Unit 1 - Introduction-METROLOGY

ME 2304 Engineering Metrology & Measurement

What is What is metrology??

The most important parameter in metrology is the length. Metrology is divided into Industrial Metrology and Medical Metrology under consideration of its application and may be divided into metrology of length and Metrology of time under consideration of its quantity

It is the science of weights and measuresIt is the science of weights and measures

Refers primarily to the measurements of length, weight, time, etc.Refers primarily to the measurements of length, weight, time, etc.

It also includes other engineering measurements for the establishment of a flat, plane It also includes other engineering measurements for the establishment of a flat, plane reference surface reference surface

To ensuring these process meet specific degrees of both accuracy and precisionTo ensuring these process meet specific degrees of both accuracy and precision

ME 2304 Engineering Metrology & MeasurementMetrology is mainly concerned with:

Unit of measurement and their standards.Unit of measurement and their standards.

Errors of measurement.Errors of measurement.

Changing the units in the form of standards.Changing the units in the form of standards.

Ensuring the uniformity of measurements.Ensuring the uniformity of measurements.

New methods of measurement developing.New methods of measurement developing.

Analyzing this new methods and their accuracy.Analyzing this new methods and their accuracy.

Establishing uncertainty of measurement.Establishing uncertainty of measurement.

Gauges designing, manufacturing and testing.Gauges designing, manufacturing and testing.

Researching the causes of measuring errors.Researching the causes of measuring errors.

Industrial Inspection.Industrial Inspection.


FUNCTIONS OF METROLOGY

To ensure conservation of national standards.To ensure conservation of national standards.

Guarantee their accuracy by comparison with international standards.Guarantee their accuracy by comparison with international standards.

To organise training in this field.To organise training in this field.

Take part in the work of other National Organization.Take part in the work of other National Organization.

To impart proper accuracy to the secondary standards.To impart proper accuracy to the secondary standards.

Carry out Scientific and Technical work in the field of measurement.Carry out Scientific and Technical work in the field of measurement.

Regulate, supervise and control the manufacturer.Regulate, supervise and control the manufacturer.

Giving advice to repair of measuring instruments.Giving advice to repair of measuring instruments.

To inspect and to detect guilty of measurement.To inspect and to detect guilty of measurement.


NEED OF INSPECTION

To determine the fitness of new made materials, products Or component part and to To determine the fitness of new made materials, products Or component part and to compare the materials, products to the established standard.compare the materials, products to the established standard.

It is summarized as

To conforming the materials or products to the standard.To conforming the materials or products to the standard.

To avoid faulty product coming out.To avoid faulty product coming out.

To maintain the good relationship between customer and manufacturer.To maintain the good relationship between customer and manufacturer.

To meet the interchangeability of manufacturer.To meet the interchangeability of manufacturer.

To maintain the good quality.To maintain the good quality.

To take decision on the defective parts.To take decision on the defective parts.

To purchase good quality raw materials.To purchase good quality raw materials.

To reduce the scrap.To reduce the scrap.

BASIC CONCEPTS OF MEASUREMENTS:


1.Measurement is the outcome of an opinion formed by observers about some physical 1.Measurement is the outcome of an opinion formed by observers about some physical

quantity.quantity.

2. Measurement is an essential part of the development of technology.2. Measurement is an essential part of the development of technology.

3. Measurement is a complex of operations carried out by means of measuring instruments.3. Measurement is a complex of operations carried out by means of measuring instruments.

The means of Measurement classified as:

Standards — Used to reproduce the values of given quantity.

Fixed gauges — Used to check the dimensions, form.

Measuring instruments — Used to determine the measured values.


MeasurandMeasurand

ReferenceReference

ComparatorComparator

The important elements of a measurement is

11. Measurand:

It is a physical quantity or property (length, diameter, thickness, angle etc.).It is a physical quantity or property (length, diameter, thickness, angle etc.).

