Bevel Protractor

To measure internal and external angle of given object with the help of bevel protractor

1. Lab session # 5: To measure internal and external angle of given object with the help of Bevel Protractor

2. BEVEL PROTECTOR: The angles can be measured by precision instrument that is known as universal bevel protractor. The Vernier scale is attached on base of this protractor. Base circular section contains a protractor dial that shows divisions in degrees. Dial also possesses the fitted sliding blade that has the capability of extending in any direction. The dial and blade rotate together. A small pinion provides fine adjustments and this pinion makes contact with the blade gear. Adjustment knob TURRET

3. Least Count On every side of zero line, the dividing of Vernier scale is done into the 12 divisions. The space of one Vernier division is five minute. If Vernier scale zero matches with main scale line then the reading that we will achieve will be in degrees only. If line of other than zero of Vernier scale matches with main scale line then five will be multiplied with the divisions number on Vernier scale that are beyond zero and the number which will obtain will be further added into indicated full degrees number on the protractor dial . Least Count = 1 degree / 12 div = 60 minutes / 12 div = 5minutes

4. WORKING

5. How to Read a Bevel Protector? On swivel plate, the line position provides the reading directly with respect to divisions on dial for angle measurements equal to ninety degrees or less than ninety degrees but for angle measurement of greater than ninety degrees then the degrees number that is shown on the dial will be subtracted from 180 degrees.   Check the line of other than zero of Vernier scale that matches with main scale line then five will be multiplied with the divisions number on Vernier scale that are beyond zero and the number which will obtain will be further added into indicated full degrees number on the protractor dial. Clockwise Vernier scale Anti-clockwise Vernier scale

6. PROCEDURE Firstly, the object is grasped in between the bevel protractors sliding and fixed blade. On swivel plate, the line position provides the reading directly with respect to divisions on dial for angle measurements equal to ninety degrees or less than ninety degrees but for angle measurement of greater than ninety degrees than the degrees number that is shown on the dial will be subtracted from one eighty degrees. Then check the line of other than zero of Vernier scale that matches with main scale line then five will be multiplied with the divisions number on Vernier scale that are beyond zero and the number which will obtain will be further added into indicated full degrees number on the protractor dial.

7. PROCEDURE

8. TABLE

9. POSSIBLE ERRORS Angle cannot be measured in decimal points.   The error can happen due to damaged instrument Parallax error, personal or instrumental error.   Error might occur because of scratches on magnifying glass.   Observer carelessness can also be the cause of error.

10. THANK YOU