Chapter 1: STANDARDS OF MEASUREMENT
Definition of Metrology: Metrology (from Ancient Greek metron (measure) and logos
(study of)) is the science of measurement. Metrology includes all theoretical and practical
aspects of measurement.
Metrology is concerned with the establishment, reproduction, conservation and transfer
of units of measurement & their standards.
For engineering purposes, metrology is restricted to measurements of length and angle &
quantities which are expressed in linear or angular terms.
Measurement is a process of comparing quantitatively an unknown magnitude with a
Objectives of Metrology: The basic objectives of metrology are;
1. To provide accuracy at minimum cost.
2. Thorough evaluation of newly developed products, and to ensure that components
are within the specified dimensions.
3. To determine the process capabilities.
4. To assess the measuring instrument capabilities and ensure that they are adequate for
their specific measurements.
5. To reduce the cost of inspection & rejections and rework.
6. To standardize measuring methods.
7. To maintain the accuracy of measurements through periodical calibration of the
8. To prepare designs for gauges and special inspection fixtures.
Definition of Standards:
A standard is defined as “something that is set up and established by an authority as rule
of the measure of quantity, weight, extent, value or quality”.
For example, a meter is a standard established by an international organization for
measurement of length. Industry, commerce, international trade in modern civilization
would be impossible without a good system of standards.
Role of Standards: The role of standards is to achieve uniform, consistent and repeatable
measurements throughout the world. Today our entire industrial economy is based on
the interchangeability of parts the method of manufacture. To achieve this, a measuring
system adequate to define the features to the accuracy required & the standards of
sufficient accuracy to support the measuring system are necessary.