Which primary element is compact and used in small pressure ranges?

Which primary element is compact and used in small pressure ranges?

• A. Diaphragm
• B. Bourdon Tube
• C. Capsule
• D. Bellows

Answer: (C)

For very small pressure ranges, you want an element that responds with noticeable movement in a tiny, compact package. The capsule accomplishes this by using two thin diaphragms forming a small sealed cavity. When pressure is applied, the walls flex just enough to produce a measurable displacement, and the overall assembly remains very compact. That combination—high sensitivity in a small footprint—makes the capsule the preferred primary element for low-pressure or vacuum measurements. Bourdon tubes are thick and bulky, suited for higher pressures; bellows can be sensitive but typically take up more space for the same range; diaphragms alone are useful but don’t match the capsule’s compactness and sensitivity in ultra-low-pressure applications.

For very small pressure ranges, you want an element that responds with noticeable movement in a tiny, compact package. The capsule accomplishes this by using two thin diaphragms forming a small sealed cavity. When pressure is applied, the walls flex just enough to produce a measurable displacement, and the overall assembly remains very compact. That combination—high sensitivity in a small footprint—makes the capsule the preferred primary element for low-pressure or vacuum measurements.

Bourdon tubes are thick and bulky, suited for higher pressures; bellows can be sensitive but typically take up more space for the same range; diaphragms alone are useful but don’t match the capsule’s compactness and sensitivity in ultra-low-pressure applications.