2. 2. Reference:

Reference is a physical quantity or property and comparisons are made by them.Reference is a physical quantity or property and comparisons are made by them.

3. 3. Comparator::

Comparing measurand with some other reference.Comparing measurand with some other reference.


NEED FOR MEASUREMENT

To determine the true dimensions of a part.

To increase our knowledge and understanding of the world.

Needed for ensuring public health and human safety.

To convert physical parameters into meaningful numbers.

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

For evaluating the performance of a system.

For studying some basic laws of nature.

To ensure interchangeability with a view to promoting mass production.

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

Check the limitations of theory in actual situation.

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


METHODS OF MEASUREMENT

1. Direct comparison with Primary or Secondary Standard.1. Direct comparison with Primary or Secondary Standard.

2. Indirect comparison with a standard through calibration system.2. Indirect comparison with a standard through calibration system.

3. Comparative method.3. Comparative method.

4. Coincidence method.4. Coincidence method.

5. Fundamental method.5. Fundamental method.

6. Contact method.6. Contact method.

7. Transposition method.7. Transposition method.

8. Complementary method.8. Complementary method.

9. Deflection method.9. Deflection method.


Measurements Standards:

→ English Speaking Countries (English System): Pound, Foot, Second

→ Metric System (SI – System International):Metric System (SI – System International): Kilogram, Meter, Second


Measurable ParametersWhat do we want to measure?

- Length or distance - Mass- Temperature - Elemental composition- Viscosity - Displacements or distortions- Time - Pressure- Forces - Stress- Strain - Friction- Resistance - Roughness- Depth - Intensity- etc.


NameName SymbolSymbol QuantityQuantity DefinitionDefinition

radian radian radrad Angle Angle The unit of angle is the angle subtended The unit of angle is the angle subtended at the centre of a circle by an arc of the at the centre of a circle by an arc of the circumference equal in length to the circumference equal in length to the radius of the circle. There are 2π radians radius of the circle. There are 2π radians in a circle. in a circle.

steradian steradian srsr Solid Solid angle angle

The unit of solid angle is the solid angle The unit of solid angle is the solid angle subtended at the centre of a sphere of subtended at the centre of a sphere of radius radius rr by a portion of the surface of the by a portion of the surface of the sphere having an area sphere having an area r2r2. There are 4π . There are 4π steradians on a sphere. steradians on a sphere.

Dimensionless UnitDimensionless Unit

ME 2304 Engineering Metrology & MeasurementNameName SymbolSymbol QuantityQuantity Expressed in base unitsExpressed in base units

HertzHertz HzHz FrequencyFrequency SS-1-1

NewtonNewton NN ForceForce Kg m sKg m s-1-1

JouleJoule JJ EnergyEnergy N m N m

WattWatt WW PowerPower J/sJ/s

PascalPascal PaPa Pressure, StressPressure, Stress N/mN/m22

LumenLumen LmLm Luminous fluxLuminous flux cd srcd sr

LuxLux LxLx I luminanceI luminance lm/mlm/m22

CoulombCoulomb CC Electric chargeElectric charge A sA s

VoltVolt VV Electric potential differenceElectric potential difference W/AW/A

OhmOhm ΩΩ Electric ResistanceElectric Resistance V/AV/A

FaradFarad FF Electric CapacitanceElectric Capacitance C/VC/V

WeberWeber WbWb Magnetic fluxMagnetic flux Kg mKg m22 s s-2-2 A A-1-1

TeslaTesla TT Magnetic Flux densityMagnetic Flux density Wb/mWb/m22

HenryHenry HH InductanceInductance Wb/AWb/A

SiemensSiemens SS Electric ConductanceElectric Conductance ΩΩ-1-1

BecquerelBecquerel BqBq RadioactivityRadioactivity ss-1-1

GrayGray GyGy Adsorbed Dose (of ionizing radiation)Adsorbed Dose (of ionizing radiation) J/kgJ/kg

SievertSievert SvSv Equivalent Dose (of ionizing Equivalent Dose (of ionizing radiation)radiation)

J/kgJ/kg

KatalKatal KatKat Catalytic activityCatalytic activity Mol/sMol/s

Degree of CelsiusDegree of Celsius 00CC Thermodynamic TemperatureThermodynamic Temperature KK


► ► Sensitivity:

Is the smallest difference in dimensions that the instrument can detect.

