Indicator (distance amplifying instrument)
In various contexts of science, technology, and manufacturing, an
indicator is any of various instruments used to accurately measure small distances and angles, and amplify them to make them more obvious. The name comes from the concept of
indicating to the user that which their naked eye cannot discern; such as the presence, or exact quantity, of some small distance. Many indicators have a dial display, in which a needle points to graduations in a circular array around the dial. Such indicators, of which there are several types, therefore are often called
dial indicators. Non-dial types of indicators include mechanical devices with cantilevered pointers and electronic devices with digital displays. Indicators may be used to check the variation in tolerance during the inspection process of a machined part, measure the deflection of a beam or ring under laboratory conditions, as well as many other situations where a small measurement needs to be registered or indicated. Dial indicators typically measure ranges from 0.25mm to 300mm, with graduations of 0.001mm to 0.01mm or 0.00005in to 0.001in.