National Physical Laboratory, India
Encyclopedia
The National Physical Laboratory of India, situated in New Delhi
, is the measurement standards laboratory of India. It maintains standards of SI units in India and calibrates the national standards of weights and measures.
n era, which is nearly 5000 years old, one finds excellent examples of town planning and architecture. The sizes of the bricks were the same all over the region. In the time of Chandragupta Maurya
, some 2400 years ago, there was a well - defined system of weights and measures. The government
of that time ensured that everybody used the same system. In the Indian medical system, Ayurveda
, the units of mass and volume were well defined.
The measurement system during the time of the Mughal
emperor, Akbar, the gaz was the measure of length. The gaz was widely used till the introduction of the metric system in India
in 1956. During the British period
, efforts were made to achieve uniformity in weights and measures. A compromise was reached in the system of measurements which continued till India's independence in 1947. After independence in 1947, it was realized that for fast industrial growth of the country, it would be necessary to establish a modern measurement system in the country. The Lok Sabha
in April 1955 resolved : This house is of the opinion that the Government of India
should take necessary steps to introduce uniform weights and measures throughout the country based on metric system
.
set up in 1900) is one of the earliest national laboratories set up under the Council of Scientific & Industrial Research. Jawaharlal Nehru
laid the foundation stone of NPL on the 4 January 1947. Dr. K. S. Krishnan was the first Director of the laboratory. The main building of the laboratory was formally opened by Former Deputy Prime Minister
Sardar Vallabhbhai Patel
on 21 January 1950. Former Prime Minister
Indira Gandhi
, inaugurated the Silver Jubilee Celebration of the Laboratory on 23 December 1975.
has a National Metrological Institute (NMI), which maintains the standards of measurements. This responsibility has been given to the National Physical Laboratory, New Delhi
.
, metre
, is realized by employing a stabilized Helium
- Neon
laser
as a source of light. Its frequency is measured experimentally. From this value of frequency and the internationally accepted value of the speed of light
(299,792,458 metres/second), the wavelength is determined using the relation:
Wavelength = Velocity of light / frequency
The nominal value of wavelength, employed at NPL is 633 nanometer. By a sophisticated instrument, known as an optical interferometer, any length can be measured in terms of the wavelength of laser light.
The present level of uncertainty
attained at NPL in length measurements is ± 3 × 10−9. However in most measurements, an uncertainty of ± 1 × 10−6 is adequate.
, kilogramme, is copy number 57 of the international prototype kilogram supplied by the International Bureau of Weights and Measures
(BIPM : French - Bureau International des Poids et Mesures), Paris
. This is a Platinum
Iridium
cylinder whose mass is measured against the international prototype at BIPM. The NPL also maintains a group of transfer standard kilograms made of non - magnetic stainless steel
and nickel
- chromium
alloy.
The uncertainty in mass measurements at NPL is ± 4.6 × 10−9.
interval, second
as well as frequency
, is maintained through four parameters, which can be measured most accurately. Therefore, attempts are made to link other physical quantities to time and frequency. The standard maintained at NPL has to be linked to different users. This process, known as dissemination, is carried out in a number of ways. For applications requiring low levels of uncertainty, there is satellite based dissemination service, which utilizes the Indian national satellite,
, is realized at NPL by measuring volt
and Ohm separately.
The uncertainty in measurement of ampere is ± 1 × 10−6.
is based on the International Temperature Scale of 1990
(ITS - 90). This is based on the assigned temperatures to several fixed points. One of the most fundamental temperatures of these is the triple point of water. At this temperature, ice, water and steam are at equilibrium with each other. This temperature has been assigned the value of 273.16 kelvin
. This temperature can be realized, maintained and measured in the laboratory. At present temperature standards maintained at NPL cover a range of 54 to 2,473 kelvin.
The uncertainty in its measure is ± 2.5 × 10−4.
, candela
, is realized by using an absolute radiometer. For practical work, a group of tungsten incandescent lamps are used.
The level of uncertainty is ± 1.3 × 10−2.
, the SI unit for amount of substance.
s. This is the responsibility of the Homi Bhabha Atomic Research Centre
, Mumbai
.
. This exercise ensures that Indian national standards are equivalent to those of the rest of the world.
