On November 16, 2018, the General Conference on Weight and Measures approved the redefinition of the International System of Units (SI).
This changed the world’s definition of the kilogramme (a unit of mass), the ampere (a unit of electric current), the kelvin (a unit of temperature) and the mole (a unit for measuring the amount of substance in a solution).
The application of the changes took effect from May 20, the World Metrology Day that is celebrated annually all over the world. This year’s theme, “The International System of Units – fundamentally better,” recognises the work behind the newly revised SI.
The science of measurement and its application, also commonly referred to as metrology, is an essential aspect in promoting and sustaining economic development, as well as environmental and social wellbeing.
It is vital in many aspects of development ranging from ensuring that traders receive the correct payment for their commodities and consumers the correct quantity of goods paid for; to ensuring accurate medical measurements for prevention, diagnoses and treatment of diseases.
Accurate measurement is important in determining the value of aspects that may range from climate change variables; to establishing trucks axle loads to prevent overloading and generally enhancing the confidence among a country’s citizens and its trading partners in the quality of its manufacturing and services.
There are seven base units under the International System of Units (SI) that have been accepted for all applications of measurement worldwide. These include the second, the metre, the kilogramme, the ampere, the kelvin, the mole and the candela. From these SI units, there are several derived units. These form the basis on which all measurements are carried out.
The implementation of the revised SI ushers in a new era of non-reliance on physical and technological artifacts for precision measurements. To date, the kilogramme has been defined based on the weight of a platinum mass that has been stored in Paris since 1889. After the revision , the kilogramme will be defined in terms of an electric current.
The redefinition is based on physical constants of nature, which are inherently stable compared to material artefacts and so for the first time, measurements will accurately be defined by nature’s fundamental laws.
This marks an important step forward, just as the redefinition of the second brought about the Global Positioning System (GPS) navigation did.
The revision ensures that the international measurement system is not only robust and able to stand the test of time but able to effectively support future advances in science and technology.
In addition, the redefined SI will enable technologies we have yet to imagine, whilst maintaining continuity for the practical users.
However, for most, it will appear that not much has changed. The changes will impact a small number of high level electrical calibration services, but most customers using calibration services can anticipate a negligible impact.
Companies using measurement and calibration services can also expect a seamless transition.
The writer is head of testing at the Kenya Bureau of Standards.