SPHEROMETER SINGLE Disc

The least count of a spherometer is the smallest measurement that can be made with the instrument. It is determined by the pitch of the screw and the number of divisions on the circular scale. The pitch of the screw is the distance that the screw moves when it is turned one complete revolution. The circular scale is a graduated disc that is attached to the screw. The number of divisions on the circular scale indicates how many times the screw must turn in order to advance by one pitch. The least count of the spherometer is calculated by dividing the pitch of the screw by the number of divisions on the circular scale. Least count = Pitch / Number of divisions on the circular scale Where: Pitch is the distance that the screw moves when it is turned one complete revolution. Number of divisions on the circular scale is the number of divisions on the graduated disc that is attached to the screw. For example, if a spherometer has a pitch of 0.01 mm and a circular scale with 100 divisions, then the least count of the spherometer is: Least count = 0.01 mm / 100 = 0.001 mm In other words, the smallest measurement that can be made with this spherometer is 0.001 mm