Industrial Inspection Measurement

• Course Title: Metrology and Machine Drawing
• Course Code: 21ME35
• Unit 1

Concepts of Measurements

• Topics covered: Methods, errors, accuracy, precision, repeatability, standards, wavelength standard, modern meter, hierarchical classification, line and end measurements, end bar calibration, measurement systems, and generalized measurement system.

Transducers

• Topics covered: Characteristics transfer efficiency, primary and secondary, and mechanical transducers.

Exploration of Measurement History

• In ancient Egypt, carpenters used rulers attached to their bodies, preventing misplacement.
• A span is measured from the tip of the thumb to the tip of the little finger on an outstretched hand
• It was considered half a cubit.
• A cubit is measured from the tip of the middle finger to the front of the elbow.

Ancient vs Modern Measurement Instruments

• Ancient instruments include foot steps, ropes, hand spans, and arm lengths.
• Modern instruments include rulers, measuring tapes, screw gauges, and vernier calipers.

Measuring device examples

• Stainless steel rulers, vernier calipers and micrometers are examples of measuring instruments

Evolution of Standards

• A historical overview reveals interesting facts.
• The Egyptian cubit was the earliest length standard, defined as the Pharaoh's forearm plus palm width
• Made of black granite, used in pyramid construction.
• The actual foot length of the Greek monarch was the definition of a foot.
• King Henry I decreed a yard to be the length from nose tip to fingertip of an outstretched arm.
• 1795: France accepted the metric system, coexisting with medieval units.
• 1840: the metric system became the only system of weights and measures
• 1798: Eli Whitney introduced interchangeable parts manufacturing for assembling guns.
• Resulted in standardization for better interchangeability.
• 1855: England developed the imperial standard yard, which was quite accurate.
• 1872: France developed the first international prototype meter.
• 1875: the International Metric Convention in France accepted the metric system internationally.
• The International Bureau of Weights and Measures (BIPM) in Paris was set up, signed by 17 countries.
• 1866: the USA allowed the use of metric weights and measures in contracts and legal proceedings.
• 1893: the USA adopted international metric standards as basic measurement standards.
• Around 35 countries officially adopted the metric system in 1900, including continental Europe and most of South America.
• Various international organization standardizations occurred, including:
• The International Electrotechnical Commission (IEC) in 1906
• The International Organization for Standardization (ISO) in 1947.
• October 1960: The original metric standards were redefined at the 11th General Conference on Weights and Measures in Paris.
• The SI units were devised
• SI stands for système international d'unités (international system of units).
• 1999: A mutual recognition arrangement (MRA) was signed by the Committee of Weights and Measures.
• Aim: to provide reliable, comparable quantitative information for metrology services.

Introduction to Measurements

• Defined as the process of obtaining a quantitative comparison between a predefined standard and an unknown magnitude.
• Requirements:
• Standards must be accurately known.
• Procedure & apparatus -commonly accepted & provable.

Significance of Measurement System

• Provides a fundamental basis for R&D.
• Acts as a fundamental element of any process control.
• Required to ensure proper performance.
• Forms the basis of commerce.

General Measurement Concepts

• Industrial inspections primarily objectives to find the quality of manufactured components
• Quality requirements that are considered:
• Permissible tolerance limits
• Form
• Surface Finish
• Size
• Flatness
• Quantitative information on physical objects or processes requires a comparison with a reference.

Fundamentals of Measurement Systems

• In measurement systems, the basic elements are a measurand, comparator and reference
• Measurand: A physical quantity like length, weight, or angle to be measured.
• Comparator: For comparing the physical measurand with a reference standard during evaluation.
• Reference: A physical property or quantity on which quantitative comparison are made, internationally accepted.
• Direct measurement requires using the the 3 elements with a calibrated fixed reference
• Determining length needs comparing the component (measurand) with e.g. a steel scale (reference).

