Measurement: System, Uncertainty and Response

Abstract

A measuring instrument transforms a measurand, i.e., a physical variable to be measured, to provide comprehensible output. An instrument can be aptly analysed and synthesized as a system which is a set of interconnected components functioning as a unit, while response is a measure of such unit’s fidelity to its purpose. A real instrument’s response is neither perfect nor identical even under static and replicate-conditions. So appropriate approach to quantify the deviation from the true value is required. It is now widely recognized that measurement results should be expressed in terms of estimated value and an associated uncertainty value obtained by proper analysis. System response analysis is further complicated in dynamic measurements as an instrument does not respond instantaneously to an input that varies in time. This obviously creates a measurement problem, and if these effects are not accounted for, dynamic errors are introduced. Therefore, the performance of a measuring instrument is to be specified in terms of both static and dynamic performance parameters.