Reading a Vernier scale

Vernier: a moveable graduated scale. Two scales are used with slightly different pitches. The fixed, non-moveable scale is accurate and true to scale. The second scale, the moveable scale is graduated with the number number of increments needed to complete the stationary scale to it's level of accuracy.
With the invention of digital readouts, vernier scales are not used that often. We no longer use slide rules with the invention of the calculator and many of the old tools used as measuring equipment now have a digital scale and readout.
In the machining industry their is a limit to the length that can be purchased with a digital output.
Digital outputs are also less resilient than their vernier counterparts. Digital equipment gets dropped, spilled on, glass scratched, accidents just happen. Vernier calipers can be purchased in very long lengths. With only one moving part, It retains it's accuracy over a much longer time period and normal abuse. Only the temperature changes need be accounted for on lengthy measurements.





Reading the scale:
It is important to note, the graduations between the numbers on the stationary scale. The largest set of numbers is the inch graduations. Then between the inches there are 1-9. This means that the distance between number 6 and 7 is .1 inch. Notice that in between 6 and 7 there are 4 graduations. So, .1 divided by 4 is .025. There are 25 graduations on the moveable scale. Because a different set of graduations may be on a set of calipers from another manufacturer. For example, If there were only one graduation in between number 6 and 7, then the formula says that each line is .05 inch. .1 divided by 2. Therefore the moveable scale must have 50 increments instead of 25.

The scale above reads: A + B + C + D
A = 0
B = .5
C = .025  ( the 0 line is just past the first increment but, not to the second )
D = .008  ( the number 8 on the moveable scale lines up- the best )

Measurement is 0.532 inches