Least Count: LC = Pitch / Number of circular scale divisions Typical: LC = 0.5 mm / 50 = 0.01 mm

Reading: Measurement = MSR + (CSR * LC) where MSR = main scale reading, CSR = circular scale reading (division coinciding with reference line)

Zero error:

• Positive: When jaws are closed, circular scale zero is below the reference line. The reading is too high — subtract the zero error.
• Negative: Circular scale zero is above the reference line. The reading is too low — add the magnitude of zero error.

Backlash error: Caused by wear in the screw threads. Always rotate the screw in one direction while measuring to avoid this.