# Range of interval (or span)

In metrology, the range of the interval $$[a, b]$$ is the difference $$(b-a)$$ and is denoted by $$r[a, b]$$. It also represents a static characteristic of an instrument. It defines the maximum and minimum values of the inputs or the outputs for which the instrument is recommended to use. For example, for a temperature measuring instrument the input range may be 100÷500 °C and the output range may be 4÷20 mA.