Screw Gauge Total Reading — the NEET Physics formula with its derivation, variables, validity constraints and worked solver.
Screw Gauge Total Reading Essential for measuring small dimensions with high precision (typically 0.01 mm or 0.001 cm), such as wire diameter or sheet thickness. Define Pitch: Distance moved by the screw for one complete rotation. Calculate Least Count (LC): Pitch / Number of divisions on circular scale. Observe Main Scale Reading (MSR): The last visible line on the sleeve. Observe Circular Scale Coincidence (CSC): The division matching the baseline. Sum the components: TR = MSR + (CSC LC). The instrument must not have backlash error (or it must be avoided by rotating in one direction). Zero error (if any) must be subtracted from the Total Reading to get the True Reading. Adding the circular scale division number (CSC) directly to MSR without multiplying by the Least Count. Ignoring Zero Error (positive or negative) which leads to systematic error. Confusing Pitch (distance per rotation) with Least Count (measurement resolution).