A backlash error is an error in the observation
caused due to wear and tear of threads of the screw observed.
It is caused while reversing the direction of rotation
of the thimble where the tip of the screw does not start moving in the opposite direction at once,
but remains stationary for a part of rotation.
Avoid backlash error:
⋅ While taking measurements, screw should be rotated in one direction only.