Therefore, every graduation on the main scale is equal to 0.025 in. or one-fortieth of an inch. The sliding scale is marked from zero to 25. Some readers may think that the eighteenth graduation is more in-line than the nineteenth. Subjectivity such as this makes vernier calipers difficult to use for less skilled workers. Also, if your eyes aren't centered over the vernier scale, parallax errors can occur when the two scales of the vernier are on different planes.
Dial calipers require less skill to use and are easier to read.
Their higher cost is offset by fewer reading errors and higher throughput. Unlike vernier calipers that can measure in inches and the metric system, most dial calipers can only measure in one. An electronic caliper is easier and faster to read than a vernier or dial caliper, but other advantages may be less apparent. Electronic calipers usually provide better resolution, 0.0005 in. This feature is indispensable when comparing two components.