Measurement is the process of obtaining the magnitude of a quantity relative to an agreed standard. The articles we have on measurement focus on the agreed standards of measurement in use in New Zealand.

SI units

Measurement of any quantity involves comparison with some precisely defined unit value of the quantity. Standard units of measure need to be identified and defined as accurately as possible. The system that is used in the scientific community is called Système International d’Unités, abbreviated to SI.

All of the SI units used in scientific measurements can be derived from just seven fundamental standards called base units. Apart from mass, each of these units has a definition based on an unchanging property of nature. SI derived units come from multiplying, dividing or powering the base units in various combinations. A significant number of SI derived units have been named in honour of individuals who did ground-breaking work in science.

The International Bureau of Weights and Measures (BIPM) has guidelines on how to properly use and apply the SI units. Expressing quantities describes how unit symbols and names should be written and used and how the values of quantities should be expressed. Powers of 10 explains the prefix names and symbols for decimal multiples and submultiples of SI units.

Issues with the mass standard

Of the seven base SI units, mass is the only one still defined by a material artefact – a metal cylinder made in the 1880s. Changing the mass standard highlights the need to move from the artefact to a fundamental physical constant. Dr Laurie Christian and Dr Chris Sutton, scientists with the New Zealand Measurement Standards Laboratory, have developed a novel research approach to the international development of a new mass standard.

The SI units will be revised in 2018 and will no longer rely on artefacts to derive the mass unit.

The history of measurement

The SI system standardised international measurement systems. Read about earlier measurement systems – from the Babylonians to more recent European systems. Māori had their own measurement standards for building, carving and weaving.

Take up the challenge

The student activities covering measurement range from quirky to precise. Measurements, weird and wonderful is a collection of unusual measurement units – such as a moment (1/40 of an hour). Follow this up with Cubits, spans and digits to reinforce the degree of uncertainty when using non-SI measurements.

Measuring foot pressure provides practice using SI units, derived units and prefixes. Precision and accuracy provides various data sets for students to judge precision and accuracy in scientific settings. How long is it? is a collection of length measurements found within the Science Learning Hub. Lengths range from the very small to the very big, helping students develop an understanding of the decimal system as applied to length measurement.

Useful link

The International Bureau of Weights and Measures (BIPM) website has information on the revision of SI units.

 

Published 17 August 2011