Metro-logy is defined as “the science of measurement,
embracing both experimental and theoretical determinations at any level of
uncertainty in any field of science and technology”. It establishes a
common understanding of units, crucial to human activity.
There are three types of Metrology:
- Scientific Metrology
- Applied, Technical or Industrial Metrology
- Legal Metrology
Scientific (fundamental) metrology
Scientific or fundamental metrology concerns the setting of
measurement standards and the establishment of units of measurement, unit
systems and quantity systems. Additionally, scientific metrology involves the
development of new methods of measuring as well as the transfer of tractability
from the standards to users.
Applied, technical or industrial metrology
Industrial metrology is the area of metrology science.
Applied, technical or industrial metrology involves the application of
measurement science to industrial processes including manufacturing. Additionally,
industrial metrology ensures the suitability and adequate functioning of
measurement instruments, their calibration and quality control of measurements.
Legal metrology
Defined by the International Organization of Legal Metrology
(OIML) as “the application of legal requirements to measurements and measuring
instruments”, legal metrology ensures the accuracy and reliability of
measurements where measured values can affect health, public safety, the
environment and the protection of consumers and fair trade.
THE HISTORY OF METROLOGY FROM GALILEO TO OPTICAL SYSTEMS
Metrology originates from antiquity. The first forms of
measurements were established to facilitate commerce and record human activity.
Time, weight and length were the first standards formulated. Over the course of history, dimensional metrology went
through several evolution.
Before 1789 (KING’S FOOT)
Scientists estimate that thousands of different measurement
units are used across Europe. Among them figure the pied duroi (the
king’s foot), which has a degree of pre-eminence. Nevertheless, many traders
have their own measuring tools, giving scope for frauds, extortions, and misrepresentations.
It is not until the establishment of the metric system that we started to see
harmonization in measurements.
The French Revolutionary government introduces the metric
system, now known as the International System of Units. One meter was
preliminary defined as one ten millionth of the distance between the North Pole
and the Equator crossing through Paris. Of course, the meter definition has
evolved over the centuries, but is still considered today as the length reference
to which every measuring tool refers.
1840 (PHOTOGRAMMETRY)
The first use of photogrammetry appears shortly after the emergence of
photography. The credit goes to French geodesist, François Arago. He presents
to the Academy of Science, a method using triangulation. This technology
enables him to determine the position of objects in space based on photographs
taken from different viewing angles, without knowing the position of the shots
beforehand.
1848 (SYSTEM PALMER)
French inventor J. Palmer receives a patent for the ‘System
Palmer’, the first micrometre still recognizable today with its
U-shaped frame. Modern micrometres closely follow the System Palmer’s basic
design of a U-shaped frame, thimble, sleeve, spindle, anvil, etc. Besides, all micrometres
and other hand tools must still be traceable to the International Standard.
American Physicist Albert A. Michelson thought detection of
motion through ether might be measurable. To do so, he invents a new instrument
called the interferometer. The results he obtains during his experiments
prove there is no earth motion relative to ether. This proof changes the
foundation of physics and leads to Albert Einstein’s theory of relativity in
1905.
1960 (CMM)
The Coordinate Measuring Machine first appears in
the early 60s and is made of 3D tracing devices with a simple digital readout
(DRO) displaying the XYZ position. The initial CMM was developed by the
Ferranti Company in Scotland during the 50s. This unit, however, had only two
axis. The very first three-axis prototypes arrive during the 1960s and are
invented by the Italian company DEA (now part of the Hexagon Metrology Group).
Soon afterwards, automated CMMs appear in the 60s to perform
complex inspections of Concorde supersonic jet engines. This invention leads to
the creation of the Renishaw Company in 1973, now the main supplier of CMM
measuring heads.
1980 (PORTABLE CMM)
Portable CMMs with measuring arms arrive in the
80s, revolutionizing the measurement process: it is now possible to bring metrology tools to the production floor. This
innovation eliminates the need to move manufactured parts to a dedicated,
controlled environment. However, because measuring arms use a classic
technology based solely on precision mechanical parts, these portable CMMs
remain very sensitive to vibrations and instabilities induced by the
environment. Therefore, considerable precautions are required when operating
them.
1985 (3D SCANNER)
Although the first 3D scanners were developed in
the 60s, it is not until 1985 that the laser technology is applied to 3D scanning. Prior, the 3D scanning models used lights,
cameras and projectors to perform a scan. However, a lot of time and effort was
required to scan objects accurately. Scanners built after 1985 use white light,
lasers and shadowing to capture a given surface.
1987 (LASER TRACKER)
The first laser tracker prototype is developed by
Dr. Kam Lau in 1986. One year later, Dr. Lau founds his company called
Automated Precision Inc. that will refine tracking technology, which leads to
building models with greater precision and portability. Laser trackers are
still the leading solution for measuring parts of large dimensions (e.g.
aircraft wings, auto frames, or large tooling). Nevertheless, for high volume
measurement, they compete against another technology: photogrammetry.
2000 (OPTICAL PORTABLE CMM)
Optical portable CMMs arrive in the metrology landscape
at the beginning of the millennium. They bring together the flexibility and
effectiveness of CMMs, the portability and simplicity of portable CMM, with an
extra—optical portable CMMs are insensitive to vibrations,
making them perfectly adapted to shop-floor measurements. The technology has
seen many improvements and developments during the past years, to the point
where they now compete with CMMs. They are now integrated into the inspection process and even manage to challenge the
metrology market.
As a CAD Designer science of measurement is the very core of
us, and this is very necessary to understand the concept of metrology. It is
used to design the conditions for observation of a phenomenon, to build and
qualify the instruments required for its observation and to determine whether
the results obtained are significant. Rock dating, characterisation of
gravitational fields, determination of certain chemical or physical constants
all involve measurement activities. Measurement enables our
industries to be innovating and competitive, Competitiveness involves quality,
which is the ability of a product to meet consumer and user requirements, and
which involves all types of measurement in order to study and satisfy customer
expectations. Quality can be demonstrated to customers through certification,
itself based on measurements.