A caliper is a precision measuring instrument used to dimension an object with high accuracy. These can be found in a variety of lengths, imperial or metric, and either with a vernier scale, dial, or in digital forms. For this article, I will be using a dial caliper as an example. A caliper can take four types of measurements which includes the outside jaws, inside jaws, depth probe, and step measurement. Each type of caliper will have their own advantages and disadvantages. A vernier caliper is the most basic type of caliper, it does take the longer and require more skill to read, but has minimal moving parts and there is no need for battery maintenance. A caliper equipped with a dial indicator, on the other hand, is easier to read, there is no battery maintenance, but has more moving parts. A digital caliper does have electronics which require battery upkeep but is by far the easiest to read...
A micrometer is a precision measuring tool that uses linear movement in order to measure the thickness, diameter, and length of an object. For this explanation, I will be using the outside style micrometer which features a "C" frame. Other types also include an inside and depth variations which do not include the "C" frame. They are available in both imperial and metric measuring systems and can also be found in vernier, mechanical digital, electronic digital, and dial measurement outputs. Below you will see photos of both the vernier and mechanical digital styles. Qualities of micrometers will vary between manufacturers, along with the accuracy as well...