Measurement

Measurement, while common to nearly everyone, is actually a scientific technology that includes methods, devices, standards and a wide range of sub-technologies when looked at in detail. Most people are familiar with activities like measuring physical dimensions, like length or area or volume, or more complex variables like time and temperature, but there’s much, much more to it than that.

The science of measurement is called “Metrology”, or, sometimes, “Measurement Science” (not too original). It deals with the calibration of measuring devices and the statistical methods used in determining the bias, precision and uncertainty of measurements under defined conditions, such as in a laboratory environment.

It also encompasses the use of measuring devices under less than ideal conditions, such as found in a factory or outdoors environment, or the “real world”(as some call those places).

Some think that metrologists (not meteorologists – they deal with weather forecasting) do only calibration.

Not so. They do lots more, but usually no weather forecasting.

Measurement science gets into more mathematics and involved detail than the average person wants to know. But, if you are curious, or just interested in details, you can get a better appreciation of measurement without knowing much math.

Know that measurement deals with the properties of an object and enables those who measure carefully to make meaningful or substantial statements about those properties. (Quiet thanks to the late Lord Raleigh).

It’s very important stuff to understand in detail if you are in the metrology business or drawing inferences or make important decisions based on, or from, them.

It’s also good general knowledge to appreciate measurement as a cornerstone of science, engineering and our very way of life in the civilized world.

* Why measure in the first place?

Perhaps this little page will help put it in some better perspective.

* Units of Measurement The SI system of units (Meters, Kilograms, Seconds, Celsius, etc.) is the common, defined vocabulary for units in just about all scientific and International Trade matters. No more Furlongs per Fortnight or Stones per Hectare in science (those are part of ye olde English system).

NOTE: There are links to many other websites with interesting units and information on various unit systems and unit conversion calculators and some downloadable conversion programs in other pages here, for example:- Unit Conversions Pages.

*In Scales of Measurement on HyperStat describes the four categories or scales of measurement:

  1. nominal (or categorical),
  2. ordinal,
  3. interval, and
  4. ratio.

It then briefly summarizes several aspects of scales of measurement including: (a) the measurement principle involved for each scale, (b) examples of the measurement scales, (c) permissible arithmetic operations for each scale, and (d) examples of statistics that are appropriate for each scale.

*NIST Technical Note No. 1297 on The Expression of Uncertainty in Calibration Accuracy vs.inaccuracy; measurement necessarily involves errors and inaccuracy.The usage of these terms is perhaps best described in this electronic copy from The National Institute of Science and Technology (NIST). NB:-It is a very slight revamp of ISO’s Guide to Uncertainty in Measurement or GUM.

One truism is: every measurement has an error. The hard part in measuring usually is learning the size of the error with a certain amount of confidence.

An old friend used to say, “When you begin to prove that the error is larger than your expectations, you’re probably doing it correctly”.

It’s not always an easy job to learn the size of a measurement error, but seldom impossible; it takes a logical approach, nit-pickin’ persistence and some imagination.

The terminology used in measurement can be very specialized, so much, in fact, that a special vocabulary was published to help minimize errors in understanding specific terms. It is known as the Guide to the Expression of Uncertainty in Measurement (GUM). A free copy is online in several places, one of which is on the NIST website at: https://www.nist.gov/publications/terminological-aspects-guide-expression-uncertainty-measurement-gum.

* Measurement Theory FAQ A brief look at key concepts and references in the detailed world of measurement theory, courtesy of Warren S. Sarles’ 1996 web page from The SAS Institute (now known as SAS)

*“Metrology and Measurement”, a Keysight web resource, can also help one understand measurements. It provide links to many other sources of information. It introduces the world of measurement mostly from the perspective of test and electrical measurements, but the concepts remain the same regardless of the variables being measured.

This link will provide some insight into what is meant by measurement as well as the world-wide group of specialists and organizations with metrologists (Note: not meteorologists-remember, they forecast weather)

* MEASUREMENT SCIENCE CONFERENCE An annual scientific and engineering meeting of those involved in measurements.

Visit https://mrpyrometer.com/static-pages/ to see all the related measurement pages and more.

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