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How Does a Depth Indicators Work?

Depth indicators (dial indicators) are frequently used to measure surface discontinuity depths. Examples of discontinuities are pits, corrosion, or wastage. Verification of dimensions can also be conducted. In either case, zero depth must first be verified. The dial indicator or the digital read-out indicator is placed on a flat surface and zeroed. It is then moved over the depression. The spindle movement indicates the depth of the depression. When using the older dial indicator, the sweep hand rotations must be counted if the movement exceeds one 360?sweep. If a digital indicator is used, one must note the minimum and maximum point to which the indicator or its extensions are to range i. e.,0 ’? to 1’’or 4’?to 5’? etc. it is a common mistake not to count the number of rotations or not to note the beginning and end range of the indicator, resulting in only the last increment of measurement being accurate.