Measurement

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MEASUREMENT IN SCIENCE AND TECHNOLOGY ___________________________________________________________________________________

What is Metrology? Metrology is the science of measurement. It is a branch of science in which measurement is studied scientifically. Definitions of the units, their well accepted standards of standardized measures used in science and technology are studied in metrology. What is Measurement? Process of determining magnitude of a given quantity in terms of a standard unit is known as measurement. Any quantity is made up of two parts (1) The number which shows how many times is the measurement when compared to the standard unit. (2) A unit which always follows the number indicating the measure. What is a Unit A trustworthy, definite, universally accepted standard measure is known as a unit of the quantity. Various systems of Units for measurement Unit System FPS System(British System) CGS System MKS System (Metric System) MKSA System (George System)

Fundamental Quantities Length , mass, time Length , mass, time Length , mass, time

Fundamental units Foot, pound, second Centimetre, gram, second Metre, kilogram, second

Length , mass, time, electric current

Metre, kilogram, second, ampere

Characteristics of a unit (1) Measure of a standard unit should be invariant in all conditions. (2) Unit should be defined on scientific basis. (3) Unit and its measure should be trustworthy and universally acceptable. (4) A copy of the standard measure of the unit should be easily reproducible. (5) Accurate measurement should be possible by the unit. (6) Unit should not be ambiguous (7) Unit should be user friendly. (8) Unit should be based on a system in which conversions are easy. Need of universal system of measurement (1) (2) (3) (4) (5) (6) (7) (8)

For development of science and technology For accuracy and uniformity in scientific research For solving the mysteries of nature For manufacturing efficient machines and their tiny parts For carrying out international trade easily For easy comparison. For getting rid of complicated and boring calculation For using machines made in different countries.

International system of units International system of units was accepted in 1971 by the 14 th General conference on weights and measures under the leadership of International Bureau of Weights and Measures situated at, Sevrs nears Paris. In French it is called Le Systeme internationale d’unites. So in short it is called SI system. There are Seven fundamental quantities in SI system of units. In SI system of units PLANE ANGLE, SOLID ANGLE and RADIOACTIVITY are accepted as supplementary quantities. Their units are known as supplementary units. They are radian (rad), steradian (sr) and curie (ci) SI UNIT SYSTEM No. 1 2 3 4 5 6 7

Fundamental quantity Length Mass Time Electric current Thermodynamic temperature Luminous intensity Quantity of matter

Fundamental unit Metre Kilogram Second Ampere Kelvin Candela Mole

Symbol m kg s A K cd mol

Guidelines for using symbols for SI units 1. All the symbols use small alphabets only, unless the unit is named after a scientist. Symbols should be written “upright type” only not in italics Unit Metre Kilogram

Wrong method M, m KG, Kg, kg

Correct method m kg

2. Description can be in any language like Gujarati, Hindi, English, Russian etc. but magnitude of the quantity should be written in international system of numbers and unit should be mentioned as the unit of SI system only. Measure of quantitiy 40 metre 5 kilometre

Wrong method 40m , 5km,

Correct method 40 m 5 km

3. Unit should not be written in plural. It is always in singular form. 4. “Full stop” should not be put between the letters of symbol or at the end of the symbol. Unit Centimeter Kilogram

Wrong method c.m., cm. k.g., kg.

Correct method cm kg

5. If the unit, named after a scientist is written fully its first letter should not be capital. If its symbol is used its first letter is written in capital. Unit Force Temperature

Wrong method Newton, n Kelvin , k

Correct method newton, N kelvin, K

6. In case of a derived unit which is a ratio of two base units, oblique line (/) or horizontal line (-) or negative power can be used. e.g. m / s, m-s, m s-1 7. Quantities appearing in numerator and denominator in a derived unit should be expressed as a single ratio. Some space between symbols of two units is to be kept. Derived Unit Velocity Acceleration

Wrong method m/s, ms-1 m/s2, ms-2,m/s/s

Correct method m / s, m s-1 m / s2, m s-2

8. In a derived unit if more than one base unit is written, either write their full forms or symbols. Don’t write full form of one and the symbol of the other. Derived Unit Momentum

Wrong method kg metre/s

Correct method kg m/s

Decimal Multiples used with SI unit Decimal multiple 24

10 1021 1018 1015 1012 109 106 103 102 10

Prefix yotta zetta exa peta tera giga mega kilo hecto decca

Symbol Y Z E P T G M K H Da

Decimal Submultiples used with SI unit Decimal Sub multiple 10-1 10-2 10-3 10-6 10-9 10-12 10-15 10-18 10-21 10-24

Prefix deci centi milli micro nano pico femto atto zepto yocto

Symbol d c m µ n p f a z y

Guide lines of using Prefix. (1) Prefix alone is never used. Prefix is always written along with unit and before unit. (2) Only the assigned symbols should be used for the prefixes and the letter of symbol is to be written upright only. (3) No gap should be kept between symbols of prefix and unit.