Vernier Fowler Calipers
A variation to the more traditional caliper is the inclusion of a vernier scale; this makes it possible to directly obtain a more precise measurement. Vernier calipers can measure internal dimensions, external dimensions using the lower jaws and depending on the manufacturer, depth measurements by the use of a probe that is attached to the movable head and slides along the centre of the body. This probe is slender and can get into deep grooves that may prove difficult for other measuring tools. The vernier scales may include both metric and inch measurements on the upper and lower part of the scale. Vernier calipers commonly used in industry provide a precision to a hundredth of a millimeter (10 micrometers) or one thousandth of an inch. A more precise instrument used for the same purpose is the micrometer.