Chapter 7Chapter 7

Engineering MeasurementsEngineering Measurements

PREP004 – Introduction to Applied Engineering

College of Engineering - University of Hail

Fall 2009

Examples of MeasurementsExamples of Measurements

You are making a measurement when youYou are making a measurement when you

Check your weight Check your weight

Read your watchRead your watch

Take your temperatureTake your temperature

Read the speed indicator of your car Read the speed indicator of your car

What kinds of measurements did you make What kinds of measurements did you make today ?today ?

Standards of MeasurementStandards of Measurement

When we measure, we use a When we measure, we use a measuring tool to compare some measuring tool to compare some dimension of an object to a standard.dimension of an object to a standard.

Who needs good measurementsWho needs good measurements??

Engineers in IndustryEngineers in Industry

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

Regulators (trade)

Doctors

Scientists

Measurements for industry and tradeMeasurements for industry and trade

Design and develop new productsDesign and develop new products Manufacture of products that meet Manufacture of products that meet

specificationsspecifications Ensure compatibility and Ensure compatibility and

interoperability of productsinteroperability of products Improve production processesImprove production processes Reduce scrapReduce scrap Improve Product QualityImprove Product Quality

Ensure fair and equitable trade

80% of traded goods are based on standards and regulations where conformity assessment and hence measurements are highly required.

Accurate, consistent measurement enables fair trade.

It guarantees manufacturing quality and supports innovation.

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

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

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

Why measurements and Why measurements and metrology are important?metrology are important?

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Wrong measurements can be disastrousWrong measurements can be disastrousMeasurement ErrorsMeasurement Errors

““Mission specifications called Mission specifications called for using for using metric unitsmetric units, but the , but the Lockheed group sent navigation Lockheed group sent navigation information in information in British unitsBritish units. . The mix-up meant that The mix-up meant that Lockheed engineers modelled Lockheed engineers modelled navigation with pounds force navigation with pounds force (the English unit for measuring (the English unit for measuring thruster impulse) while JPL did thruster impulse) while JPL did its calculations in newtons (the its calculations in newtons (the metric measurement). One metric measurement). One pound force is equivalent to pound force is equivalent to 4.45 newtons.”4.45 newtons.”

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

Systems of Measurements Systems of Measurements

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British System of Measurements (BS)

Old system based on the inch (length) and still in use in some industries (petrochemicals)

The International System of Units (SI) is the modern form of the metric system and is 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.

International System (SI)International System (SI)

Seven Basic Units of MeasurementsSeven Basic Units of Measurements

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SI Derived Units SI Derived Units

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Standard Standard prefixesprefixes has been defined in order has been defined in order to to measure very large and very small quantitiesmeasure very large and very small quantities

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Examples of use of PrefixesExamples of use of Prefixes

• Example Example 11: 10: 10-6-6 kg = 1 mg (one milligram), kg = 1 mg (one milligram),

but notbut not 10 10-6-6 kg = 1 µkg (one microkilogram) kg = 1 µkg (one microkilogram)

• Example Example 2:2: Consider the example of the height Consider the example of the height of the Washington Monument. We may write:of the Washington Monument. We may write:

hhWW = 169 000 mm = 16 900 cm = 169 000 mm = 16 900 cm

= 169 m = 0.169 km= 169 m = 0.169 km

Other Units of MeasurementsOther Units of Measurements

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What Engineers measureWhat Engineers measure

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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 (Temperature and pressure of fluid flows, speed of a turbine etc..)

Why Engineers measure ?Why Engineers measure ?

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To describe the current state of the process.

To state requirements quantitatively and demonstrate compliance.

To track process and predict progress of engineering project.

To analyze costs and benefits.

How do we measureHow do we measure? ?

• Using Using measurement measurement instruments instruments (such as a caliper (such as a caliper to measure the length of a work to measure the length of a work piece or the voltmeter to measure piece or the voltmeter to measure the voltage of electrical current the voltage of electrical current for example)for example)

• Using a Using a measurement system.measurement system.

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Result of a Measurement Result of a Measurement

XX : Measured Value : Measured Value

TT : True Value : True Value

EE : Error of Measurement : Error of Measurement

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Systematic Errors : Deal with them by calibration of the measuring instrument

Random Errors : Deal with them by repeating the measurements many times and determine statistically these errors.

Accuracy and Precision in MeasurementsAccuracy and Precision in Measurements

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Accuracy refers to how closely the measured value of a quantity corresponds to its “true” value.

measurement accuracy : closeness of agreement between a measured quantity value and a true quantity value of the measurand.

Precision expresses the degree of reproducibility, or agreement between repeated measurements.

Accuracy is telling the truth and Precision is telling the same story again and again.

High Accuracy

High Precision

Low Accuracy

High Precision

Low Accuracy

Low Precision

International and National Organizations for International and National Organizations for Standards and MetrologyStandards and Metrology

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The International Organization for Standardization (ISO)

The International Office of Legal Metrology (OIML)

Bureau International des Poids et des Mesures

Saudi Arabian Organization for Standardization and Quality (SASOQ)

Home Work 4-1Home Work 4-1

SState the tool (s) and the Units you would tate the tool (s) and the Units you would use to measure the following:use to measure the following:

AA. Temperature. Temperature ________________________________________

BB. Volume . Volume ________________________________________

CC. Length. Length ________________________________________

D.D. Time Time ________________________________________

E.E. Weight Weight ________________________________________

F.F. Pressure ____________________ Pressure ____________________

Home Work 4-2Home Work 4-2

Use any online converter to make the Use any online converter to make the following conversions :following conversions :AA. T= 65 C = ……. F = ………. K = …… . T= 65 C = ……. F = ………. K = ……

BB. V = 10 Gallons = …… l = ……. m3. V = 10 Gallons = …… l = ……. m3

CC. L = 1540 miles = …… km = …….. m = …. inch. L = 1540 miles = …… km = …….. m = …. inch

D.D. T = 15 h = ……… min = ……… s = ….. day T = 15 h = ……… min = ……… s = ….. day

E.E. use any measurement results and make the use any measurement results and make the necessary conversions. necessary conversions.

Research Question 4-3Research Question 4-3

What is a What is a vernier caliper vernier caliper and how does it and how does it work? work?

Give some engineering situations where this Give some engineering situations where this instrument is used .instrument is used .

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

Additional ReadingsAdditional Readings

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

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

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Thank youThank you

Any Questions ?Any Questions ?