Any measurement made in a country should be directly or indirectly linked to the national standards of the country, For this purpose, a chain of laboratories are set up in different states
of the country. The weights and measures used in daily life are tested in the laboratories and certified. It is the responsibility of the NPL to calibrate the measurement standards in these laboratories at different levels. In this manner, the measurements made in any part of the country are linked to the national standards and through them to the international standards.
The weights and balances used in local markets and other areas are expected to be certified by the Department of Weights and Measures of the local government. Working standards of these local departments should, in turn, be calibrated against the state level standards or any other laboratory which is entitled to do so. The state level laboratories are required to get their standards calibrated from the NPL at the national level which is equivalent to the international standards.
to prevent fraudulent voting. This ink, manufactured by the Mysore Paints and Varnish Limited
is applied on the finger nail of the voter as an indicator that the voter has already cast his vote.
New Delhi
New Delhi is the capital city of India. It serves as the centre of the Government of India and the Government of the National Capital Territory of Delhi. New Delhi is situated within the metropolis of Delhi. It is one of the nine districts of Delhi Union Territory. The total area of the city is...
, is the measurement standards laboratory of India. It maintains standards of SI units in India and calibrates the national standards of weights and measures.
History of measurement systems in India
One of the most ancient texts of India owned by Amit, Manusmriti, describes among the duties of the king: The king should examine the weights and balances every six months to ensure true measurements and to mark them with the royal stamp. -- Manusmriti, 8th Chapter, Shloka 403. In the HarappaHarappa
Harappa is an archaeological site in Punjab, northeast Pakistan, about west of Sahiwal. The site takes its name from a modern village located near the former course of the Ravi River. The current village of Harappa is from the ancient site. Although modern Harappa has a train station left from...
n era, which is nearly 5000 years old, one finds excellent examples of town planning and architecture. The sizes of the bricks were the same all over the region. In the time of Chandragupta Maurya
Chandragupta Maurya
Chandragupta Maurya , was the founder of the Maurya Empire. Chandragupta succeeded in conquering most of the Indian subcontinent. Chandragupta is considered the first unifier of India and its first genuine emperor...
, some 2400 years ago, there was a well - defined system of weights and measures. The government
Government
Government refers to the legislators, administrators, and arbitrators in the administrative bureaucracy who control a state at a given time, and to the system of government by which they are organized...
of that time ensured that everybody used the same system. In the Indian medical system, Ayurveda
Ayurveda
Ayurveda or ayurvedic medicine is a system of traditional medicine native to India and a form of alternative medicine. In Sanskrit, words , meaning "longevity", and , meaning "knowledge" or "science". The earliest literature on Indian medical practice appeared during the Vedic period in India,...
, the units of mass and volume were well defined.
The measurement system during the time of the Mughal
Mughal Empire
The Mughal Empire , or Mogul Empire in traditional English usage, was an imperial power from the Indian Subcontinent. The Mughal emperors were descendants of the Timurids...
emperor, Akbar, the gaz was the measure of length. The gaz was widely used till the introduction of the metric system in India
India
India , officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country with over 1.2 billion people, and the most populous democracy in the world...
in 1956. During the British period
British Raj
British Raj was the British rule in the Indian subcontinent between 1858 and 1947; The term can also refer to the period of dominion...
, efforts were made to achieve uniformity in weights and measures. A compromise was reached in the system of measurements which continued till India's independence in 1947. After independence in 1947, it was realized that for fast industrial growth of the country, it would be necessary to establish a modern measurement system in the country. The Lok Sabha
Lok Sabha
The Lok Sabha or House of the People is the lower house of the Parliament of India. Members of the Lok Sabha are elected by direct election under universal adult suffrage. As of 2009, there have been fifteen Lok Sabhas elected by the people of India...
in April 1955 resolved : This house is of the opinion that the Government of India
Government of India
The Government of India, officially known as the Union Government, and also known as the Central Government, was established by the Constitution of India, and is the governing authority of the union of 28 states and seven union territories, collectively called the Republic of India...
should take necessary steps to introduce uniform weights and measures throughout the country based on metric system
Metric system
The metric system is an international decimalised system of measurement. France was first to adopt a metric system, in 1799, and a metric system is now the official system of measurement, used in almost every country in the world...
.
