 Motorized micrometer

A motorized micrometer uses a controlled motor to drive a precision screw and produce small linear motion. A typical design combines a lead screw, reduction gearing and a rotary encoder; the encoder may sense the motor shaft rather than the final load. The manufacturer's M-222–M-226 description makes this arrangement explicit and lists design resolution separately from minimum incremental motion, repeatability and backlash.^[ref]

For an original ideal drive, let screw pitch be $p_s=0.50\mathrm{mm}$ per screw revolution, reduction $G=100$ motor revolutions per screw revolution and encoder count $C=500$ per motor revolution. The nominal output increment per count isA reducing lever with motion ratio 0.11 would give $1.1\mathrm{nm}$ at its output per count. This is a kinematic increment, not demonstrated positioning accuracy. Compliance, backlash and instrumental drift can all exceed it.

A concrete experimental use advanced the specimen of an in-chamber ultramicrotome. Its 0.11 reduction transformed a quoted micrometer position measurement uncertainty of $50\mathrm{nm}$ into a $5.5\mathrm{nm}$ contribution at the specimen. The paper calculated nominal section thickness from the micrometer change and reduction ratio.^[ref] That contribution is not a complete measured section-thickness uncertainty. An independent displacement check and reversals of motion help assess the actual response of an assembled mechanism.