A simple protractor is a basic device used for measuring angles with a least count of 1° or ½°. Bevel Protractor is an angular measuring instrument capable of measuring angles with a least count of 5’.
The protractor dial is graduated in degrees with every tenth degree numbered. The sliding blade is fitted into this dial I.e. it may be extended to either direction and set at an angle to the base.
This protractor dial may be locked in any position by means of the spacing in the vernier scale is made in such a way that least count of it corresponds to 1/12th of a degree, which is equal to 5’.
The least count is the difference between one vernier division and two main scale divisions, which is 1/12° or 5′.
Sometimes, confusion arises regarding the direction in which the vernier has to be read. To eliminate the confusion we follow a simple rule. Always read the Vernier from zero in the same direction that you read the dial scale.