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SIE1004

MEASUREMENT & SENSOR TECHNOLOGY

WEEK 1

FUNDAMENTAL OF MEASUREMENT

25/8/2014 SIE1004 Measurement & SensorTechnology

1


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WEEK 1

Fundamental of Measurement

Measurement Mode

Type of measurementStandards and SI System


2


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Why do we need measurement?

Why do we need to know sensor technology?

List 5 things related to measurement and sensors

that you have experienced today.


3


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CONTENT OF THE CHAPTER


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What is measurement;

Operational modes of measurement;

Measurement standards;

SI Units and applications.


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SIMPLE MEASUREMENT MODEL


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Simple Measurement Model (Ref. 1)

Common Physical Variables Length, Distance, Velocity, Level, Force, Stress, Strain,Pressure, Temperature, Flow, etc.

Typical Signal Variables Voltage, current, displacement, etc.


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MASS MEASUREMENT


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What are the variables in this measurement?1. Measurand:

2. Measurement Variable X:

3. Signal Variable S:

4. Measurement M:


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LETS PLAY


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List an example of measurand that you areinterest;

Invite your neighbour to suggest a possible

measurement variable, signal variable andthe way of measuring.

Suggest a possible solution to the measurand

that your neighbour is interested.


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SIMPLE MEASUREMENT MODEL


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Simple Measurement Model (Ref. 1)

Common Physical Variables Length, Distance, Velocity, Level, Force, Stress, Strain,Pressure, Temperature, Flow, etc.

Typical Signal Variables Voltage, current, displacement, etc.


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MEASUREMENT IN DIGITAL WORLD


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Stages in measuring system [ref. 3]

A sample control system with measurement [ref. 4]


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OPERATIONAL MODES


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Null Mode for measurementThe instrument exerts an influence on the measured system so as to oppose the

effect of the measurand. The influence and the measurand are balanced until they

are equal but opposite in value, yielding a null measurement.

An example of NULL measurement (Ref. 1)


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FEEDBACK PRINCIPLE OF NULL METHOD


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The influence and the measurand are balanced until they areequal but opposite in value, yielding a null measurement.

Typically, this is accomplished by some type of feedback

operation that allows the comparison of the measurand

against a known standard value.

Comparison and feedback for NULL

Measurement Mode (Ref. 1)


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DEFLECTION MODE


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Deflection Mode for Measurement

An example of Deflection measurement (Ref. 1)


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STRAIGHTFORWRD LOGIC


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A deflection instrument is influenced by the measurand so asto bring about a proportional response ;

This response is an output reading that is a deflection or a

deviation from the initial condition of the instrument;

In a typical form, the measurand acts directly on a primeelement or primary circuit so as to convert its information

into a detectable form.

Logic flow chart for a deflection mode measurement (Ref. 1)


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COMPARISON OF TWO MODE


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Which mode may offer better accuracy?

Which mode may be more suitable for

dynamic measurement?


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COMPARISON: Pros and Cons


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NULL Pros:

Cons:

Deflection Pros:

Cons:

More reading on NULL & Deflection Instrument can be found at

http://dsp-book.narod.ru/MISH/CH02.PDF
http://dsp-book.narod.ru/MISH/CH02.PDFhttp://dsp-book.narod.ru/MISH/CH02.PDFhttp://dsp-book.narod.ru/MISH/CH02.PDF


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WE NEED MEASUREMENT STANDARD


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How much is a Tael?


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MEASUREMENT STANDARDS


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Standard of Practice (Ref. 1)


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DISCUSSION


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Why do we need standards?

Who is in charge of the measurement

standard in Singapore?


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How much is 1 fl oz in ml?

How much is 1 ml in fl oz?

If a baby is to take 5 fl oz milk, how

much ml to be given?


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CAN YOU FIND THE DIFFERENCE?


