Manufacturing Technology: Theory and Problems, Second Edition

CHAPTER 14

Metrology

• Metrology is the science of measurement.
• SI (International Standard) unit is universally accepted. It is also called metric units of standard. There are seven basic and two supplementary SI units. They are shown in Tables 14.1 and 14.2, respectively.

   

  Table 14.1 Basic units

  Quantity	Unit	Symbol
  Length	Metre	m
  Mass	Kilogram	kg
  Time	Second	s
  Electric current	Ampere	A
  Temperature	Kelvin	K
  Luminous Intensity	Candela	cd
  Amount of substance	Mole	mol

   

  Table 14.2 Supplementary units

  Quantity	Unit	Symbol
  Plane angle	Radian	rad
  Solid angle	Steradian	sr

• The important characteristics of a measuring instrument are: accuracy, sensitivity and repeatability.
• There are six degrees of freedom: three linear ...