► ► Accuracy:

The ability of a measurement to match the actual value of the quantity being

measured.

► ► Precision:

The degree to which the instrument gives repeated measurements of the same

standard.


The difference between precision and accuracy can be shown by the spread of shooting of a tar-get (as shown in Diagram below):


CLASSIFICATION OF MEASURING INSTRUMENTS

ACCURACYACCURACY

PRECISION INSTRUMENTSPRECISION INSTRUMENTSEg : Micrometre,Vernier caliper etc.Eg : Micrometre,Vernier caliper etc.PRECISION INSTRUMENTSPRECISION INSTRUMENTSEg : Micrometre,Vernier caliper etc.Eg : Micrometre,Vernier caliper etc.

NON-PRECISION INSTRUMENTSNON-PRECISION INSTRUMENTSEg : Graduated rule,Scale etc.Eg : Graduated rule,Scale etc.NON-PRECISION INSTRUMENTSNON-PRECISION INSTRUMENTSEg : Graduated rule,Scale etc.Eg : Graduated rule,Scale etc.

MODEMODE

DIRECT READING DIRECT READING : : Used to determine the actual Used to determine the actual dimension and size.dimension and size.DIRECT READING DIRECT READING : : Used to determine the actual Used to determine the actual dimension and size.dimension and size.

IN DIRECT or TRANSFER TYPE IN DIRECT or TRANSFER TYPE : It transfer : It transfer the measurement from the work to a direct measuring the measurement from the work to a direct measuring instrument and a comparison is made. instrument and a comparison is made.

IN DIRECT or TRANSFER TYPE IN DIRECT or TRANSFER TYPE : It transfer : It transfer the measurement from the work to a direct measuring the measurement from the work to a direct measuring instrument and a comparison is made. instrument and a comparison is made.

TYPETYPELINE MEASURING DEVICESLINE MEASURING DEVICESLINE MEASURING DEVICESLINE MEASURING DEVICES

END MEASURING DEVICESEND MEASURING DEVICESEND MEASURING DEVICESEND MEASURING DEVICES


IMPORTANT TERMS IN MEASUREMENT

Calibration: If a known input is given to the measurement system the output deviates : If a known input is given to the measurement system the output deviates from the given input, the corrections are made in the instrument and then the output is from the given input, the corrections are made in the instrument and then the output is measured. This process is called calibration.measured. This process is called calibration.

Sensitivity:


True size and Actual size: True size mean theoretical size of a dimension which is True size mean theoretical size of a dimension which is free from errors. Actual size mean size obtained through measurement with permissible free from errors. Actual size mean size obtained through measurement with permissible error.error.

Range: The physical variables that are measured between two values. On is the higherThe physical variables that are measured between two values. On is the highercalibration value H, and the other is Lower value L. The difference between H and L, is calibration value H, and the other is Lower value L. The difference between H and L, is called range.called range. Span: The algebraic difference between higher calibration values to lower calibration The algebraic difference between higher calibration values to lower calibration value.value.Example: In a measurement of temperature higher value is 200°t and lower value is 150°C: In a measurement of temperature higher value is 200°t and lower value is 150°Cmeans span = 200 — 150 = 50°Cmeans span = 200 — 150 = 50°C

Resolution: The minimum value of the input signal is required to cause appreciable The minimum value of the input signal is required to cause appreciable change in the output known as resolution.change in the output known as resolution.

Threshold: The minimum value of input signal that is required to make a change or start The minimum value of input signal that is required to make a change or start from zero.from zero.

