STANDARD
A standard is an object, system, or experiment that bears a defined relationship to a unit of measurement of a physical quantity.
Standards are the fundamental reference for a system of weights and measures, against which all other measuring devices are compared
The ideal standard is independently reproducible without uncertainty
Any system of measurement must be related to a known standard otherwise the measurement has no meaning
BASIC CLASSIFICATION OF STANDARDS
PRIMARY STANDARDS:
It is prepared under the most careful of conditions and used in very rare intervals for comparison with secondary standards
SECONDARY STANDARDS:
Made as nearly as possible exactly similar to primary standards. Compared with primary standards at rated intervals
TERTIARY STANDARDS:
First standards to be used for reference purpose in workshops and laboratories. They are made as true copy of secondary standards
WORKING STANDARDS:
Made of low grade materials anr are most frequently used in workshops
In metrology one of the basic type of measurement is the measurement of the linear dimension
Linear dimension refers to the distance between two points on a straight line along any portion of a component or the object of inspection or measurement