A device used to measure small deformations in a crankshaft is called what?

• A. Strain gauge
• B. Dial indicator
• C. Micrometer
• D. Caliper

Answer: (A)

Measuring small deformations relies on sensing strain—the tiny change in length a material experiences under load. A strain gauge does exactly that: it’s a sensor bonded to the crankshaft surface that converts the material’s strain into a change in electrical resistance. This direct, localized signal allows precise measurement of how the shaft flexes, twists, or bends under operating loads, including fatigue phenomena. Dial indicators can detect small displacements, but they track surface movement rather than the material’s strain response, and they’re less suited for capturing the minute, distributed strains inside a rotating part. Micrometers and calipers measure static dimensions (diameter, thickness) rather than deformation under load, so they don’t provide the same insight into how the crankshaft deforms. That's why strain gauge is the best choice for this purpose.