Measurements and Instrumentation
The measurement of a given quantity is essentially an act or the result of comparison between the quantity (whose magnitude is unknown) & a predefined standard. Since two quantities are compared, the result is expressed in numerical values.
i) The standard used for comparison purposes must be accurately defined & should be commonly accepted
ii) The apparatus used & the method adopted must be provable.
It may be defined as a device for determining the value or magnitude of a quantity or variable.