Introduction to Measurement

This chapter provides an introduction to the various measurement techniques. The instrument choice is a compromise between performance characteristics, ruggedness and durability, maintenance requirements and purchase cost. Measurement techniques have been of immense importance ever since the start of human civilization, when measurements were first needed to regulate the transfer of goods in barter trade to ensure that exchanges were fair. The very first measurement units were those used in barter trade to quantify the amounts being exchanged, and to establish clear rules about the relative values of different commodities. Today, the techniques of measurement are of immense importance in most facets of human civilization. Measuring system exists to provide information about the physical value of some variable being measured. In simple cases, the system can consist of only a single unit that gives an output reading or signal according to the magnitude of the unknown variable applied to it. The starting point in choosing the most suitable instrument for the measurement of a particular quantity in a manufacturing plant or other system is the specification of the instrument characteristics required, especially parameters like the desired measurement accuracy, resolution, sensitivity, and dynamic performance. To carry out such an evaluation properly, the instrument engineer must have a wide knowledge of the range of instruments available for measuring particular physical quantities; and he/she must also have a deep understanding of how instrument characteristics are affected by particular measurement situations and operating conditions.