DESIGN PROCESS/APPROACH

The Vernier caliper is an instrument that allows you measure lengths much more accurate
than the metric ruler.  The smallest increment in the vernier caliper you will be using is
(1/50)mm = 0.02mm = 0.002cm.  Thus, the uncertainty is ∆x = (1/2)0.002 cm = 0.001 cm.
The vernier scale consists of a fixed metric scale and a sliding vernier scale. The fixed scale
is divided into centimeters and millimeters, while the vernier scale is divided so that 50
divisions on it cover the same interval as 49 divisions on the main scale.  Thus, the length
of each scale vernier division is 49/50 the length of a main scale division.  Close the jaws
completely and note that the first line at the far left on the vernier scale (called the “zero”
or “index” line) coincides with the zero line on the main scale.  Carefully compare and see
that the first vernier division is 0.02 mm short of the first main scale division, the second
vernier division is 0.04 mm away from the second main scale division, and so on.  If the
jaws are slightly opened it is easy to tell what fraction of the main scale division the vernier
index has moved by noting which vernier division best coincides with a main scale
division.
A measurement is made with a vernier caliper by closing the jaws on the object to be
measured and then reading the position where the zero line on the vernier falls on the main
scale.  The measurement is incomplete until an additional fraction of a main scale division
is determined.  This is obtained by noting which line on the vernier scale (0,2,4,6,8)
coincides best with a line on the main scale.