a taper plug gauge using rollers.

7) Explain the working principle of Angle dekkor.

This is also a type of auto-collimator.

v There is an illuminated scale in the focal plane of the collimating lens.

v This illuminated scale is projected as a parallel beam by the collimating lens

which after striking a reflector below the instrument is refocused by the lens in thefiled of view of the eyepiece.

v In the field of view of microscope, there is another datum scale fixed across the

center of screen.

v The reflected image of the illuminated scale is received at right angle to the fixed

scale as shown in fig.

v Thus the changes in angular position of the reflector in two planes are indicated

by changes in the point of intersection of the two scales

8) Describe with the help of a near sketch, a vernier bevel protractor.


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9) Describe an opto-mechanical comparator.

The Eden-Rolt Reed system uses a pointer attached to the end of two reeds.

One reed is pushed by a plunger, while the other is fixed.

As one reed moves relative to the other, the pointer that they are commonly attached to

will deflect.

10) Explain with a neat sketch the principle of Reed type mechanical comparator.

In this type of comparator, the linear movement of the plunger is specified by means of

read mechanism. The mechanism of this type is illustrated in fig.

A spring-loaded pointer is pivoted. Initially, the comparator is set with the help of a

known dimension eg. set of slip gauges as shown in fig.

UNIT-III

1) How to measure the pitch of the screw thread by using the tool makers microscope? Discuss in

detail.

The image is projected by a system of three prisms to a ground glass screen.

The measurements are made by means of cross lines engraved on the ground glassscreen.

The screen can be rotated through 3 60.

Different types of graduated screens and eyepieces are used.


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2) Describe the method of inspecting the profile of spur gear by using involute measuring machine.

In this method the gear is held on a mandrel and circular disc of same diameter as thebase circle of gear for the measurement is fixed on the mandrel.

After fixing the gear in the mandrel. The straight edge of the instrument is brought incontact with the base circle of he disc.

Now, the gear and disc are rotated and the edge moves over the disc without sleep. Thestylus moves over the tooth profile and the error is indicated on the dial gauge

3) How to check the composite errors of the gear by using Parkinson gear testing machine? Explain it in

detail?

4) Describe the two wire method of finding the effective diameter of screw threads.

The three-wire method is the accurate method.

In this method three wires of equal and precise diameter are placed in the groves at

opposite sides of the screw. In this one wire on one side and two on the other side are used. The wires either mayheld in hand or hung from a stand.

This method ensures the alignment of micrometer anvil faces parallel to the thread

axis.


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5) Describe the chordal thickness method using gear tooth vernier caliper.

6) Describe a gear tooth vernier caliper and explain its use for checking tooth thickness and depth oftooth.

In gear tooth vernier method the thickness is measured at the pitch line. Gear tooth thickness varies from the tip of the base circle of the tooth, and the

instrument is capable of measuring the thickness at a specified position on the tooth. The tooth vernier caliper consists of vernier scale and two perpendicular arms. In the two perpendicular arms one arm is used to measure the thickness and other

arm is used to measure the depth. Horizontal vernier scale reading gives chordal thickness (W) and vertical vernier

scale gives the chordal addendum. Finally the two values e compared.

The theoretical values of W and d can be found out by considering one toothin the gear and it can be verified.

7) Discuss the principle of operation of Tomlinson surface meter.

When measuring surface finish the body of the instrument is moved across the surface by

a screw rotation.

The vertical movement of the probe caused by the surface irregularities makes the

horizontal lapped cylinder to roll. This rolling of lapped cylinder causes the movement of the arm. So this movement is

induces the diamond scriber on smoked glass. Finally the movement of scriber together with horizontal movement produces a trace

on the smoked glass plate and this trace is magnified by an optical projector.


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8) Explain the methods to analyse surface finish.

Analysis of surface finish

The analysis of surface finish being carried out by1. The average roughness method.

2. Peak to valley height method

3. From factorAverage roughness measurement:

The assessment of average roughness is carried out by

a Centre line average (CLA).b Root mean square (RMS)

c Ten point method

9) Describe a method to measure roundness with a neat sketch.

The V block is placed on surface plate and the work to be checked is placed upon it. A diameter indicator is fixed in a stand and its feeler made to rest against the surfaceof the work. The work is rotated to measure the rise on fall of the work piece.

