Dial indicators are precision measurement instruments used to measure the alignment of a machine's components or the general deviation of any object from an expected standard. They are named for their clocklike faces, which consist of numbers arranged in a circle which a dial points to. Several different types of dial indicators exist, differentiated by factors such as their size, connection method and the type of information featured on their face.
Balanced Reading Dial Indicators
Balanced reading dial indicators are so named for the way that information is arranged upon the dial's face. Figures are printed upon the face of this dial running in two directions, starting from a zero in the centre. Often, positive numbers are featured to the right of the zero and negative numbers to the left.
Continuous Dial Indicators
Continuously numbered dial indicators do not have the two sets of numbers featured on balanced reading dial indicators. The figures on this type of dial indicators run in one direction without stopping and without any type of a separation.
Reversed Balanced Dial Indicators
Reversed balanced dial indicators are named because they have the same basic positive and negative scales to each side of a zero, but the positive numbers are to the left and the negative are to the right.
Reversed Continuous Dial Indicators
Reversed continuous, or counter-clockwise, dial indicators are the same as continuous dial indicators except that the numbers run in the opposite direction.
Test Dial Indicators
Test dial indicators look a great deal like a watch, except with a needle to one side. They are completely adjustable and can be calibrated to measure any type of machinery for which they are needed.
Plunger Dial Indicators
Plunger dial indicators also have a clocklike face but are characterised by the plungers mounted on one of their sides. They come in both mechanical and electronic designs. One common use for plunger dial indicators is to measure the work of injection moulding machines. The mechanism which allows this type of dial indicator to work is a rack and pinion, which changes the linear thrust of the plunger into rotary motion for the dial.
Lever Dial Indicators
Lever type dial indicators are characterised by their lever and scroll mechanisms, which cause the stylus to move. This type of dial indicators are more compact and easier to use than plunger-type dial indicators and are therefore quite often used.
Dial indicators can also be differentiated by the way in which they connect to the machine they are measuring. The most common ways in which a dial indicator connects is with the use of a C-clamp or a swivel clamp. A swivel clamp can also be used in conjunction with a swivel post.