chap7- engineering measurements

8/18/2019 Chap7- Engineering Measurements

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ChapterChapter 77

Engineering MeasurementsEngineering Measurements

PREP004 – Introduction to Applied Engineering

College of Engineering - University of Hail

Fall 2009

Examples of MeasurementsExamples of Measurements

♦♦CheckCheck youryour weightweight

♦♦Read your watchRead your watch

♦♦Take your temperatureTake your temperature

♦♦Read the speed indicator of your carRead the speed indicator of your car

What kinds of measurements did you makeWhat kinds of measurements did you make

today ?today ?


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Standards of MeasurementStandards of Measurement

,,

tool to compare some dimension of antool to compare some dimension of an

object to a standard.object to a standard.

Who needs good measurements?Who needs good measurements?

Engineers in IndustryEngineers in Industry

Doctors

Scientists

You and me (Every body)You and me (Every body)

Regulators (trade)


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Measurements for industry and tradeMeasurements for industry and trade

Design and develop newDesign and develop newproductsproducts

Manufacture of roducts thatManufacture of roducts thatmeet specificationsmeet specifications

Ensure compatibility andEnsure compatibility andinteroperability of productsinteroperability of products

Improve production processesImprove production processes

ReduceReduce scrapscrap

Improve Product QualityImprove Product Quality

nsure a r an equ a e ra e

80% of traded goods are based on

standards and regulations whereconformity assessment and hence

measurements are highly required.

Accurate, consistent measurement enables fairtrade.

WhyWhy measurements and metrologymeasurements and metrology

are importantare important??

It guarantees manufacturing quality andsupports innovation.

It makes an annual contribution of Billions ofDollars to wealth creation .

It underpins our safety, our health and ourualit of life.

It facilitates environmental management. It provides for effective regulations and Laws.

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Wrong measurements can beWrong measurements can be disastrousdisastrous

Measurement ErrorsMeasurement Errors

“Mission specifications called for“Mission specifications called forusingusing metric unitsmetric units, but the, but theLockheed group sent navigationLockheed group sent navigationinformation ininformation in BritishBritish unitsunits. The. Themixmix--up meant that Lockheedup meant that Lockheedengineers modelled navigationengineers modelled navigationwith pounds force (the Englishwith pounds force (the Englishunit for measuringunit for measuring thrusterthrusterimpulse) while JPL did itsimpulse) while JPL did itscalculations incalculations in newtonsnewtons (the(themetric measurement). One poundmetric measurement). One poundforce is equivalent toforce is equivalent to 44..4545newtonsnewtons.”.”

(Report on the loss of NASA’s Mars Orbiter spacecraft)

Systems of MeasurementsSystems of Measurements

British System of Measurements (BS)

Old system based on the inch (length)

The International System of

Units (SI) is the modern form of

and still in use in some industries

(petrochemicals) generally a system devised

around the convenience of the

number 10.

It is the world's most widely used

system of measurement, both in

industry, science and commerce.

PREPPREP004004 – – Introduction to Applied Engineering , College of Engineering,Introduction to Applied Engineering , College of Engineering, UoHUoH ٨


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International System (SI)International System (SI)

Seven Basic Units of MeasurementsSeven Basic Units of Measurements

PREPPREP004004 – – Introduction to Applied Engineering , College of Engineering,Introduction to Applied Engineering , College of Engineering, UoHUoH ٩

SI Derived UnitsSI Derived Units

PREPPREP004004 – – Introduction to Applied Engineering , College of Engineering,Introduction to Applied Engineering , College of Engineering, UoHUoH


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StandardStandard prefixesprefixes has been defined in orderhas been defined in order toto

measure very large and very small quanti tiesmeasure very large and very small quanti ties

PREPPREP004004 – – Introduction to Applied Engineering , College of Engineering,Introduction to Applied Engineering , College of Engineering, UoHUoH

Examples of use of PrefixesExamples of use of Prefixes

•• ExampleExample 11:: 1010--66 kg =kg = 11 mg (one milligram),mg (one milligram),

but notbut not 1010--66 kg =kg = 11 µkg (oneµkg (one microkilogrammicrokilogram))

•• ExampleExample 22:: Consider the example of the heightConsider the example of the height

of the Washin ton Monument. We ma write:of the Washin ton Monument. We ma write:

hhWW == 169 000169 000 mm =mm = 16 90016 900 cmcm

== 169169 m =m = 00..169169 kmkm


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Other Units of MeasurementsOther Units of Measurements

PREPPREP004004 – – Introduction to Applied Engineering , College of Engineering,Introduction to Applied Engineering , College of Engineering, UoHUoH ٣

What Engineers measureWhat Engineers measure

Engineering is a process that results in useful

products.

