Dial indicators — also known as dial gages, clocks, comparators or just indicators — are widely used as basic gages for measuring linear dimensions. Dial indicators have been around since the early 1900s. While digital indicators may be gathering more attention recently, dial indicators are unlikely to disappear any time soon. Dial indicators provide good value for their resolution. Experienced users like them because the analog dial gives a sense of direction and scale. With a glance, one can quickly determine if the part is larger or smaller than the master setting and by a degree of how much. Almost no thinking is involved. With the added capability of tolerance hands, the user can simply check if the indicator’s needle is within the tolerance bands and then move on to the next part.
Many dial indicators have a very short measuring range and thus are more apt to be used as a comparative device — comparing the part to a known master. However, dial indicators with a long range can cross over to become a measuring instrument and directly read the size of the part over the reference surface.