Methods of Measurement

• Measurements determines the magnitude of a quantity and its unit
• For example, a rod's length is measured with a unit.
• Measurements of this kind depends on both accuracy and the amount of error allowed
• Primary objective: minimize the uncertainty associated with any measurement
• Common measurement methods:
• Direct
• Indirect
• Fundamental or absolute
• Comparative
• Transposition
• Coincidence
• Deflection
• Complementary
• Null
• Substitution
• Contact
• Contactless
• Composite
• Direct method: requires direct quantity comparison to standard with tools like scales or micrometers.
• It is widely used in production; however some difference is present in values because of human limitations
• Indirect method: Requires obtaining the quantity value using mathematical relationship.
• For example: angle measurement with sine bar.
• Fundamental/absolute method: measurements of base quantities defines the direct measure without indirect measures.
• Comparative method: comparing quantity directly with master gauge, e.g using comparators, dial indicators, etc.
• Transposition method: Initial comparison of the quantity with a known measure balanced, and then measured again. If the quantities are equal it is equal to V = √XY.
• This can be observed in a mass balance.
• Coincidence: measuring the reference and minute differences between the two. Measurements on Vernier caliper and micrometer are examples.
• Deflection: indicates the value of the quantity directing the measurement. Pressure measurement is an example.
• Complementary: value of the quantity combines with the sum of two other factors
• Null method: the difference between 2 values is brought to zero
• Substitution: replaces quantity measured with an equivalent quantity, e.g. Borda's method of mass
• Contact: surfaces are touched by an instrument tip, e.g. with micrometer, vernier caliper, and dial indicator
• Contactless: surface is only measured, e.g. tool maker's microscope, and profile projector.
• Composite: checking the contour of a component with combined tolerence, e.g. going GO gauges

Generalized System of Measurement

• Length and mass can be measured using measuring instruments.
• However, temperature, force, and pressure have no direct measurement methods
• Transducer's change energy not measurable into the easily measurable
• Determining input and output value to assess each input
• Has three stages:
• Performs stages of measure
• Displays the value of the output

Generalized Measurement System: Stages

• Stage I: Detector/transducing/sensor stage
• Stage II: Intermediate/modifying/signal conditioning stage
• Stage III: Terminating/read-out stage
• The block diagram of the generalized measuring system shows the flow of calibration input, auxiliary power, measurand, and resulting signals through the sensor-transducer, signal conditioner, and various output components like indicators, recorders, computers, processors, and/or controllers.
• A general system's block diagram also consists of input signals, detectors, auxiliary power, transducers, modifying stage, resulting output, and controllers

Generalized Measurement System: Stage Breakdown

• Stage I: Detector-Transducer
• Function: to sense input and convert it into an analogous signal for simple measurement.
• Input signal: physical quantity of the device used, known as a transducer or sensor.
• The transuder coverts the signal for mechanical, electrical, optical or thermal elements.
• The resulting generated is further refined in the second stage.
• Tranducers should only detect input used/measure and exclude others
• Stage II: Intermediate Modifying
• The transduced signial is modeified with coditioning and processing efore display
• Functions like noise, signal conditioning can help increase the noise ratio
• Integration and derivitizaion of the signals happen before output is shown
• Stage III: Output/Terminating
• Presents the analogous input value either for records
• Indications can be scales, pointers etc
• Cannot directly perform physical quantities.
• Signal will often move a pointer

Example of Generalized Measurement System

• Tyre pressure measurement systems uses:
• A piston and cylinder
• A compression spring
• When the cylinder is pressurized it moves the spring
• That will move a calibrated stem along the calibrated stem
• Piston and stem together forms a transducers of pressure to force
• The resulting signal moves out to the scale
• Measuring acceleration is complex
• First stage device, measures acceleration and provides analogous voltage
• In addition to the voltage amp, the second stage allows the attenuation of frequency
• It combines the signals to to provde velocity-time measures instead
• Lastly the printer records from the data aquisition

SI Fundamental Units include:

• Length: meter (m)
• Mass: kilogram (kg)
• Time: second (S)
• Electric current: ampere (A)
• Temperature: Kelvin (K)
• Amount of substance: mole (mol)
• Luminous intensity: candela (cd)

SI Derived Units Table

| Area | square meter | m² | | Volume | Cubic Meter | m³ | | Speed | m/s | | Acceleration | m/s2 | | Weight/Force | newton | N | | Pressure | Pascal | Pa |
| Working Energy | Joule | J |

