Mechanical vs manometric pressure elements Which of the following is <em>not</em> a mechanical elastic pressure sensing element?

Introduction / Context:
Pressure measurement employs two broad families of primary elements: (1) mechanical elastic elements that deflect (Bourdon tubes, diaphragms, bellows), and (2) hydrostatic columns/manometers (U-tubes, inclined manometers). Distinguishing these is foundational for selecting transmitters and gauges.

Given Data / Assumptions:

• Focus on the sensing element itself, not the dial or transducer.
• Mechanical elastic elements store strain energy and translate it into displacement.
• Manometers rely on fluid columns and hydrostatic balance.

Concept / Approach:
Bourdon tubes, diaphragms, and bellows are elastic metal elements that deform under pressure and are linked to pointers or transducers. A U-tube manometer is not an elastic element; it measures pressure from the height difference of a fluid column relative to a reference. Therefore, among the choices, the U-tube is not a mechanical elastic pressure element.

Step-by-Step Solution:

Verification / Alternative check:
Instrumentation catalogs group Bourdon/diaphragm/bellows gauges separately from manometers.

Why Other Options Are Wrong:

• Bourdon / Diaphragm / Bellows: All are classic elastic elements.

Common Pitfalls:
Calling any non-electronic device “mechanical”; the criterion here is elastic deflection versus hydrostatic balance.

Final Answer:
U-tube