For determining the number of lobes on the work piece, the work piece is first testedin a 60 V-Block and then in a 90 V-Block. The number of lobes is then equal to the number of times the indicator pointerdeflects through 360 rotation of the work piece.

10) Explain with a neat sketch the instrument to measure the minor diameter of the screw thread.

The Minor diameter of internal threads are measured by

1. Using taper parallels

2. Using Rollers.


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UNIT-IV

1) With neat sketch explain the various types of CMM based on its construction.

(i)Cantilever type: -

The cantilever type is very easy to load and unload, but mechanical error

takes place because of sag or deflection in Y-axis.(ii) Bridge type: - Bridge type is more difficult to load but less sensitive to mechanical errors.

(iii) Horizontal boring Mill type: -

This is best suited for large heavy work pieces.

2) Explain the construction and working principle of laser interferometer with neat diagram?

This

interferometer usescube corner reflectors which reflect light parallel to its angle of incidence. Beam splitter

B2 optically separates the frequency J which alone is sent to the movable cube corner

reflector. The second frequency from B2 is sent to a fixed reflector which then rejoins f1 at the

beam splitter B2 to produce alternate light and dark interference flicker at about 2 Megacycles per second. Now if the movable reflector moves, then the returning beam

frequency Doppler-shifted slightly up or down by f Thus the light beams moving towards photo detector P2 have frequencies f2 and

(f1 f 1) and P2 changes these frequencies into electrical signal. Photo detector P2 receive signal from beam splitter B2 and changes the referencebeam frequencies f1 and f2 into electrical signal. An AC amplifier A separates frequency. difference signal f2f1 and A2 separates

frequency difference signal.


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The pulse converter extracts i. one cycle per half wavelength of motion. The up-

down pulses are counted electronically and displayed in analog or digital form.3) Explain the various geometrical tests that are to be done to get a better accuracy in the machine tool?

TYPE OF GEOMETRICAL CHECKS ON MACHINE TOOLS .

Different types of geometrical tests conducted on machine tools are as follows:

1. Straightness.2. Flatness.

3. Parallelism, equi-distance and coincidence.

4. Rectilinear movements or squareness of straight line and plane.

5. Rotations.Main spindle is to be tested for

1) Out of round.

2) Eccentricity3) Radial throw of an axis.

4) Run out

5) Periodical axial slip

6) Camming

4) Discuss the various alignment test conducted on machine tool?

The accuracy of manufactured parts depends on the accuracy of machine tools. The quality of work piece depends on Rigidity and stiffness of machine tool and its

components. Alignment of various components in relation to one another Quality and accuracy of

driving mechanism and control devices. It can be classified into

1. Static tests2. Dynamic tests.

Static tests: If the alignment of the components of the machine tool are checked under staticconditions then the test are called static test.

Dynamic tests: If the alignment tests are carried out under dynamic loading condition. Theaccuracy of machine tools which cut metal by removing chips is tested by two types

of test namely.

1. Geometrical tests

2. Practical tests.

Geometrical tests:

In this test, dimensions of components, position of components and displacement

of component relative to one another is checked.Practical tests:

In these test, test pieces are machined in the machines. The test pieces must be

appropriate to the fundamental purpose for which the machine has been designed.

5) Write the uses of laser in alignment testing of machine tool.

The alignment tests can be carried out over greater distances and to a greaterdegree of accuracy using laser equipment. Laser equipment produces real straight line, whereas an alignment telescope

provides an imaginary line that cannot be seen in space.


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This is important when it is necessary to check number of components to a

predetermined straight line. Particularly if they are spaced relatively long

distances apart, as in aircraft production and in shipbuilding. Laser equipment can also be used for checking flatness of machined surface

by direct displacement. By using are optical square in conjunction with laser

equipment squareness can be checked with reference to the laser base line 6) Sketch and describe the optical system of a laser interferometer.

(a) Beam splitter

b) Beam benders

c) Retro reflectors

7) Discuss the principle of working of Michelson Interferometer.

When the reference beam reflected from the fixed mirror and the beam reflected from the

moving mirror rejoin at the beam splitter, they alternately reinforce and cancel each other as the

mirror moves Thus each cycle of intensity at the eye represents /2 of mirror travel.

8) Discuss the working principle of twyman green interferometer.

The Twyman-Green interferometer is used as a polarizing interferometer withvariable amplitude balancing between sample and reference waves.