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HERE IS THE DIFFERENCE


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THREE SYSTEM OF UNITS


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SI Units: International System of Units

Centimeter-gram-second (CGS)-Gaussian Units

Imperial units: British system.

http://en.wikipedia.org/wiki/File:SI_base_unit.svg

http://en.wikipedia.org/wiki/Centimetre%E2%80%

93gram%E2%80%93second_system_of_unitshttp://upload.wikimedia.org/wikipedia/comm

ons/c/c8/English_length_units_graph.png
http://en.wikipedia.org/wiki/File:SI_base_unit.svghttp://en.wikipedia.org/wiki/File:SI_base_unit.svghttp://en.wikipedia.org/wiki/Centimetre%E2%80%93gram%E2%80%93second_system_of_unitshttp://en.wikipedia.org/wiki/Centimetre%E2%80%93gram%E2%80%93second_system_of_unitshttp://en.wikipedia.org/wiki/Centimetre%E2%80%93gram%E2%80%93second_system_of_unitshttp://upload.wikimedia.org/wikipedia/commons/c/c8/English_length_units_graph.pnghttp://upload.wikimedia.org/wikipedia/commons/c/c8/English_length_units_graph.pnghttp://upload.wikimedia.org/wikipedia/commons/c/c8/English_length_units_graph.pnghttp://upload.wikimedia.org/wikipedia/commons/c/c8/English_length_units_graph.pnghttp://en.wikipedia.org/wiki/Centimetre%E2%80%93gram%E2%80%93second_system_of_unitshttp://en.wikipedia.org/wiki/File:SI_base_unit.svg


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SI UNITS


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Fundamental/Base Quantities/Units Fundamental units are not definable in term of

other units;

There are 7 fundamental units in SI

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

e:SI_base_unit.svgTable of Fundamental/Base SI Quantities/Units (ref 2.)
http://en.wikipedia.org/wiki/File:SI_base_unit.svghttp://en.wikipedia.org/wiki/File:SI_base_unit.svghttp://en.wikipedia.org/wiki/File:SI_base_unit.svghttp://en.wikipedia.org/wiki/File:SI_base_unit.svg


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SI UNITS AND BRITISH UNITS


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Comparison between SI Units and BritishUnits [ref 3].

1 = 2.2046lb

http://www.metric-conversions.org/weight/pounds-to-kilograms.htm

1 = 3.2808ft

http://www.metric-conversions.org/length/meters-to-feet.htm

( ) = 1.8 ()

http://www.rapidtables.com/convert/temperature/kelvin-to-rankine.htm
http://www.metric-conversions.org/weight/pounds-to-kilograms.htmhttp://www.metric-conversions.org/weight/pounds-to-kilograms.htmhttp://www.metric-conversions.org/length/meters-to-feet.htmhttp://www.rapidtables.com/convert/temperature/kelvin-to-rankine.htmhttp://www.rapidtables.com/convert/temperature/kelvin-to-rankine.htmhttp://www.rapidtables.com/convert/temperature/kelvin-to-rankine.htmhttp://www.metric-conversions.org/length/meters-to-feet.htmhttp://www.metric-conversions.org/weight/pounds-to-kilograms.htm


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UNIT OF LENGTH (meter)


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The 1889 definition of the meter, based on the internationalprototype of platinumiridium, was replaced by the 11th

CGPM (1960) using a definition based on the wavelength of

krypton 86 radiation.

The current definition is: the meter is the length of the pathtravelled by light in vacuum during a time interval of 1/299

792 458 of a second.

It follows that the speed of light in vacuum is exactly 299 792

458 meters per second, c0 = 299 792 458 m/s.


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UNIT OF MASS (kilogram)


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The kilogram is the unit of mass; it is equal to the mass ofthe international prototype of the kilogram..

The international prototype of the kilogram, an artifact made

of platinum-iridium, is kept at the BIPM under the conditions

specified by the 1st CGPM in 1889 (CR, 34-38)

http://en.wikipedia.org/wiki/File:CGKilogram.jpg


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UNIT OF TIME (second)


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The second is the duration of 9 192 631 770 periods of theradiation corresponding to the transition between the two

hyperfine levels of the ground state of the cesium 133

atom..

It follows that the hyperfine splitting in the ground state ofthe cesium 133 atom is exactly 9 192 631 770 hertz,

(133Cs)hfs = 9 192 631 770 Hz.

This definition refers to a cesium atom at rest at a

temperature of 0 K.


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UNIT OF ELECTRIC CURRENT (ampere)


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The ampere is that constant current which, if maintained intwo straight parallel conductors of infinite length, of

negligible circular crosssection, and placed 1 meter apart in

vacuum, would produce between these conductors a force

equal to 2 10-7newton per meter of length.

It follows that the magnetic constant, also known as the

permeability of vacuum, is exactly 4 10-7 henries per

meter, = 4 10 10-7 H/m.


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UNIT OF TEMPERATURE (kelvin)


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The kelvin, unit of thermodynamic temperature, is thefraction 1/273.16 of the thermodynamic temperature of the

triple point of water.

