chapter  4
18 Pages

Uncertainties in Physical Measurements

Making measurements of physical quantities, such as temperature, flow rate, and pollutant concentration, is so commonplace an activity in occupational exposure assessment that we seldom think about the complexity of the process. A simple definition of


is “that it is the process of assigning specific numerical value to a particular characteristic of the physical world.” A measurement system is a tool used for this quantification of the physical variable. The two main measurement tasks are (1) to construct a suitable “ruler” or reference scale and then (2) to compare the unknown quantity being measured with the divisions on the scale. Thus, we can describe a rectangular table by measuring its width and length using a tape measure and stating that the table is 2 m wide and 4 m long, and has an area of 8 m