Measuring Instrument And Selection

MEASURING INSTRUMENT AND THEIR SELECTION

A measuring instrument is any device that may be used to obtain a dimensional or angular
measurement. The important characteristics which govern the selection of instruments are measuring range, accuracy and precision.
Some instruments, such as a steel rule, may be used to read directly; others like caliper, are used for
transforming or comparing dimensions.
Transformation of a measurable quantity into the required information is a function of measuring
instruments.
Generally, measuring instruments are classified as follows:

i. On the basis of function

a. Length-measuring instruments
b. Angle measuring instruments
c. Surface-roughness measuring instruments
d. Geometrical-form-checking instruments

ii. On the basis of accuracy

a. Most accurate instruments
b. Moderate accurate instruments
c. Below moderate accurate instruments

iii. On the basis of precision

a. Precision measuring instruments
b. Non-precision measuring instruments