It follows that the thermodynamic temperature of the triple

point of water is exactly 273.16 kelvins, TTPW = 273.16 K.


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UNIT OF SUBSTANCE (mole)


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The mole is the amount of substance of a system whichcontains as many elementary entities as there are atoms in

0.012 kilogram of carbon 12; its symbol is mol.

When the mole is used, the elementary entities must be

specified and may be atoms, molecules, ions, electrons,other particles, or specified groups of such particles.

It follows that the molar mass of carbon 12 is exactly 12

grams per mole, M(12C) = 12 g/mol.


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UNIT OF LUMINOUS INTENSITY(candela)


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The candela is the luminous intensity, in a given direction,of a source that emits monochromatic radiation of

frequency 540 1012 hertz and that has a radiant intensity

in that direction of 1/683 watt per steradian.

It follows that the spectral luminous efficacy formonochromatic radiation of frequency of 540 1012 hertz is

exactly 683 lumens per watt, K(555) = 683 lm/W= 683 cd

sr/W (the wavelength of radiation of this frequency is about

555 nm).


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INTERDEPENDENCE OF BASE UNITS


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The seven SI base units and the interdependency of their

definitions.

http://en.wikipedia.org/wiki/File:SI_base_unit.svg


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SI DERIVED UNITS


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Derived units are products of powers of base units. Coherent derived units are products of powers of

base units that include no numerical factor other

than 1.


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COHERENT DERIVED UNITS


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Examples of coherent derived units in SI expressed in term of base units (ref 2.)


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UNIT CONVERSION


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Simple & Basic Math Rule: Any number orexpression can be multiplied by 1 without

changing its value.

1 inch = 2.54 cm 1 = .5

= .5

How many cm are in 5 inches?

More exercises can be found at:

http://www.chem.tamu.edu/class/fyp/mathrev/mr-da.html
http://www.chem.tamu.edu/class/fyp/mathrev/mr-da.htmlhttp://www.chem.tamu.edu/class/fyp/mathrev/mr-da.htmlhttp://www.chem.tamu.edu/class/fyp/mathrev/mr-da.html


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DIMENSIONAL ANALYSIS


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Dimension Analysis: dimensions can be usedas a help in validating and estimating

relationships between the derived units and

fundamental units. The dimension of both L.H.S. and R.H.S.

should be the same in any formula and

equations. Only the same dimension can do addition and

subtraction.


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DIMENSION OF DERIVED QUANTITIES


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Derived quantities

Dimension quantities (incomplete set) from

http://web.mit.edu/2.25/www/pdf/DA_unified.pdf
http://web.mit.edu/2.25/www/pdf/DA_unified.pdfhttp://web.mit.edu/2.25/www/pdf/DA_unified.pdfhttp://web.mit.edu/2.25/www/pdf/DA_unified.pdf


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EXAMPLE of DIMENSION ANALYSIS


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If we look into the water pressure: P =gh

Dimension Analysis:

L.H.S. [P] = [mass] [acceleration]/[area]

or [P] = (M)(Lt-2)/ L2 = M L-1 t-2

R.H.S. [] = M L-3; g = L t-2; [h] = L

or [gh] = (M L-3)(L t-2)(L) = M L-1 t-2

L.H.S.=R.H.S. However, dimensional analysis cannot guarantee the equation to be correct as it

does not cover the quantity/factor part.


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DIMENSION ANALYSIS EXAMPLE


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For example, you derived an equation:P=

Dimension Analysis:

Dimension of L.H.S.= [ML2t-3];

Dimension of R.H.S.=[M][Lt-1][Lt-1]=[ML2t-2]

There is a mis-match and you may consider

E=


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LEARNING OUTCOME


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To describe and comprehend thefundamental and process of measurement

and interpret the standards.

Measurement process (X, S, M)

Measurement modes (NULL, Deflection)

Measurement standards

Unit conversion Dimensional analysis


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REFERENCES

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1. Measurement, Instrumentation and Sensors Handbook, Edited by John G. Webster,CRC Press & IEEE Press, 1999.

2. The International System of Units (SI), by National Institute of Standards and

Technology. Available online: http://physics.nist.gov/cuu/Units/.

3. Introduction to Engineering Experimentation, by Anthony J. Wheeler & Ahmad R.

Ganji, Pearson, 2010.

4. Process Control Instrumentation Technology, by Curtis D. Johnson, Pearson, 2014.
http://physics.nist.gov/cuu/Units/http://physics.nist.gov/cuu/Units/http://physics.nist.gov/cuu/Units/

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