Back lash: The maximum distance through which one part of the instrument is moved The maximum distance through which one part of the instrument is moved without disturbing the other part.without disturbing the other part.


Uncertainty: The range about the measured value within the true value of the : The range about the measured value within the true value of the measured quantity is likely to lie at the stated level of confidencemeasured quantity is likely to lie at the stated level of confidence

Repeatability: - Imperfections in mechanical systems can mean that during a Mechanical - 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 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.time. The variation range is referred to as repeatability.

The accuracy of measurement depends uponThe accuracy of measurement depends upon

The ability of the operator.The ability of the operator.

Variation of temperatureVariation of temperature

Method adopted for measurementMethod adopted for measurement

Deformation of the instrumentDeformation of the instrument


ELEMENTS OF MEASURING SYSTEM:1) Measuring Instruments1) Measuring Instruments2) Calibration Standards2) Calibration Standards3) Work piece3) Work piece4) Person who is carrying out the measurement4) Person who is carrying out the measurement5) Environment5) EnvironmentThe above said five elements composed into the acronym “SWIPE”.The above said five elements composed into the acronym “SWIPE”.Where, S — StandardWhere, S — StandardW — Work pieceW — Work pieceI — InstrumentI — InstrumentP —PersonP —PersonE — EnvironmentE — EnvironmentThe factors affecting these five elements:1. Standard: - Affected by Temperature, time, thermal expansion and elasticity.1. Standard: - Affected by Temperature, time, thermal expansion and elasticity.2. Work piece: - Surface finish, cleanliness, supporting elements, and elastic 2. Work piece: - Surface finish, cleanliness, supporting elements, and elastic properties.properties.3. Instrument: - Friction, error. mechanical parts.3. Instrument: - Friction, error. mechanical parts.4. Person: - Ability to measure, training, cost estimation.4. Person: - Ability to measure, training, cost estimation.5. Environment: - Light. Temperature, Humidity.5. Environment: - Light. Temperature, Humidity.


ERRORS IN MEASUREMENT:

Error is the difference between the measured value and the true value.Error is the difference between the measured value and the true value.

Error in measurement = Measured Value — True valueError in measurement = Measured Value — True value

The errors in measurement can be expressed either as an absolute error or on relative The errors in measurement can be expressed either as an absolute error or on relative

error.error.

TYPES OF ERRORSTYPES OF ERRORS


1. Static error:It is from the physical nature of the various components of measuring system. It is from the physical nature of the various components of measuring system. The static errors due to environmental effect and other properties which influence The static errors due to environmental effect and other properties which influence the apparatus also reason for static errors.the apparatus also reason for static errors.a) Characteristic error:•The deviation of the output of the measuring system from the nominal The deviation of the output of the measuring system from the nominal performance specifications is called characteristic error.performance specifications is called characteristic error.•The linearity, repeatability, hysteresis and resolution are part of the characteristic The linearity, repeatability, hysteresis and resolution are part of the characteristic error.error.b) Reading errors:•It is exclusively applied to the read out device. The reading error describes the It is exclusively applied to the read out device. The reading error describes the factors parallax error and interpolation error.factors parallax error and interpolation error.•The use of mirror behind the readout indicator eliminates the occurrence of The use of mirror behind the readout indicator eliminates the occurrence of parallax error.parallax error.•Interpolation error is a reading error resulting from the inexact evaluation of the Interpolation error is a reading error resulting from the inexact evaluation of the position ‘ of index.position ‘ of index. (c) Environmental errors:•Every instrument is manufactured and calibrated at one place and it is used in Every instrument is manufactured and calibrated at one place and it is used in some other place where the environmental conditions such as temperature, some other place where the environmental conditions such as temperature, pressure, and humidity are changes.pressure, and humidity are changes.