For an exact measurement of the test surface, the instrument error can be determinedby an absolute measurement. This error is compensated by storing the same in microprocessorsystem and subtracting from the measurement of the test surface.

It has following advantages

1. It permits testing of surface with wide varying reflectivity.

2. It avoids undesirable feed back of light reflected of the tested surface and theinstrument optics.

3. It enables utilization of the maximum available energy.

4. Polarisation permits phase variation to be effected with the necessary precision.


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9) Explain the method to measure the distance between two holes using CMM

CMM is used for measuring the distance between two holes. The work piece is clamped to the worktable and aligned for three measuring slides x,y and z.

The measuring head provides a taper probe tip which is seated in first datum hole

and the position of probe digital read out is set to zero. The probe is then moved to successive holes, the read out represent the co-ordinate

part print hole location with respect to the datum hole. Automatic recording and data processing units are provided to carry out complexgeometric and statistical analysis.

Special co-ordinate measuring machines are provided both linear and rotary axes.

This can measure various features of parts like cone, cylinder and hemisphere.

10) Explain computer aided inspection by relating it with an application.

UNIT-V

1) How to measure the power by using rope brake dynamometer? Explain with a neat diagram

The main parts are two wooden blocks, a lever arm and a counter weight arrangement.

When the pulley rotates it tends to rotate the wooden blocks also in the same direction. This is

due to friction between the pulleys and blocks.

Due to the appropriate weight at the end of the arm, this can be prevented and is equilibrium in

position.


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2) Explain proven ring to measure force.

It contains a steel ring. When the steel ring is subjected to force its dimension chages.

The change in dimension is calibrated in such a way that it is proportional to the applied

force.

The main parts are A steel ring attached with external bosses and a precision

micrometer,

3) With neat sketch explain the construction and working principle of bimetallic strip.

All metals change in dimension that is expand or conract when there is a change in temperature.

The rate of change depends on the temperature coefficient of expansion.

A bimetallic strip is made of two thin strips of metals with different coefficient of thermal

expansion.

The two metals are joined by means of brazing or welding.

The deflection is linear and can be related to temperature change.

Metals used are Brass, Invar, Chromium and manganese.

4) List the advantages of temperature measurement by using the resistance thermometer.

Simple in construction.

Accurate in measurement.

Average temperature measurement is possible.

Easy to install.

Wide range of measuring equipments is available.

Easy reproducibility.

5) Explain with neat diagram the purpose and operating principle of a venturimeter.

Principle:

When venture meter is placed in a pipe carrying the fluid whose rate of flow is to be

measured, a pressure drop occurs between the entrance and throat of the

venturimeter. The pressure drop is measured using the pressure sensor.

Venturimeter has three sections namely convergent, throat and dicergent.

6) What are rotameters? Explain its principle of working.

Main parts are:

A tapered glass tube.

A float whose density is greater than that of the fluid.


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Principle of operation,

When the float which blocks the fluid passage rises due to increase in pressure of the

fluid, annular space is created. This space is concentric opening through which fluid

passes.

At one point the float becomes stationary, the height at which the float stays is to be

measured, which when calibrated proportional to the rate of flow.

7) Explain the working principle of a Mechanical torsion meter.


When a shaft is connected between a driving engine and driven load, a twist occurs which is

then calibrated in terms of torque. The angle of twist is measured using stroboscope.

Limitations,

Poor accuracy

Sensitivity is reduced.

Used only on shafts rotating at constant speed.

8) What are thermo couples? State its applications.


It is based on the principle of seeback effect. It states that when two conductors A and B

are joined together to form a junction and this junction is heated to higher temperature with respect to

free end an emf is induced.

The magnitude of the emf depends on the temperature.

9) Define pyrometer theory. Explain with a neat sketch any one pyrometer.

Pyrometry theory is given as E = x T

4

The three types of pyrometers are,

Total radiation pyrometers.

Infrared pyrometers.

Optical pyrometers.

10) Explain strain gauge load cell to measure force.


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The main parts are,

A cylinder made of steel, four strain gauges

Working,

When load is applied the dimension of the cylinder changes, which changes the resistance of the

strain gauge which in turn proportional to the applied force when calibrated. The strain gauges here are

mounted circumferentially at right angles to each other.

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me 2304 engg metrology qn bank

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