In vernier caliper readings, what does aligning the vernier scale with the main scale indicate?

• A. The zero on the vernier aligns with main scale mark indicating precise reading
• B. The measurement is invalid
• C. The instrument is out of calibration
• D. The main scale is not read

Answer: (A)

Vernier calipers combine a main scale with a sliding vernier scale to give a precise reading. The zero line on the vernier sets the baseline on the main scale; when that zero sits on a main-scale mark, it means the fractional portion is zero and the reading is simply the value indicated by that main-scale mark. The vernier then serves to confirm any tiny offset, but if the zero aligns exactly, there is no extra fraction to add. This is a normal, precise reading, not an indication of invalid measurement or calibration problems, and it shows that you’re reading from the correct baseline on the main scale.