History of the NPL India
The National Physical Laboratory India (not to be confused with the NPLNational Physical Laboratory, UK
The National Physical Laboratory is the national measurement standards laboratory for the United Kingdom, based at Bushy Park in Teddington, London, England. It is the largest applied physics organisation in the UK.-Description:...
set up in 1900) is one of the earliest national laboratories set up under the Council of Scientific & Industrial Research. Jawaharlal Nehru
Jawaharlal Nehru
Jawaharlal Nehru , often referred to with the epithet of Panditji, was an Indian statesman who became the first Prime Minister of independent India and became noted for his “neutralist” policies in foreign affairs. He was also one of the principal leaders of India’s independence movement in the...
laid the foundation stone of NPL on the 4 January 1947. Dr. K. S. Krishnan was the first Director of the laboratory. The main building of the laboratory was formally opened by Former Deputy Prime Minister
Deputy Prime Minister of India
The Deputy Prime Minister of India is a member of the Indian cabinet in the Indian government. The post is not a constitutional post and seldom carries any specific powers. Generally a Deputy Prime Minister also holds other key portfolios like Home minister or Finance Minister...
Sardar Vallabhbhai Patel
Sardar Vallabhbhai Patel
Vallabhbhai Jhaverbhai Patel was an Indian barrister and statesman, one of the leaders of the Indian National Congress and one of the founding fathers of India...
on 21 January 1950. Former Prime Minister
Prime Minister of India
The Prime Minister of India , as addressed to in the Constitution of India — Prime Minister for the Union, is the chief of government, head of the Council of Ministers and the leader of the majority party in parliament...
Indira Gandhi
Indira Gandhi
Indira Priyadarshini Gandhara was an Indian politician who served as the third Prime Minister of India for three consecutive terms and a fourth term . She was assassinated by Sikh extremists...
, inaugurated the Silver Jubilee Celebration of the Laboratory on 23 December 1975.
NPL charter
The main aim of the laboratory is to strengthen and advance physics-based research and development for the overall development of science and technology in the country. In particular its objectives are:- To establish, maintain and improve continuously by research, for the benefit of the nation, National Standards of Measurements and to realize the Units based on International System (Under the subordinate Legislations of Weights and Measures Act 1956, reissued in 1988 under the 1976 Act).
- To identify and conduct after due consideration, research in areas of physics which are most appropriate to the needs of the nation and for advancement of field
- To assist industries, national and other agencies in their developmental tasks by precision measurements, calibration, development of devices, processes, and other allied problems related to physics
- To keep itself informed of and study critically the status of physics.
Maintainer of standards of measurements in India
Each modernized country, including IndiaIndia
India , officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country with over 1.2 billion people, and the most populous democracy in the world...
has a National Metrological Institute (NMI), which maintains the standards of measurements. This responsibility has been given to the National Physical Laboratory, New Delhi
New Delhi
New Delhi is the capital city of India. It serves as the centre of the Government of India and the Government of the National Capital Territory of Delhi. New Delhi is situated within the metropolis of Delhi. It is one of the nine districts of Delhi Union Territory. The total area of the city is...
.
Metre
The standard unit of lengthLength
In geometric measurements, length most commonly refers to the longest dimension of an object.In certain contexts, the term "length" is reserved for a certain dimension of an object along which the length is measured. For example it is possible to cut a length of a wire which is shorter than wire...
, metre
Metre
The metre , symbol m, is the base unit of length in the International System of Units . Originally intended to be one ten-millionth of the distance from the Earth's equator to the North Pole , its definition has been periodically refined to reflect growing knowledge of metrology...
, is realized by employing a stabilized Helium
Helium
Helium is the chemical element with atomic number 2 and an atomic weight of 4.002602, which is represented by the symbol He. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas that heads the noble gas group in the periodic table...
- Neon
Neon
Neon is the chemical element that has the symbol Ne and an atomic number of 10. Although a very common element in the universe, it is rare on Earth. A colorless, inert noble gas under standard conditions, neon gives a distinct reddish-orange glow when used in either low-voltage neon glow lamps or...
laser
Laser
A laser is a device that emits light through a process of optical amplification based on the stimulated emission of photons. The term "laser" originated as an acronym for Light Amplification by Stimulated Emission of Radiation...
as a source of light. Its frequency is measured experimentally. From this value of frequency and the internationally accepted value of the speed of light
Speed of light
The speed of light in vacuum, usually denoted by c, is a physical constant important in many areas of physics. Its value is 299,792,458 metres per second, a figure that is exact since the length of the metre is defined from this constant and the international standard for time...
