#ELECTRONIC PROTRACTOR MANUAL#
Manual (1), and Mitscherlich's optical (2) goniometers for use in crystallography, c. The readings can be taken either to the right or to the left, according to the direction in which the zero on the main scale is moved. Since the spaces, both on the main scale and the Vernier scale, are numbered both to the right and to the left from zero, any angle can be measured. To measure an angle of over 90°, subtract the number of degrees as indicated on the dial from 180°, as the dial is graduated from opposite zero marks to 90° each way.
To measure an angle between the beam and the blade of 90° or less, the reading may be obtained direct from the graduation number on the dial indicated by the mark on the swivel plate. When the edges of the beam and blade are parallel, a small mark on the swivel plate coincides with the zero line on the graduated dial. The bevel protractor consists of a beam, a graduated dial and a blade which is connected to a swivel plate (with Vernier scale) by thumb nut and clamp. It reads to 5 arcminutes (5′ or 1 / 12°) and can measure angles from 0° to 360°. The bevel protractor is used to establish and test angles to very close tolerances. Universal bevel protractors are also used by toolmakers as they measure angles by mechanical contact they are classed as mechanical protractors.
It has wide application in architectural and mechanical drawing, although its use is decreasing with the availability of modern drawing software or CAD. Sometimes Vernier scales are attached to give more precise readings. A bevel protractor is a graduated circular protractor with one pivoted arm used for measuring or marking off angles.
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