= 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>.<High Precision Actuators with Closed-Loop Feedback Motor by Physik Instrumente>[M-221–M-226 description and technical-data table]{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 is
$$
\delta x=\frac{p_s}{GC}=10\,\mathrm{nm}.
$$
A 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.<Serial Block-Face Scanning Electron Microscopy to Reconstruct Three-Dimensional Tissue Nanostructure by Winfried Denk and Heinz Horstmann>[Materials and Methods, Microtome, specimen-advance mechanism and section-thickness calculation]{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.
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