Which pressure-sensing device uses a curved tube that tends to straighten as pressure increases to move a dial?

Which pressure-sensing device uses a curved tube that tends to straighten as pressure increases to move a dial?

• A. Bourdon tube
• B. Diaphragm gauge
• C. Capsule gauge
• D. Bellows gauge

Answer: (A)

The concept hinges on converting pressure into a linear movement that drives a dial. A curved Bourdon tube does exactly that: when internal pressure rises, the elastic, circular or helical tube tends to straighten. That change in shape creates a displacement at the tube’s end, which is linked through a mechanical linkage to the pointer on the gauge dial, showing the pressure value. This straightening action with increasing pressure is the hallmark of the Bourdon tube gauge. Other pressure-sensing elements work differently. A diaphragm gauge uses a flexible membrane that deflects under pressure, and the movement of that membrane is translated to the dial. A capsule gauge relies on two diaphragms forming a capsule that expands with pressure. A bellows gauge uses folded bellows that expand or contract with pressure. None of these depend on a curved tube that straightens to move a dial, which is why the Bourdon-tube mechanism is the correct choice.

The concept hinges on converting pressure into a linear movement that drives a dial. A curved Bourdon tube does exactly that: when internal pressure rises, the elastic, circular or helical tube tends to straighten. That change in shape creates a displacement at the tube’s end, which is linked through a mechanical linkage to the pointer on the gauge dial, showing the pressure value. This straightening action with increasing pressure is the hallmark of the Bourdon tube gauge.

Other pressure-sensing elements work differently. A diaphragm gauge uses a flexible membrane that deflects under pressure, and the movement of that membrane is translated to the dial. A capsule gauge relies on two diaphragms forming a capsule that expands with pressure. A bellows gauge uses folded bellows that expand or contract with pressure. None of these depend on a curved tube that straightens to move a dial, which is why the Bourdon-tube mechanism is the correct choice.