1. . 
A device for measuring the diameter of the internal wall of a casing or tubing using multiple arms. By using a large number of arms, or fingers, the caliper can detect small changes in the wall of the pipe. The main purpose of the measurement is to detect deformations, the buildup of scale or metal loss due to corrosion. Typical multifinger calipers have between about 20 and 80 fingers, the larger numbers being necessary in larger pipes.