Vernier caliper reading practice

Read main and vernier scales, correct signed zero errors and find resolution.

Practise

Resolution

20 vernier divisions span 19 mm of the main scale. Find the resolution in mm.

Main divisions are 1 mm; 20 vernier divisions span 19 mm. Read the aligned index from 0 to 19. At index 0, the final endpoint also aligns. This is a scale close-up.

Read the main scale above and the vernier below. Scroll the fine scale sideways on a small screen.

Diagram text alternative

Main-scale mark immediately left of vernier zero: 43 mm. Aligned vernier division: 1. 20 vernier divisions span 19 mm.

Larger diagram

Hint

Take the main-scale mark immediately left of vernier zero. Add the aligned vernier division multiplied by the resolution.

Worked solution

Resolution = 1 mm − 19/20 mm = 0.05 mm.

Another question

Question type: Mixed practice

Report a problem

Read the main scale and vernier scale

For a vernier with resolution 0.1 mm, suppose the main-scale reading just left of the vernier zero is 24 mm and the sixth vernier line aligns. Reading = 24 + 6 × 0.1 = 24.6 mm. Use the instrument’s stated resolution; different verniers have different increments.

The main-scale reading is the last mark before the vernier zero. The aligning line contributes a fraction of a main-scale division, not six extra millimetres. Apply a zero-error correction only when one is supplied or established.

Compare with a micrometer reading

Read the main scale first

Use the main-scale mark immediately to the left of vernier zero. Add the number of the aligned vernier mark multiplied by the resolution. The main scale here has 1 mm divisions. Use an aligned index from 0 through N − 1. When index 0 aligns, the final endpoint N also aligns; that endpoint repeats the zero position.

Find the resolution

If N vernier divisions span N − 1 mm, each vernier division is (N − 1)/N mm. The difference from a 1 mm main division is 1/N mm: 0.1 mm for N = 10 or 0.05 mm for N = 20.

Correct the zero

Corrected length = indicated length − signed zero error. Subtract a positive error; add the magnitude of a negative one. The zero error is supplied as the indication when the jaws close. Scale marks align exactly in these exercises.

A-level relevance

AQA 7408: 7.1 AT e (selected); OCR A H556: 1.2.2(e) (selected). Tasks cover the selected skills listed above.

AQA specification · OCR A specification · AQA practical handbook · OCR practical skills handbook