Micrometer is used for more accurate measurements of the small lengths. e.g measuring the diameter of a wire or thickness of a small plate.
A micrometer screw gauge consists of a fine screw of usually 1 ot 0.5 mm pitch, which moves when rotated through a nut as shown in the fig.
There are two scales, the linear millimeter scale is parallel to the axis of the screw and the circular scale at the end of the screw is divided in to 100 or 50 equal parts, so that when the screw is turned through one division, it moves through 100th or 50th part of its pitch as the case may be.
To use the micrometer we have to know the following things.
Pitch of the micrometer screwgauge
Least count of the micrometer screwgauge
How to make the data table to record the values