Bellows as a transducer: What physical conversion does a mechanical bellows perform in instrumentation and control applications?

Introduction / Context:
Bellows are common primary sensing elements in process instrumentation. Understanding what they convert helps in selecting appropriate secondary transducers (e.g., potentiometers, LVDTs) for complete measurement chains.

Given Data / Assumptions:

• Bellows are flexible, sealed, accordion-like elements.
• Differential pressure is applied across the bellows walls.
• Motion is constrained along a single axis producing axial extension or compression.

Concept / Approach:
When a pressure difference acts across the effective bellows area, a force F = ΔP × A is generated. Balanced by spring stiffness and mechanical resistance, this force causes a measurable axial displacement proportional to ΔP over a calibrated range. The bellows by itself is a pressure-to-displacement converter; an additional transducer (e.g., LVDT) then converts displacement to voltage if needed.

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