In a vernier micrometer caliper, to what increment can the reading be made?

• A. 0.0001
• B. 0.001
• C. 0.01
• D. 0.1

Answer: (A)

A vernier micrometer gains precision by combining a main scale with a vernier scale, which subdivides a single main-scale division. The main scale typically gives readings to the nearest 0.001 inch, and the vernier adds the ability to interpolate an additional 0.0001 inch. This works because 10 divisions on the vernier equal 9 divisions on the main scale, so one vernier division is 0.9 of a main-scale division and the difference between them is 0.0001 inch. When a line on the vernier aligns with a line on the main scale, that alignment indicates an extra amount in increments of 0.0001 inch to add to the main-scale reading. Readings therefore can be made to 0.0001 inch. The larger values would only reflect coarser, non-vernier readings. For example, if the main scale reads 0.125 inches and the vernier alignment corresponds to the 6th vernier division, the total would be 0.1256 inches.