Backlash in gear sets is typically measured with which instrument?

• A. Dial indicator.
• B. Multimeter
• C. Oscilloscope
• D. Micrometer calibrated in inches

Answer: (A)

Backlash is the small clearance between mating gear teeth that allows one gear to move a little before engaging the other. Measuring this requires detecting tiny linear movements as the gear train is moved back and forth under a set preload. A dial indicator is ideal because it converts those small displacements into a precise, readable dial value, letting you quantify the play in thousandths of an inch (or hundredths of a millimeter). In a typical setup, you fix one gear or housing, apply a known load to the gears in one direction until contact is snug, then reverse direction and measure the movement until contact is reestablished; the indicator reading is the backlash.

The other instruments aren’t suitable for this specific measurement: a multimeter and an oscilloscope track electrical signals or waveforms, not mechanical play between teeth, and a micrometer measures a single dimension such as diameter or thickness, not the free movement between gears.