Indicator (distance amplifying instrument)

In various contexts of <a href="/facts/Science/IJoaD7rs">science</a>, <a href="/facts/Technology/9Uav5WVR">technology</a>, and manufacturing (such as <a href="/facts/Machining/Yrjfj6IV">machining</a>, <a href="/facts/Metal_fabrication/7WLsJYXB">fabricating</a>, and <a href="/facts/Additive_manufacturing/lbvWU3t0">additive manufacturing</a>), an indicator is any of various instruments used to accurately measure small distances and <a href="/facts/Angle/gFUTEQYq">angles</a>, 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 (for example, a small height difference between two flat surfaces, a slight lack of <a href="/facts/Concentric/xR1I5N8y">concentricity</a> between two cylinders, or other small physical deviations).
The classic mechanical version, called a dial indicator, provides a <a href="/facts/Dial_(measurement)/nyX6TVjJ">dial</a> display similar to a clock face with clock hands; the hands point to graduations in circular scales on the dial which represent the distance of the probe tip from a zero setting. The internal works of a mechanical dial indicator are similar to the precision clockworks of a mechanical wristwatch, employing a <a href="/facts/Rack_and_pinion/rA4eyqkf">rack and pinion</a> gear to read the probe position, instead of a pendulum <a href="/facts/Escapement/8AgmCy7C">escapement</a> to read time. The side of the indicator probe shaft is cut with teeth to provide the rack gear. When the probe moves, the rack gear drives a pinion gear to rotate, spinning the indicator "clock" hand. Springs preload the gear mechanism to minimize the backlash error in the reading. Precise quality of the gear forms and bearing freedom determines the repeatable precision of measurement achieved. Since the mechanisms are necessarily delicate, rugged framework construction is required to perform reliably in harsh applications such as <a href="/facts/Machine_tool/XPHaqz0p">machine tool</a> metalworking operations, similar to how wristwatches are ruggedized.
Other types of indicator include mechanical devices with <a href="/facts/Cantilever/Ueu6vIXI">cantilevered</a> pointers and electronic devices with digital displays. Electronic versions employ an <a href="/facts/Linear_encoder/yslJ6jeE">optical</a> or <a href="/facts/Capacitive_sensing/KqI9zuD4">capacitive</a> grating to detect microscopic steps in the position of the probe.
Indicators may be used to check the variation in <a href="/facts/Tolerance_(engineering)/zRrj34dF">tolerance</a> during the inspection process of a machined part, measure the <a href="/facts/Deflection_(engineering)/xroy2lX2">deflection</a> 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 0.25 mm to 300 mm (0.015in to 12.0in), with graduations of 0.001 mm to 0.01 mm (<a href="/facts/Metric_system/to24H0YK">metric</a>) or 0.00005<a href="/facts/Inch/CocFfm8p">in</a> to <a href="/facts/Thousandth_of_an_inch/6jJ6uVUn">0.001in</a> (<a href="/facts/Imperial_and_US_customary_measurement_systems/12BRjE19">imperial/customary</a>).
Various names are used for indicators of different types and purposes, including dial gauge, clock, probe indicator, pointer, test indicator, dial test indicator, drop indicator, plunger indicator, and others.

Indicator (distance amplifying instrument) open-in-new

Indicator (distance amplifying instrument)