A Vernier caliper is a measuring device used to measure internal and external diameters as well as the depth to an accuracy much greater than a normal ruler or tape measure. The Vernier scale was invented by French mathematician Pierre Vernier in 1631 and is one of the most important technological advances in accurate measurement. Vernier calipers are used widely in engineering, science, design and technology and are often found on the desk or in the pockets of professionals from industrial designers and construction engineers to laboratory based scientists.