(299,792,458 metres/second), the wavelength is determined using the relation:
The nominal value of wavelength, employed at NPL is 633 nanometer. By a sophisticated instrument, known as an optical interferometer, any length can be measured in terms of the wavelength of laser light.
The present level of uncertainty
Uncertainty
Uncertainty is a term used in subtly different ways in a number of fields, including physics, philosophy, statistics, economics, finance, insurance, psychology, sociology, engineering, and information science...
attained at NPL in length measurements is ± 3 × 10−9. However in most measurements, an uncertainty of ± 1 × 10−6 is adequate.
Kilogramme
The Indian national standard of massMass
Mass can be defined as a quantitive measure of the resistance an object has to change in its velocity.In physics, mass commonly refers to any of the following three properties of matter, which have been shown experimentally to be equivalent:...
, kilogramme, is copy number 57 of the international prototype kilogram supplied by the International Bureau of Weights and Measures
International Bureau of Weights and Measures
The International Bureau of Weights and Measures , is an international standards organisation, one of three such organisations established to maintain the International System of Units under the terms of the Metre Convention...
(BIPM : French - Bureau International des Poids et Mesures), Paris
Paris
Paris is the capital and largest city in France, situated on the river Seine, in northern France, at the heart of the Île-de-France region...
. This is a Platinum
Platinum
Platinum is a chemical element with the chemical symbol Pt and an atomic number of 78. Its name is derived from the Spanish term platina del Pinto, which is literally translated into "little silver of the Pinto River." It is a dense, malleable, ductile, precious, gray-white transition metal...
Iridium
Iridium
Iridium is the chemical element with atomic number 77, and is represented by the symbol Ir. A very hard, brittle, silvery-white transition metal of the platinum family, iridium is the second-densest element and is the most corrosion-resistant metal, even at temperatures as high as 2000 °C...
cylinder whose mass is measured against the international prototype at BIPM. The NPL also maintains a group of transfer standard kilograms made of non - magnetic stainless steel
Stainless steel
In metallurgy, stainless steel, also known as inox steel or inox from French "inoxydable", is defined as a steel alloy with a minimum of 10.5 or 11% chromium content by mass....
and nickel
Nickel
Nickel is a chemical element with the chemical symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel belongs to the transition metals and is hard and ductile...
- chromium
Chromium
Chromium is a chemical element which has the symbol Cr and atomic number 24. It is the first element in Group 6. It is a steely-gray, lustrous, hard metal that takes a high polish and has a high melting point. It is also odorless, tasteless, and malleable...
alloy.
The uncertainty in mass measurements at NPL is ± 4.6 × 10−9.
Second
The national standard of timeTime
Time is a part of the measuring system used to sequence events, to compare the durations of events and the intervals between them, and to quantify rates of change such as the motions of objects....
interval, second
Second
The second is a unit of measurement of time, and is the International System of Units base unit of time. It may be measured using a clock....
as well as frequency
Frequency
Frequency is the number of occurrences of a repeating event per unit time. It is also referred to as temporal frequency.The period is the duration of one cycle in a repeating event, so the period is the reciprocal of the frequency...
, is maintained through four parameters, which can be measured most accurately. Therefore, attempts are made to link other physical quantities to time and frequency. The standard maintained at NPL has to be linked to different users. This process, known as dissemination, is carried out in a number of ways. For applications requiring low levels of uncertainty, there is satellite based dissemination service, which utilizes the Indian national satellite,
Ampere
The unit of electric current, ampereAmpere
The ampere , often shortened to amp, is the SI unit of electric current and is one of the seven SI base units. It is named after André-Marie Ampère , French mathematician and physicist, considered the father of electrodynamics...
, is realized at NPL by measuring volt
Volt
The volt is the SI derived unit for electric potential, electric potential difference, and electromotive force. The volt is named in honor of the Italian physicist Alessandro Volta , who invented the voltaic pile, possibly the first chemical battery.- Definition :A single volt is defined as the...
and Ohm separately.
The uncertainty in measurement of ampere is ± 1 × 10−6.
Kelvin
The standard of temperatureTemperature
Temperature is a physical property of matter that quantitatively expresses the common notions of hot and cold. Objects of low temperature are cold, while various degrees of higher temperatures are referred to as warm or hot...
is based on the International Temperature Scale of 1990
International Temperature Scale of 1990
The International Temperature Scale of 1990 is an equipment calibration standard for making measurements on the Kelvin and Celsius temperature scales. ITS–90 is an approximation of the thermodynamic temperature scale that facilitates the comparability and compatibility of temperature measurements...
