Accurate and precise measurements Essential for scientific discoveries, regulation & manufacturing of high quality products
G’nY. Could you tell us about the brief history of the National Physical Laboratory (NPL) and its international equivalence?
D K Aswal : NPL was formed on January 4, 1947, and uniquely mandated to be the measurement standards laboratory of India. According to the core mandate, NPL’s role is to develop primary/national standards of the International System of Units (SI units) in India at par with the international level and disseminate them to academia and scientific, industrial and strategic sectors for their growth. Sir K S Krishnan was the first director of the NPL and I am fortunate to be the eleventh director of this prestigious lab.
NPL was formally opened by former Deputy Prime Minister Sardar Vallabhbhai Patel on January 21, 1950, and an account of this ceremony is published in March 24, 1951 issue of Nature. The inaugural ceremony of NPL was attended by a number of eminent people from many countries. It is apparent that the world had very high expectations from NPL-India.
The government of India—through NPL—is a permanent member of The General Conference on Weights and Measures (Conférence Générale des Poids et Mesures, CGPM), which has 59 member states and observers from 43 associate states and economies. This treaty founded the International Bureau of Weights and Measures (Bureau International des Poids et Mesures, BIPM) at Pavillon de Breteuil in Sèvres, France, through which National Metrology Institutes (NMIs) of member states and associate states act together on matters related to measurement science and measurement standards. The directors of NMIs of member states and associate states meet once a year at BIPM to discuss the developments on SI units and their dissemination for improving the quality of life. BIPM, therefore, provides the basis for a single, coherent system of measurements traceable to SI units throughout the world.
G’nY. SI units are now being revised. Can you tell us what would it be like and what are the expected implications?
D K Aswal : The proposal by International Committee for Weights and Measures (Comité international des poids et mesures, CIPM) summarises that there will still be the same seven base units (second, metre, kilogram, ampere, kelvin, mole and candela). Of these, the kilogram, ampere, kelvin, and mole will be redefined by choosing exact numerical values for the Planck constant (h), the elementary electric charge (e), the Boltzmann constant (k), and the Avogadro constant (NA) respectively. The Metre and candela are already defined by physical constants, i.e., speed of light (c), hyperfine splitting frequency of the caesium-133 atom, (∆v(133Cs)hfs), and luminous efficacy (Kcd), respectively. The new definitions will improve the SI units without changing the size of any of them, thus ensuring continuity with the present measurements. This will mean, amongst other things, that the prototype kilogram will cease to be used as the definitive replica of the kilogram. These accurate definitions of SI units will make advancements in the new science based on the quantum phenomena.
G’nY. How does NPL contribute to the scientific, industrial and economic growth of the country?
D K Aswal : The NMIs, like NPL for India, are the growth engines of nations. This is because accurate and precise measurements are required for scientific discoveries and regulation for manufacturing high-quality products. NPL supports more than 2,000 industries every year by providing apex calibration so that industrial equipments provide correct measurements for manufacturing quality products. It also collaborates with major government and semi-government organisations. In addition, NPL supports SAARC nations in enhancing their measuring capabilities.
G’nY. NPL is also the time-keeper of the nation. What does accuracy of time mean? How is it generated and what is its importance for a country like India?
D K Aswal : The SI unit of time is second which corresponds to 9192631770 oscillations between doubly splitted hyperfine ground states of 133Cs atoms at 0 K temperature. BIPM, France maintains the international time scales i.e. International Atomic Time (TAI) through a weighted average of nearly 450 atomic clocks operated by various NMIs worldwide (8 of them are from NPL-India). The Coordinated Universal Time (UTC) is derived from TAI by the application of an integral number of seconds that compensate for the irregular rate of rotation of the Earth, known as leap seconds. The Indian Standard Time (IST) is generated by NPL with an uncertainty of 7 nano-seconds with respect to UTC over a period of one day. NPL is disseminating IST to Indian Space Research Organisation (ISRO) for an indigenous GPS system.
In most developed nations, local time has been assigned as the legal time through legislation. However, this is not the case with IST yet. Clock synchronisation to national time is very important in computer networks and engineering sectors that aim to coordinate otherwise independent clocks. Even if clocks are initially set accurately, they will differ after some amount of time due to clock drift, which can cause several problems. Clock synchronisation implies clock recovery through synchronisation with accurate primary reference clocks.
Time synchronisation of clocks/devices to IST would benefit various sectors of national importance such as the strategic sectors, navigation, digital archiving, trade, weather prediction and disaster management, transportation, power grid application and various others. The applications of clock synchronisation to IST are unlimited, and if achieved, it will catalyse the growth and security of the country.
G’nY. Is NPL also working on the measurement of Air Quality Index? This is important as frightening numbers on air quality reported by various agencies have created fear among common people.
D K Aswal : Indeed, NPL is working on Air Quality Index (AQI) in collaboration with the Central Pollution Control Board (CPCB), Ministry of Environment, Forest and Climate Change, Government of India. Air pollution really is a major concern in many Indian cities and the government is taking various steps to improve the air quality management, which also includes strengthening the monitoring (both on-line continuous and manual) network. India has recently started shifting towards real-time Continuous Ambient Air Quality Monitoring (CAAQM) regime. However, manual sampling and analyses are also necessary to achieve the target as specified in the National Ambient Air Quality Standards (NAAQS), 2009. In developed countries, for deployment of reliable and certified air quality analysers or samplers, they have specific certification/approval programmes. India lacks in its own certification/approval system. Now Ministry of Environment, Forest and Climate Change has entrusted this responsibility to NPL. To begin with, NPL has already setup the country’s first wind tunnel facility that will calibrate the equipment that measures the Particulate Matter (PM1, PM2.5, PM10). For calibration of other air parameters and industrial emission, NPL has already planned and expects to get it completed in next two years.
G’nY. India imports most of the equipments required for harnessing solar energy, which often degrade faster than expected. What steps should the country take to ensure import of appropriate quality of solar panels as well as domestic manufacturing of quality solar panels?
D K Aswal : The Ministry of New and Renewable Energy (MNRE), Government of India, has a Mission of generating 100 GW solar energy by 2022. Majority of the imported solar panels have a warranty of 25 years. The stability of PV modules for 25 years (with 80 per cent of peak power requires) demands the degradation rate to be less than 0.8 per cent annually. However, a study of IIT-Bombay and MNRE for the year 2016 revealed that the degradation rate is more than two per cent, indicating that the life of panels is reduced to less than 10 years. This not only makes achieving 100 GW net solar capacity a distant dream but also creates huge waste in the immediate future that will be difficult to dispose.
One of the reasons for this is the lack of quality infrastructure in the country. This means that we do not have capability to test the panels as per our requirements before they are imported. This requires creation of a primary standard for accurate and precise measurements of the various parameters of solar cells/panels. Moreover, a greater number of test centres with ensured measurement traceability should be established across the country on which NPL has now started working in collaboration with MNRE. With the establishment of precise and accurate test centres, the parity between imported and indigenously manufactured solar panels can be achieved.
G’nY. What are Certified Reference Materials (CRMs) and how do they ensure the quality of various products like petroleum gold and cement in
D K Aswal : CRMs are very important for the production of quality products. CRMs are controls or standards which are used (i) to calibrate the measuring instruments, (ii) to validate analytical measurement methods, and (iii) to check the quality and metrological traceability of products. Majority of the CRMs needed for the production of high-quality products like petroleum, coal, metals and alloys, gases, cement, food, soil, water, etc. are currently imported. NPL has started the production of CRMs under the trademark name of Bhartiya Nirdeshak Dravya (BND) which
will help Indian industries to make their products at par with international quality.