2. Loading 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.3. Dynamic error:This is due to time variations in the measurand. The dynamic errors are caused by inertia, This is due to time variations in the measurand. The dynamic errors are caused by inertia, friction and clamping action. The dynamic errors are mainly classified intofriction and clamping action. The dynamic errors are mainly classified intoa) Systematic errors or Controllable errors.a) Systematic errors or Controllable errors.b) Random errors.b) Random errors.a) Systematic errors:a) Systematic errors:•The systematic are constant and similar in form. These are controllable in both their sense The systematic are constant and similar in form. These are controllable in both their sense and magnitude. The systematic errors are easily determined and reduced, hence these are and magnitude. The systematic errors are easily determined and reduced, hence these are also called as controllable errors.also called as controllable errors.Systematic errors includesSystematic errors includes1. Calibration errors.1. Calibration errors.2. Ambient or Atmospheric conditions2. Ambient or Atmospheric conditions3. Avoidable errors.3. Avoidable errors.4. Stylus pressure;4. Stylus pressure;


1. Calibration errors:Calibration is a process of giving a known input to the measurement system and also Calibration is a process of giving a known input to the measurement system and also taking necessary actions to see that the out of the measurement system matches with taking necessary actions to see that the out of the measurement system matches with its input. If the instrument is not calibrated, the instrument will show very high degree its input. If the instrument is not calibrated, the instrument will show very high degree of error.of error.

2. Ambient errors:This is due to variation in atmospheric conditions (Example: Pressure. Temperature This is due to variation in atmospheric conditions (Example: Pressure. Temperature and moisture) normally the instruments are calibrated at particular pressure and and moisture) normally the instruments are calibrated at particular pressure and temperatures.temperatures.Temperature will not be equal at all places. If the temperature and pressure varies, the Temperature will not be equal at all places. If the temperature and pressure varies, the ambient error will be formed. Standard temperature of 20°C and pressure of 760mm ambient error will be formed. Standard temperature of 20°C and pressure of 760mm Hg is taken as ambient condition.Hg is taken as ambient condition.

3. Avoidable errors:This type of error due to parallax, non-alignment of work piece centers, and improperThis type of error due to parallax, non-alignment of work piece centers, and improperlocation of measuring instrument. For example placing a thermometer in sunlight for location of measuring instrument. For example placing a thermometer in sunlight for measuring air temperature will cause the Instrument location error.measuring air temperature will cause the Instrument location error.


4. Stylus pressure:Whenever a component measured under pressure the deformation of the work piece andWhenever a component measured under pressure the deformation of the work piece andsurface deflection will occur. The pressure involved is generally small but this is sufficient surface deflection will occur. The pressure involved is generally small but this is sufficient to cause appreciable deformation on stylus and the work pieceto cause appreciable deformation on stylus and the work piece

b) Random errors:

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

specified.specified.

The source for this type of errors areThe source for this type of errors are

1. Displacement of level joints in the measuring instrument.1. Displacement of level joints in the measuring instrument.

2. Small variation in the position of settings.2. Small variation in the position of settings.

3. Reading scale error due to operator.3. Reading scale error due to operator.


CAUSES OF ERRORS

1. Calibration error: These are caused due to the variation in the calibrated scale from its 1. Calibration error: These are caused due to the variation in the calibrated scale from its

normal value.normal value.

2. Environment errors: These errors are caused due to humidity condition, temperature, and 2. Environment errors: These errors are caused due to humidity condition, temperature, and

altitude.altitude.

3. Assembly errors: The assembly errors are due to 1.. Displaced scale i.e. incorrect fitting of 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 distorted pointer.the scale. 2. Non-uniform division of the scale. 3. Due to distorted pointer.

4. Random errors: There is no specific reason for causing of Random errors. It may naturally 4. Random errors: There is no specific reason for causing of Random errors. It may naturally

occur.occur.

5. Systematic errors (or) Bias errors: These type of errors caused due to repeated readings.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.6. Chaotic errors: Chaotic errors are caused due to vibrations, noises, and shocks.