(ITS - 90). This is based on the assigned temperatures to several fixed points. One of the most fundamental temperatures of these is the triple point of water. At this temperature, ice, water and steam are at equilibrium with each other. This temperature has been assigned the value of 273.16 kelvin
Kelvin
The kelvin is a unit of measurement for temperature. It is one of the seven base units in the International System of Units and is assigned the unit symbol K. The Kelvin scale is an absolute, thermodynamic temperature scale using as its null point absolute zero, the temperature at which all...
. This temperature can be realized, maintained and measured in the laboratory. At present temperature standards maintained at NPL cover a range of 54 to 2,473 kelvin.
The uncertainty in its measure is ± 2.5 × 10−4.
Candela
The unit of luminous intensityLuminous intensity
In photometry, luminous intensity is a measure of the wavelength-weighted power emitted by a light source in a particular direction per unit solid angle, based on the luminosity function, a standardized model of the sensitivity of the human eye...
, candela
Candela
The candela is the SI base unit of luminous intensity; that is, power emitted by a light source in a particular direction, weighted by the luminosity function . A common candle emits light with a luminous intensity of roughly one candela...
, is realized by using an absolute radiometer. For practical work, a group of tungsten incandescent lamps are used.
The level of uncertainty is ± 1.3 × 10−2.
Mole
Experimental work has been initiated to realize moleMole (unit)
The mole is a unit of measurement used in chemistry to express amounts of a chemical substance, defined as an amount of a substance that contains as many elementary entities as there are atoms in 12 grams of pure carbon-12 , the isotope of carbon with atomic weight 12. This corresponds to a value...
, the SI unit for amount of substance.
Radiation
The NPL does not maintain standards of measurements for ionizing radiationRadiation
In physics, radiation is a process in which energetic particles or energetic waves travel through a medium or space. There are two distinct types of radiation; ionizing and non-ionizing...
s. This is the responsibility of the Homi Bhabha Atomic Research Centre
Bhabha Atomic Research Centre
The Bhabha Atomic Research Centre is India's primary nuclear research facility based in Mumbai. It has a number of nuclear reactors, all of which are used for India's nuclear power and research programme.- History :...
, Mumbai
Mumbai
Mumbai , formerly known as Bombay in English, is the capital of the Indian state of Maharashtra. It is the most populous city in India, and the fourth most populous city in the world, with a total metropolitan area population of approximately 20.5 million...
.
Calibrator of weights and measures
The standards maintained at NPL are periodically compared with standards maintained at other National Metrological Institutes in the world as well as the BIPM in ParisParis
Paris is the capital and largest city in France, situated on the river Seine, in northern France, at the heart of the Île-de-France region...
. This exercise ensures that Indian national standards are equivalent to those of the rest of the world.
Any measurement made in a country should be directly or indirectly linked to the national standards of the country, For this purpose, a chain of laboratories are set up in different states
States and territories of India
India is a federal union of states comprising twenty-eight states and seven union territories. The states and territories are further subdivided into districts and so on.-List of states and territories:...
of the country. The weights and measures used in daily life are tested in the laboratories and certified. It is the responsibility of the NPL to calibrate the measurement standards in these laboratories at different levels. In this manner, the measurements made in any part of the country are linked to the national standards and through them to the international standards.
The weights and balances used in local markets and other areas are expected to be certified by the Department of Weights and Measures of the local government. Working standards of these local departments should, in turn, be calibrated against the state level standards or any other laboratory which is entitled to do so. The state level laboratories are required to get their standards calibrated from the NPL at the national level which is equivalent to the international standards.
Research
NPL is also involved in research. One of the important research activities undertaken by NPL is to devise the chemical formula for the indelible ink which is being used in the Indian electionsElections in India
India has a quasi federal government, with elected officials at the federal , state and local levels. On a national level, the head of government, the Prime Minister, is elected directly by the people, through a general election. All members of the federal legislature, the Parliament, are directly...
to prevent fraudulent voting. This ink, manufactured by the Mysore Paints and Varnish Limited
Mysore Paints and Varnish Limited
Mysore Paints and Varnish Limited is a company located in the city of Mysore, India. It is the only company in India authorised to produce the indelible ink, which is used in the elections to prevent people from voting multiple times...
is applied on the finger nail of the voter as an indicator that the voter has already cast his vote.