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Micrometer reading practice

Read the scales, correct zero errors and record a micrometer measurement.

Practise

Near a scale rollover

Read the micrometer in mm. Assume the micrometer has no zero error.

This micrometer advances 0.5 mm per turn and has 50 thimble divisions. Readings align with a division. The enlarged scale is schematic; use the scale marks, not the width of the drawing.

Last visible sleeve mark: 4.50 mm. Thimble division at the reference line: 0. Pitch 0.5 mm; 50 divisions per turn.2344505Sleeve / mmThimble
Scale close-up: whole millimetres above the sleeve reference line, half-millimetres below.
Scale text alternative

Last visible sleeve mark: 4.50 mm. Thimble division at the reference line: 0.

Larger micrometer
Last visible sleeve mark: 4.50 mm. Thimble division at the reference line: 0. Pitch 0.5 mm; 50 divisions per turn.2344505Sleeve / mmThimble

Use decimals or e notation, e.g. 4.2e-3. Enter the unit separately.

Hint

Read the last visible whole or half-millimetre sleeve mark. Add the thimble division aligned with the reference line × 0.01 mm.

Worked solution
  1. Sleeve: 4.50 mm.
  2. Thimble: 0 × 0.01 = 0.00 mm.
  3. Indicated reading = 4.50 mm.
  4. Answer: 4.50 mm.
Another question
Question type: Mixed practice
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How to read a micrometer

Suppose the sleeve shows 5 mm and the extra half-millimetre mark is visible. The thimble aligns at 23 divisions of 0.01 mm. Reading = 5.50 + 0.23 = 5.73 mm. If the stated zero error is +0.02 mm, corrected diameter = 5.73 − 0.02 = 5.71 mm.

Check the half-millimetre mark before adding the thimble reading. Correction means subtracting the signed zero error: subtracting a negative error increases the corrected reading. The aligned-scale practice requests two decimal places; do not assume the same precision for every real instrument.

Use a measured diameter in resistivity

Read the two scales

Take the last sleeve mark visible to the left of the thimble edge. Whole millimetres are above the reference line; half-millimetres are below. Add the aligned thimble division multiplied by 0.01 mm.

Correct a zero error

Zero error is the signed indication when the measuring faces touch. Corrected length = indicated reading − zero error. A positive error is subtracted. For a negative error, add its magnitude.

Resolution and recording

These diagrams use a 0.5 mm pitch and 50 divisions per turn: one division represents 0.01 mm. In these exercises, record readings to two decimal places in mm, keeping a final zero. Other micrometers can have different scales.

Resolution is the smallest detectable change in a reading. It does not give the total uncertainty on its own. In a real measurement, check the zero, use the ratchet for consistent contact and repeat measurements at different positions and orientations where appropriate.

Readings here align exactly with a scale division. The drawing is an enlarged scale close-up, not a full instrument or a model of contact pressure.

A-level relevance

AQA 7408: 7.1 AT e; required practical 5 (selected); OCR A H556: Practical apparatus; measurement conventions (selected). Tasks cover the selected skills listed above.

AQA specification · OCR practical skills handbook · AQA practical handbook

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