In Fig. 13, the light falls on two gaps of 2.0 mm and 2.2 mm. There is a variation of 0.2 mm in gap sizes of its self-weight due to vertical standing. For measurements the vertical light is moved horizontally in a length of 45 mm. The complete horizontal length of the copper strip is 70 mm. The measurements are obtained with a maximum deviation of 70 µm with an accuracy of 3 µm. The maximum error in reading 2.2 mm gap is around 3.2% and the error is 3.5% for the 2.0 mm gap. The measurements from the light falling on the solid copper strip are shown in Fig. 14. The measurements are repeated with RPMs of 5000 and 8000. The spot size measurements show a spot size variation at different RPMs (Fig. 6). This introduces measurement difference at the two RPMs. The measurements are done with a maximum error of 13% from the original size.