What is Microsystems Metrology

Measurement of physical dimensions of Microsystems or

structures that are at the dimension scale below our ability to

perceive without the help of measurements systems or instruments

Microsystems: IC, MEMS

Microstructures: Line widths, film thickness, surface structure and

roughness, step heights, particle size, atomic composition, defect

inspections, etc

Nanosystem metrology is emerging now!


Where Metrology at the Micro Level is Used

Precision engineering and measurements

Micron and nano manufacturing

Research and development

Calibration of instruments and standards


Basic Unit of LengthMeter is fundamental unit of length in the metric system.

The meter was originally defined as 1/10,000,000 of the distance between the equator and either pole; however, the original survey was inaccurate and the meter was later defined simply as the distance between two scratches on a bar made of a platinum-iridium alloy and kept at Sevres, France, near Paris. More recently, it has been defined as the distance light travels through a vacuum in 1/299,792,458 of a second. The meter is now the legal standard of length for most of the world, other standards, such as the yard, being defined in terms of the meter.


SI Base Units

Basic Unit of Mass

Kilogram is fundamental unit of mass is equal to the mass of the

international prototype kilogram (a platinum-iridium cylinder) kept

at the Bureau International des Poids et Mesures (BIPM), Sèvres,

Paris (1st CGPM (1889), CR 34-38).


Basic Unit of Time

Second is fundamental unit of time is the duration of exactly 9 192

631 770 periods of the radiation corresponding to the transition

between two hyperfine levels of the ground state of the caesium-

133 atom at a temperature of 0 K (13th CGPM (1967-1968)

Resolution 1, CR 103).


Basic Unit of Electrical Current

Ampere is fundamental unit of electrical current is the constant current which,

if maintained in two straight parallel conductors, of infinite length and

negligible cross-section, placed 1 meter apart in a vacuum, would produce a

force between these conductors equal to 2×10 −7 Newton per meter of length

(9th CGPM (1948) Resolution 7, CR 70).


Basic Unit of thermodynamic Temperature

Kelvin is fundamental unit of thermodynamic temperature (or absolute

temperature) is the fraction 1/273.16 (exactly) of the thermodynamic temperature

at the triple point of water (13th CGPM (1967) Resolution 4, CR 104).


Convert Measurement Units of LengthMeter to Inches

multiply by 39.37

Meter to Feet multiply by 3.281

Meter to Yards multiply by 1.094

Meter to Milesmultiply by 6.214 E-4.


Convert Measurement Units of MassConvert Measurement Units of Mass

Kilogram to PoundKilogram to Pound Multiply by 2.204621 Multiply by 2.204621


TOLERANCETOLERANCE

The total amount a dimension may vary. It is the difference between the maximum and minimum limits.

Way to express:1. Direct limits or as tolerance limits applied to a dimension2. Geometric tolerances3. A general tolerance note in title block4. Notes referring to specific condition


1. Direct limits and tolerance value

3.493.49

3.533.53

A) Direct limitsA) Direct limits

3.49 3.49 ± 0.003± 0.003

B) Tolerance valueB) Tolerance value


2. Geometric Tolerance System

Geometric dimensioning and tolerancing (GD&T) is a method of defining parts based on how they function, using standard ANSI symbols

ME 2304 Engineering Metrology & Measurement3. Tolerance Specification in Title

BlockGeneral tolerance note specifies the tolerance for all unspecified tolerance dimensions


4. Notes Referring to Specific Condition

General Tolerances could be in the form of a note similar to the one shown below:

ALL DECIMEL DIMENSIONS TO BE HELD TO ± .002”

MEANS THAT A DIMENSION SUCH AS .005 WOULD BE ASSIGNED A TOLERANCE OF ± 0.002, RESULTING IN UPPER LIMIT OF .502 AND A LOWER LIMIT OF .498


