A vernier caliper is a measuring tool used in science for making extremely precise measurements. There is a pair of "jaws" that collapse around an object to be measured. The b
…oldface numbers on the fixed scale are in centimeters, and the tick marks between the boldface numbers are in millimeters. The left-most tick on the sliding part of the scale will allow you to read from the fixed scale the number of whole millimeters that the jaws are opened. The vernier caliper is used in length measurements to gain an additional digit or more of accuracy compared to a simple ruler. And more than just replacing rulers, they allow for accurate linear measurements (within the rated limits of the device) of distances that would be difficult or impossible to get with a hand held ruler. You can see from the image at the related link that vernier calipers typically have what look like one or two pairs of prongs. One pair could be adjusted to measure for example the outer diameter of tube-like objects or outer lengths of any number of different objects. You would open the prongs and carefully close them until they just touch the outer edges of such an object, giving a reading of the diameter or length. The other pair of prongs could be brought in tightly and then carefully expanded until they extend to a length of some inner space the dimensions of which you need to know. Vernier calipers are used, especially in metal engineering, to make very precise measurements of internal and external dimensions of small objects. The calipers slide together, and a reading is taken by visual examination of the sliding scales on the calipers. There are two scales, and careful scrutiny of the second scale enables greater precision than just using one scale. Although Vernier calipers have been used for many years, and have proven invaluable in ascertaining, within acceptable tolerances of accuracy, i.e. measurements down to fractions of a millimeter, the advert of digital technology makes it possible to measure dimensions to an even greater precision! The down-side of digital calipers, however, is that they need a battery, unless of course, you can get a solar powered one! For more information about Vernier and digital calipers, how they work, and photographs, see Related links below. (MORE) 