SI Supplementary Units Table

Plane Angle | Radian | rad Solid angle | Stratdian | sr

Standards of Measurement

• During the medieval period measurement processes existed with no standard methods of measure set
• Comparisons with known quantities is important to measuring
• Quantities has a unit and must be accepted internationally
• A standard is defined as a value of any known physical quantity found nationally/internationally that can reproduce
• Fundamental units: length, mass time and temp
• All manufacturers must adhere to the same standards to ensure measurements have the same quality, precision, repeatability

Measurements Standards Laboratory Organizations

• International:
• Organization of legal metrology, Paris
• Bureau of Weigths and measure, Sevres in France
• National Physical Laboratory, India

Material Standard

• Standard system for linear measurement: yards and metric systems
• Most countries recognize that the metric system and meters are the most fundamental linear measurement Problem Material Standards have: standards change size wuth temperature etc
• in keep standards unchanged care and attention had to be exercised to maintain the conditions. Primary - standard - natural/invariable found - wavelength of monochromatic light - environment
• Unit is defined as: The distance - bar of metail = maintained under certain conditions - temperature and support

Standards of Measurement List

• First- Imperial standard Yard-England.
• Second- International Prototype Meter- France.
• Wavelength standard.

Imperial Standard Yard Composition

• Imperial Standard Yard: made of a bronze bar; cross-section of 1 sq. inch and inches in length.
• Composed of 82% Cu, 13% tin, and 5% Zn.
• Holds 1/2 inch length in diameter
• extends to the bar's center plane
• A polished plug 0.1 inches in diameter and 3 transverse lines +2 lines lies in the neutral plane.
• The plug is used to maintain at a temperature of 62°F.
• Legalized in 1853 but, the standard remained legal until replace in 1960
• Maintaing the plug at the neutral axis prevents axis bending
• Plug protected, error occur at ends, slop on side. face parallel with each other.

Further Imperial Standard Yard Info

• Airy Point's prevent the bar bending
• To minimize error due to bending, Airy Points should be used as supporting points.
• Where d, shows the distance d = *sqrt(n^2 - 1) * L
• when supports equal 2. it produces .577L
• The supports be an eaual distance away with .577L apart
• In general the airy points are marked for length bars greater/ less than 150mm

More Info On Airy Points

• To prevent bending of support its is optional to have horizontal rod supported "Airy Points"
• Neutral axis: a line through which maintainng lines helps bending.
• "Another to get away" getting damage

Differences Between Airy Points and Bessel Points

• Airy points (end faces are parallel)
• Used for long bars above 150mm, measuring pull-ups
• Distance between is .577L with no ends
• Bessel Points (minimum deflection)
• 0.554L, for sagging at point support

International Protype Info

• (1875 - International Bureau of Weights and Measures)
• meter is defined as - positions of line - by highly metal
• (platinum/iriduim) in the alloy maintan under nomal atmostphere
• This section are known as "Web"

Web Section - Advantages

• 1 The section is uniform
• graduations on natural axis allow its whole be graduated
• 2 provide and economic even through-out
• In oxidizable and produce good lines

International Prototype Meter

• It is supported with with at least 1 meter diameter rollong which each other at 751mm
• Max rigidity and cost effects material

Material standards - Disadvantages

• Affect, temperartue and pressure - age - variations
• Preservation - Difficult appropritate the security - the destuct
• Replica : NO aVailable for usage
• Can't be produced easily
• Sizes = difficult
• conversion factor

Wavelength Information

• Wavelengths will have natural and uniform lengths
• Eliminate the depency for the working standard's
• Defintion: length to wavelength with term lengths
• Light waves - working - practical
• There were uses on wave length because of the impossible

Wave Length Standard

• Preservation is unnecessary for the wavelength strandard
• Production is can reproduce
• 1960 - General confernce Weights - Paris
• Krypton 85 = element lamp 68 K.
• (1,650,763.73 red-orange radiation = in vacuum)
• Yard = 1,509,658-35 = orange iscope (Yard = 0.9144 meter)
• Accuracy = 1 part = lab.

