Simply stated, metrology is the science of measurement. Everything that has to do with measurement, be it designing, conducting, or analysing the results of a test, exists within the metrology realm. These things cover the range from the abstract, comparing statistical methods, for example, to the practical, such as deciding which scale of a ruler to read. It is a broad field and as will be seen, more things can be grouped as metrology-related as might be thought of at first.
A Metrologist can perform various functions that at first may seem not to have anything to do with measurement. Statistical analysis, database building, and writing automation programs are a few examples. But in today’s metrology laboratory, these things have everything to do with metrology. In addition, designing measurement tests, analyzing the results, determining the final accuracy of the device under test, and, perhaps the most important part of metrology, calibration, are all things that a Metrologist may do.
It covers three main tasks:
- Definition of internationally accepted units of measurement, the metre, for example.
- Realisation of units of measurement by scientific methods, for instance, the metre through laser beams.
- Establishment of Traceability chains in documenting accuracy of a measurement, documenting the relationship between the micrometer (metre) and primary laboratory (highest level of accuracy )for optical length (laser beams).
Basically, there are three categories, three different levels of complexity and accuracy namely scientific metrology, industrial metrology and legal metrology.
This deals with the organisation and development of measurement standards and their maintenance at the highest level. There are 9 technical subjects within the BIPM (the international Bureau of Weights and measures, the international metrology regulatory body), 4 of which constitute the metrology department at ZABS. These include mass (and its related quantities of force, preasure, volume and density), electricity, length and thermometry. Various standards are maintained at ZABS in these fields: the national standards for mass, voltage and resistance, length, temperature, pressure and volume,
all disseminated through calibration of measurement equipment. All the labs at ZABS are at the highest metrology level in the country and as such, all measurements in the country are ideally supposed to get their traceability from ZABS.
On the Zambian scenario, this is the level directly below scientific metrology. Mainly, industrial metrology ensures the adequate functioning of measurement instruments used in industry, in production and testing processes which is done through calibration. This is simply the comparison of a measurement device (an unknown) against an equal or better standard which is considered to be the reference and taken to be the more accurate of the two. This is done to find out how far the unknown is from the standard. Thus this
(a) ensures that readings from the instrument are consistent with other measurements,
(b) determines the accuracy of the instrument’s reading as well as
(c) establishes the reliability of the instrument, that is, it can be trusted.
As can be seen, the quality aspects of production are heavily reliant on reliable measurements.
Though not mandated to do so, it is expedient that all measurement equipment used in industry is calibrated to ensure customer satisfaction and safety as well as meet international export requirements giving credibility to local products on the international market.
Legal metrology originated from the need to ensure fair trade, specifically in the area of weights and measures. Legal metrology is primarily concerned with measuring instruments which are themselves legally controlled. The main objective of legal metrology is to ensure citizens of correct measurements results when used
- In official commercial transactions
- In labour environments, health and safety.
The international Organisation of Legal Metrology (OIML) is the body in charge of all regulations in this category of metrology and in Zambia, the Zambia Weights and Measures (ZWMA) is the statutory body in legal metrology. There are also many other areas of legislation, outside legal metrology, where measurements are required to assess conformance with regulations: aviation, environmental and pollution control to mention but a few.
What metrology means
The effects of the science of measurements can be seen everywhere, allowing people to plan their lives and make commercial exchanges with confidence. For example, most people can assume that clocks in their homes and clocks in their work places all display
approximately the same time. It is expected that a pound of hamburger purchased from one grocery store will contain the same quantity of food at a store across town. And a screw purchased from company A will fit into a hole made by a drill purchased from company B, assuming they are specified to the same size.
Most people also trust that the speedometers in their cars will measure speed the same as the local police’s; that 14 karat gold jewellery contains the appropriate amount of gold; that the 2kg of sugar from purchased will contain just that, 2kg, and the temperatures indicated by thermostats, ovens, and thermometers are correct. Life would get complicated and in some cases, more dangerous, without proper measurements
Most people don’t need to know about the detailed aspects of metrology – as long as things continue to be measured correctly. However, that this article did shed some significant light on this otherwise ‘darkened’ subject.