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 (for example, a small height difference between two flat surfaces, a slight lack of concentricity between two cylinders, or other small physical deviations).
The classic mechanical version, called a dial indicator, provides a dial 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.
Gauge
A dimensional gauge or simply gauge is a device used to make measurements or to display certain dimensional information. A wide variety of tools exist which serve such functions, ranging from simple pieces of material against which sizes can be measured to complex pieces of machinery. Dimensional properties include thickness, gap in space, diameter of materials.
All gauges can be divided into four main types, independent of their actual use.
- Analogue instrument meter with analogue display (“needles”). Until the later decades the most common basic type.
- Digital instrument meter with analogue display. A screen that shows an “analogue meter”, commonly used in modern aircraft cockpits, and some hospital equipment etc.
- Digital instrument meter with digital display. Only numbers are shown at a digital display.
- Analogue instrument meter with digital display. Only numbers are displayed, but through a mechanical or electro-mechanical display (today very rare but has existed for clocks, certain Doppler meters and informational screens at many stations and airports)
Perspective Research Centre 
You must be logged in to post a comment.