In metrology, the sensitivity of a measuring instrument is that metrological characteristic that provides information on the instrument’s ability to detect small variations in the input quantity; in other words: the increment of the output signal (or response) to the increment of the input measured signal. It can be defined also as the ratio of the incremental output and the incremental input. While defining the sensitivity, we assume that the input-output characteristic of the instrument is approximately linear in that range. It also represents a static characteristic of an instrument.
Again sensitivity of an instrument may also vary with temperature or other external factors. This is known as sensitivity drift. In order to avoid such sensitivity drift, sophisticated instruments are either kept at a controlled temperature, or suitable in-built temperature compensation schemes are provided inside the instrument.