How does a bourdon tube function?

• A. It's a curved metal tube that deforms upon pressure change
• B. It uses a diaphragm that flexes with pressure
• C. It relies on a capillary filled with liquid
• D. It measures pressure by digital sensing

Answer: (A)

Bourdon tubes convert pressure into mechanical motion through the elastic deformation of a curved metal tube. When the inside pressure increases, the curved tube tends to straighten, and that change in curvature drives a linkage that moves a needle on a dial. This simple, rugged mechanism uses the tube’s stiffness and geometry to translate pressure into readable movement without electronics.

This isn’t a diaphragm-based gauge, which uses a flexible membrane that deflects with pressure; nor a capillary-style gauge, which relies on a liquid column to indicate pressure; nor a digital sensor, which would convert pressure into an electronic signal.