Dimensional metrology is the science of using physical measurement equipment to quantify the physical size, form, characteristics, and relational distance from any given feature.

History of metrology

Standardized measurements are essential to technological advancement, and early measurement tools have been found dating back to the dawn of human civilization. Early Mesopotamian and Egyptian

metrologist Metrology is the scientific study of measurement. It establishes a common understanding of units, crucial in linking human activities. Modern metrology has its roots in the French Revolution's political motivation to standardise units in Fran ...

s created a set of measurement standards based on body parts known as

anthropic units The term anthropic unit (from Greek '' άνθρωπος'' meaning human) is used with different meanings in archaeology, in measurement and in social studies. In archaeology In archaeology, ''anthropic units'' are strata, or deposits of materi ...

. These ancient systems of measurements utilized fingers, palms, hands, feet, and paces as intervals. Carpenters and surveyors were some of the first dimensional inspectors, and many specialized units craftsmen, such as the remen, were worked into a system of unit fractions that allowed for calculations utilizing analytic geometry. Later agricultural measures such as feet, yards, paces,

Cubit The cubit is an ancient unit of length based on the distance from the elbow to the tip of the middle finger. It was primarily associated with the Sumerians, Egyptians, and Israelites. The term ''cubit'' is found in the Bible regarding ...

fathoms A fathom is a unit of length in the imperial and the U.S. customary systems equal to , used especially for measuring the depth of water. The fathom is neither an International Standard (SI) unit, nor an internationally-accepted non-SI unit. Hi ...

, rods, cords, perch, stadia, miles and degrees of the Earth's circumference, many of which are still in use.

Early Measurement Tools & Standardization

Early Egyptian

rulers A ruler, sometimes called a rule, line gauge, or scale, is a device used in geometry and technical drawing, as well as the engineering and construction industries, to measure distances or draw straight lines. Variants Rulers have long ...

were incremented in units of fingers, palms, and feet based on standardized inscription grids. These grids outlined the standards of measurement as canons of proportion, and were made commensurate with Mesopotamian standards based on fingers, hands, and feet. In this system, four palms or three hands measured one foot; ten hands equaled one meter. These standards were used to measure and define property and regulated by law for several purposes, such as taxation, infrastructure, and more. such as buildings and fields were adopted by the Greeks, Romans, and Persians as legal standards and became the basis of European standards of measure. They were also used to relate length to area with units such as the khet, setat and aroura, area to volume with units such as the artaba and space to time with units such as the Egyptian minute of march, the itrw which recorded an hours travel on a river, and the days sail.

Modern tools

Modern measurement equipment include hand tools, CMMs (

coordinate-measuring machine A coordinate measuring machine (CMM) is a device that measures the geometry of physical objects by sensing discrete points on the surface of the object with a probe. Various types of probes are used in CMMs, the most common being mechanical and l ...

s), machine vision systems, laser trackers, and optical comparators. A CMM is based on

CNC Numerical control (also computer numerical control, and commonly called CNC) is the automated control of machining tools (such as drills, lathes, mills, grinders, routers and 3D printers) by means of a computer. A CNC machine processes a p ...

technology to automate measurement of Cartesian coordinates using a touch probe, contact scanning probe, or non-contact sensor. Optical comparators are used when physically touching the part is undesirable; components that consist of fragile or mailable materials require measurement using non-contact techniques. Instruments can now build 3D models of a part and its internal features using CT Scanning or X-Ray imaging.

Relative measurements

Measurements are often expressed as a size relative to a theoretically perfect part that has its geometry defined in a print or computer model. A print is a

blueprint A blueprint is a reproduction of a technical drawing or engineering drawing using a contact print process on light-sensitive sheets. Introduced by Sir John Herschel in 1842, the process allowed rapid and accurate production of an unlimited number ...

illustrating the defined geometry of a part and its features. Each feature can have a size, a distance from other features, and an allowed tolerance set on each element. The international language used to describe physical parts is called Geometric Dimensioning & Tolerancing (colloquially known as GD&T). Prints can be hand drawn or automatically generated by a computer

CAD model Computer-aided design (CAD) is the use of computers (or ) to aid in the creation, modification, analysis, or optimization of a design. This software is used to increase the productivity of the designer, improve the quality of design, improve co ...

. However, computer controlled measurement like coordinate measuring machines (CMMs) and vision measuring machines (VMMs) can measure a part relative to a CAD model without the need for a print. Typically, this process is done to reverse engineer components.

Mechanical engineering

Industrial metrology is common in manufacturing quality control systems to help identify errors in component production and ensure proper performance. Blueprints and 3D CAD models (as described above) are usually made by a

mechanical engineer Mechanical may refer to: Machine * Machine (mechanical), a system of mechanisms that shape the actuator input to achieve a specific application of output forces and movement * Mechanical calculator, a device used to perform the basic operations of ...

References

External links

National Institute for Standards and Technology Dimensional Metrology Portal

An example of Industrial Metrology equipment.

The Dimensional Metrology Standards Consortium is an ANSI standards organization that identify needed standards in the field of digital metrology
Metrology Dimension Manufacturing