wave length/Optical length

• light radiation of orange

wave length standards: advantages

• length dose not change/variation in surroundings conditions
• dose not be stored. preserved/ reproduced easy
• the instrument for very accuracy comparatives
• Not destruction of - wear and tear

Metre as of today

• Length a travel light
• General 17 the conference of Weights and Measures, 20
• October 1983 defined = the length path a travel = 1/2 second
• (Krypton or use use of an iodine - laser

Sub division

• primary
• Secondary
• Tertiary
• Working standars

Hierarchy of standards

Essential is - - to a material paris

• No application engineering
• 10 - 20 compare years
• Secondary: Copies designs material = lengthy
• custody every - laboratety Comparison - tertiary loss •Primary

Sub of standars-

• Tertiary. employ first refernces - and workshop True - copies working standards on metroloyy laboraties.

Hierarchial Classification of Standards

• Precision and maintaible source for contact The BIPM
• identical Dimensions compatiable
• Frequent degradation frequent to national standafds
• standards - Interlaborary derive - working

Quality Control

• Scale engraved, Quick Easy
• Markings - wear built
• Parallax error
• Magnifying lens/

END standars

• length measurements of a "parallel end face"
• Very acuurate
• Time consuming
• Subject and no para
• Form a to the end

Transducer:

Quality Principle measurment/Accuracy

TRANSFER FROM LINE STANDARD TO END STANDARD

• First step to find Standard, The workshop stander
• (High inconveniert - cailbarte provided known
• Small error. - deterimie othe be with.

TRANSFER FROM LINE STANDARD TO END STANDARD CONTINUED

• Define: highly
• Special
• Highest

TRANSFER FROM LINE STANDARD TO END STANDARD (NPL)

End blocks on the gauge the blocks are engraved surface at . It wringing

Known to do so the

• 35 - comparator with wire

TRANSFER FROM LINE STANDARD TO END STANDARD (LINE - BROOKE 'S) CONTINUED

If = differences Wringing 1 + b + c = 36+ /+ Then a by one by

Level : By comparator

• Brooke' the it - may noted.

Actual / be

TRANS - BROKE LEVEL COMPARATOR.

"1/2 inch block" and other values in figures

Calibration of

Actual - end ( Together &

They, with to set the in them.

Calibration

The : the is to.

• calibarte =the bar a

Fundamentals and equation of of "length"

• the . A A L1

ACCURACY

• reading • Degree its • Amount • near, value -

True Value

• values the -deviation -to zero Value = be each

-Accurate Instruments:

• eliminate

• Eliminate

•calibrate: constant

Accurate measurements, affecting of calibration +:

•-Coefficient expansion.

• Internal

• Properties • Stability: •-Cleanliness:

•-Deffects workpiece: Adequate,

• Consistency
• Precision :. person:

•-and

•Surrounding:" Illuminate:

•-PRECISION. degree of or the -to.

•The -to known random, = though •To Scale

• instrument be measurements,•More

ACCURACY PRECISION and REPEATABLE:

• Five factors may contribute - that's are: number, calibration,

• Precision == both

•-Repeatable = to constnat "•Reproducibility", variability vary

###" The "" REPEATABLE &"" pertaining ( time and observer to

The "REPRODUCIBILITY,"

To change the measurement , observer and time measurement

• Calibration - instrument to to

Standard with that a Standard

SENSITIVITY

•The : to small

rate an the and

• The "to a : the. space :

• factor/ units, Operation with change units

• Output ::= gain Optical = amplification

SENSITIVITY (10μV/°C

"" -indicates spring

• External" then (0.2, 0°C
• Internal" instruments.

Sensitivity:

• To linear, =instrument The, linearr.1 •-LINEARITY the to

• is:

• time or or if the classified analog. The into time, The analog transducer
• Electrical digital. The functions

• that to numbers Encoder,. and Opaque a •: the -

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Assess manufactured component quality through tolerance, form, surface finish, size, and material properties. Quantitative data from a physical object or process requires standard comparison. Measurement systems compare physical quantities internationally, considering measurands, comparators, and calibrated references.