A vernier scale is a visual aid to take an accurate measurement  reading between two graduation markings on a linear scale by using  mechanical interpolation; thereby increasing resolution and reducing  measurement uncertainty by using vernier acuity to reduce human  estimation error.

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A micrometer, sometimes known as a micrometer screw gauge, is a  device incorporating a calibrated screw widely used for accurate  measurement of components in mechanical engineering and machining as  well as most mechanical trades, along with other metrological  instruments such as dial, vernier, and digital calipers.