Lakhasly

Analogue instruments produce outputs that change continuously with the measured quantity, offering an infinite range of values within their design limits. A classic example is the deflection-type pressure gauge (Figure 2.1), where the pointer moves smoothly with the input. While theoretically having infinite positions, the human eye can only distinguish a limited number, determined by scale size and division. In contrast, digital instruments generate outputs in discrete steps, allowing only a finite number of values.

An analogue instrument gives an output that varies continuously as the quantity being
measured changes. The output can have an infinite number of values within the range
that the instrument is designed to measure. The deflection-type of pressure gauge
described earlier in this chapter (Figure 2.1) is a good example of an analogue instru-
ment. As the input value changes, the pointer moves with a smooth continuous motion.
Whilst the pointer can therefore be in an infinite number of positions within its range
of movement, the number of different positions that the eye can discriminate between
is strictly limited, this discrimination being dependent upon how large the scale is and
how finely it is divided.
A digital instrument has an output that varies in discrete steps and so can only have
a finite number of values.