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Micrometer reading practice

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

Practise

Scale resolution

What change in length does one thimble division represent, in mm?

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: 0.00 mm. Thimble division at the reference line: 3. Pitch 0.5 mm; 50 divisions per turn.00510Sleeve / mmThimble
Scale close-up: whole millimetres above the sleeve reference line, half-millimetres below.
Scale text alternative

Last visible sleeve mark: 0.00 mm. Thimble division at the reference line: 3.

Larger micrometer
Last visible sleeve mark: 0.00 mm. Thimble division at the reference line: 3. Pitch 0.5 mm; 50 divisions per turn.00510Sleeve / mmThimble

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

Hint

Divide the advance per complete turn by the number of divisions.

Worked solution
  1. Resolution = 0.5 mm / 50 = 0.01 mm. Resolution alone does not specify the total measurement uncertainty.
  2. Answer: 0.01 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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