During his work, the engineer measures

products specifications (length, height, depth,

weight, etc..) and process characteristics

,of a turbine etc..)


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Why Engineers measure ?Why Engineers measure ?

To describe the current state of the process.

To state requirements quantitatively and

demonstrate compliance.

To track process and predict progress of

.

To analyze costs and benefits.

How do we measure ?How do we measure ?

•• UsingUsing measurementmeasurement

instrumentsinstruments (such as a caliper(such as a caliper

to measure the length of a workto measure the length of a work

piece or the voltmeter to measurepiece or the voltmeter to measure

the voltage of electrical currentthe voltage of electrical current

for example)for example)

•• Using aUsing a measurement system.measurement system.

PREPPREP004004 – – Introduction to Applied Engineering , College of Engineering,Introduction to Applied Engineering , College of Engineering, UoHUoH ٦


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Result of a MeasurementResult of a Measurement

XX : Measured Value: Measured Value

TT : True Value: True Value

EE : Error of Measurement: Error of Measurement

PREPPREP004004 – – Introduction to Applied Engineering , College of Engineering,Introduction to Applied Engineering , College of Engineering, UoHUoH ٧

Systematic Errors : Deal with them

by calibration of the measuring

instrument

Random Errors : Deal with

them by repeating themeasurements many times

and determine statistically

these errors.

Accuracy and Precision in Measurements Accuracy and Precision in Measurements Accuracy refers to how closely the measured value of a quantity corresponds to its

“true” value.

measurement accurac : closeness of a reement between a measured uantit

value and a true quantity value of the measurand.

Precision expresses the degree of reproducibility, or agreement between repeated

measurements.

Accuracy is tel ling the tru th and Precision is tell ing the same sto ry again and again.

PREPPREP004004 – – Introduction to Applied Engineering , College of Engineering,Introduction to Applied Engineering , College of Engineering, UoHUoH ٨

High Accuracy

High Precision

Low Accuracy

High Precision

Low Accuracy

Low Precision


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International and National Organizations forInternational and National Organizations for

Standards and MetrologyStandards and Metrology

e n erna ona rgan za on or

Standardization (ISO)

The International Office of Legal

Metrology (OIML)

PREPPREP004004 – – Introduction to Applied Engineering , College of Engineering,Introduction to Applied Engineering , College of Engineering, UoHUoH ٩

Mesures

Saudi Arabian Organization for

Standardization and Quality (SASOQ)

Home WorkHome Work 44--11

use touse to measure the following:measure the following:

A A.. TemperatureTemperature ____________________ ____________________

BB.. VolumeVolume ____________________ ____________________

CC. Length. Length ___________________ ___________________

D.D. TimeTime ____________________ ____________________

E.E. WeightWeight ____________________ ____________________

F.F. Pressure ____________________ Pressure ____________________


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Home WorkHome Work 44--22

following conversions :following conversions :

A A.. T=T= 6565 C = ……. F = ………. K = ……C = ……. F = ………. K = ……

BB.. V =V = 1010 Gallons = …… l = ……. mGallons = …… l = ……. m33

CC. L =. L = 15401540 miles = …… km = …….. m = …. inchmiles = …… km = …….. m = …. inch

D.D. T =T = 1515 h = ……… min = ……… s = ….. dayh = ……… min = ……… s = ….. day

E.E. use any measurement results and make theuse any measurement results and make the

necessary conversions.necessary conversions.

Research QuestionResearch Question 44--33

What is aWhat is a vernier vernier calipercaliper and how does itand how does it

work?work?

Give some engineering situations where thisGive some engineering situations where this

instrument is used .instrument is used .

State some illustrations and examples.State some illustrations and examples.


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Additional Readings Additional Readings

http://en.wikipedia.org/wiki/International_System_of_Unitshttp://en.wikipedia.org/wiki/International_System_of_Units

http://hctmetrology.tripod.comhttp://hctmetrology.tripod.com (Arabic web on dimensional metrology)(Arabic web on dimensional metrology)

PREPPREP004004 – – Introduction to Applied Engineering , College of Engineering,Introduction to Applied Engineering , College of Engineering, UoHUoH ٢٣

Thank ouThank ou

Any Questions ? Any Questions ?

PREPPREP004004 – – Introduction to Applied Engineering , College of Engineering,Introduction to Applied Engineering , College of Engineering, UoHUoH ٢٤

chap7- engineering measurements

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