One of the qualities of measuring instruments is their sensitivity. A measuring instrument is more sensitive the smaller the quantity that it is able to measure.
The sensitivity with which measuring instruments are made depends on what they will be used for. It makes no sense to produce some scales which measure mg for a baker to use.
The sensitivity of a measuring instrument indicates how many figures of a measurement are significant. Find out how many figures can be known as a result of a measurement taken in the following visual.