pinned: true | type: | topic: instruments
Apparatus Reference (Wikimedia Commons):
https://commons.wikimedia.org/wiki/Special:FilePath/$Vernier_{caliper}$.svg?width=600
Cue Column | Note-Taking Column
| Cue | Notes |
|---|---|
| What is LC? | LC (Least Count) = smallest measurable value. For Vernier: LC = 1 MSD − 1 VSD. |
| Vernier LC formula | 50 VSD = 49 MSD, 1 MSD = 1 mm → LC = 1 − 49/50 = 0.02 mm |
| Reading = ? | MSR + (coinciding VSD × LC) |
| Positive zero error | Vernier zero to the RIGHT of main scale zero → instrument reads MORE → SUBTRACT |
| Negative zero error | Vernier zero to the LEFT → reads LESS → ADD |
| Screw gauge LC | LC = pitch / no. of circular divisions = 0.5 mm / 50 = 0.01 mm |
| Screw gauge reading | MSR + (CSR × LC) |
| Backlash error | Caused by reversing direction. Fix: always rotate ONE way only. |
| What Vernier measures | External diameter, internal diameter, depth |
| What screw gauge measures | Thickness of thin sheets, wire diameter |
| Dimensional formula | Both: [L], SI unit: m |
Summary (Bottom)
The Vernier caliper and screw gauge are precision instruments. Vernier: LC = 0.02 mm (50 div), reading = MSR + n×LC. Screw gauge: LC = 0.01 mm, backlash error avoided by unidirectional rotation. Zero error: positive → subtract; negative → add (mnemonic: PS-NA).