Important Terms – single part

Nominal Size – general size, usually expressed in common fraction (1/2” for the slot)

Basic Size – theoretical size used as starting point (0.500” for the slot)

Actual Size – measured size of the finished part (0.501” for the slot)

.502 Upper Limit (LMC).502 Upper Limit (LMC)

.498 Lower Limit (MMC).498 Lower Limit (MMC)


Important Terms – single part Limits – maximum and minimum sizes shown by tolerances

(.502 and .498 – larger value is the upper limit and the smaller value is the lower limit, for the slot)

Tolerances – total allowable variance in dimensions (upper limit – lower limit) – object dimension could be as big as the upper limit or as small as the limit or anywhere in between

AllowanceAllowance – the minimum clearance or maximum – the minimum clearance or maximum interference between partsinterference between parts

FitFit – degree of tightness between two parts – degree of tightness between two partsClearance fitClearance fit – tolerance of mating parts always leave a – tolerance of mating parts always leave a spacespaceInterference fitInterference fit – tolerance of mating parts always interfere – tolerance of mating parts always interfereTransition fitTransition fit – sometimes interfere, sometimes clear – sometimes interfere, sometimes clear


Shaft and Hole Fits


Tolerance Tolerance is permitted variation of size of a part to allow for

variation in manufacturing process Tolerance is indirectly a measure of quality, the smaller the

tolerance, the higher the quality; it is also related to the cost of production

Ideal interchangeable mating parts would be those without any kind of dimensional variation – exact size on blue print or specification


Questions Part A

1. Define –Metrology1. Define –Metrology2. State any two need for measurement.2. State any two need for measurement.3. Define error. How is it related to accuracy?3. Define error. How is it related to accuracy?4. Differentiate precision and accuracy.4. Differentiate precision and accuracy.5. Define the form “reliability”.5. Define the form “reliability”.6. Define the form “calibration”.6. Define the form “calibration”.7. What is meant by precision?7. What is meant by precision?8. What are the different types of errors?8. What are the different types of errors?9. Define the form “backlash”.9. Define the form “backlash”.10. Define the form “resolution”.10. Define the form “resolution”.11. Define the form “sensitivity”.11. Define the form “sensitivity”.12. Define the form “uncertainty”.12. Define the form “uncertainty”.13. Define the form “repeatability”.13. Define the form “repeatability”.14.Name the elements of measurement?14.Name the elements of measurement?15.Give any five methods of measurements?15.Give any five methods of measurements?16. Define the form “Precision”.16. Define the form “Precision”.17. Define the form “Accuracy17. Define the form “Accuracy18.Name the elements of measuring system?18.Name the elements of measuring system?


Questions Part B

1.Explain the needs for measurements in Metrology?

2.(a) What are the objectives of measurements.

(b) Explain briefly various types static errors involved in measurements.

3.(i) Describe with a good example precision and accuracy.

(ii) How does the reliability play the important role in quality?

4. Mention the various types of error and explain instrument loading errors and dynamic

errors.

5.(a) State and explain the five basic elements of measuring system.

(b) Describe the following types of errors

(i) Environmental error(i) Environmental error(ii) Parallax error(ii) Parallax error(iii) Cosine error.(iii) Cosine error.


Questions Part B

6. Differentiate between(i) Absolute error and relative error and (ii) Repeatability and6. Differentiate between(i) Absolute error and relative error and (ii) Repeatability and

reproducibility of measurement.reproducibility of measurement.

7. Explain the following terms.7. Explain the following terms.

(i) Calibration (ii) Reproducibility (iii) Sensitivity (iv) Magnification.(i) Calibration (ii) Reproducibility (iii) Sensitivity (iv) Magnification.

8.Define –Error. Explain about the errors in measurements and its causes in detail8.Define –Error. Explain about the errors in measurements and its causes in detail

Unit 1 - Introduction-METROLOGY

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Transcript of Unit 1 - Introduction-METROLOGY