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Australian Government: National Measurement InstituteAustralian Government: National Measurement Institute
National Measurement Institute

How Australia's Measurement System Works

Australia has a well-developed standards and conformance infrastructure which is made up of four national organisations (and complemented by legal metrology authorities). The national organisations are:

In March 2010 these four organisations established a new body – the Technical Infrastructure Alliance – to identify and execute joint projects with the aim of bringing greater efficiency and performance in quality standards. 

Australian Legal Units of Measurement

The national measurement system is a coherent formal system which ensures that measurements can be made on a consistent basis throughout the country. It ensures that practical measurements made by industry and the community are linked to the International System of Units (SI). SI units were adopted by international agreement at the General Conference of Weights and Measures in 1960 and they form the basis of Australia’s hierarchy of standards. SI units are divided into two classes: base units and derived units.

The National Measurement Act prescribes that 'Australian legal units of measurement of a physical quantity are the sole legal units of measurement of that physical quantity' and Schedules 1, 2 and 3 of the National Measurement Regulations prescribe those Australian legal units of measurement, namely:

  • SI base units of measurement (kilogram, mole, metre, second, candela, kelvin and ampere) – Schedule 1, Part 1
  • SI derived units of measurement with special names – Schedule 1, Part 2
  • non-SI units of measurement used with SI units of measurement – Schedule 1, Part 3
  • additional derived units of measurement – Schedule 1, Part 4 
  • additional legal units of measurement (and the purposes for which they may be used) – Schedule 2, Parts 1 and 2 

SI prefixes which can be used to form decimal multiples and submultiples of SI units are prescribed in Schedule 3 of the Regulations and the National Measurement Guidelines prescribe the way in which units of measurement and prefixes may be combined to produce an Australian legal unit of measurement.

Pyramid showing the hierarchy of standardsThe hierarchy of standards by which a physical measurement can be related back through the national metrological pyramid to the relevant SI unit is known as traceability. The National Measurement Act requires NMI or its agents to maintain such standards of measurement that are necessary to provide means for measurements of physical quantities to be made in terms of the legal units.

Note: The SI unit of measurement of chemical quantities is the mole. However there is no internationally agreed realisation or prototype of the mole and so traceability is usually achieved by the use of tools such as certified reference materials and reference methods.

International traceability is achieved by collaborating with both national standards laboratories of other scientifically advanced nations and the International Bureau of Weights and Measures through comparisons of national standards. These comparisons provide confidence in the consistency of the international measurement system. In addition NMI has a number of bilateral agreements with other countries on equivalence of national standards.

First-level Standards

Legal units of measurement have to be realised as tangible practical standards of measurement in order to be useful. NMI is responsible for realising, maintaining and disseminating Australia’s national physical standards.

NMI maintains a national (or Australian primary) standard for each of the SI base units except the ampere (which is derived from standards of voltage and resistance) and the mole (for which no internationally-defined realisation has been developed as yet). NMI also maintains Australian primary standards for a wide range of derived units.

The primary standards for the SI base units and derived units are not always easy to work with. For that reason, NMI also holds Australian secondary standards (calibrated in terms of the primary standards) which are more convenient to use when calibrating lower-level standards or instruments.

NMI is also responsible for developing and maintaining certified reference materials and reference methods which underpin consistency of chemical measurements.

NMI has delegated responsibility for maintaining standards relating to ionising radiation to the Australian Nuclear Science and Technology Organisation and the Australian Radiation Protection and Nuclear Safety Agency.

Second and Third-level Standards

It would be impractical for NMI to handle all of the measuring standards and instruments that require calibration in order to demonstrate traceability of measurement. Therefore NMI calibrates higher accuracy standards held by government calibration laboratories, verifying authorities and private sector calibration laboratories accredited by NATA. These second-level laboratories calibrate a wide range of lower accuracy standards and measuring instruments used in industry and commerce.