vernier dial

Gordon sweated, bending tensely over the bank of vernier dials.

Tom turned and adjusted a vernier dial newly mounted on the panel; this fed power to the repelatron.

Multhaus, the Chief Powerman's Mate, sat behind the emergency board, a vernier dial in each hand and both eyes on an oscilloscope screen.

This is similar to the manual machine tool method of clamping a micrometer onto a reference beam and adjusting the Vernier dial to zero using that object as the reference.

A Hewlett-Packard, Tektronix, or Fluke product might have metal vernier dials or ten-turn pots with digital readouts, while a Heathkit might use a simple plastic pointer and a scale silk-screened onto the front panel.