Pressure Measurement — Manometer Capability Can a manometer be configured to measure vacuum (negative gauge) pressures as well as positive gauge pressures?

Introduction / Context: Manometers are fundamental devices for measuring pressure differences using hydrostatic columns. With appropriate connection and reference, they can indicate pressures above or below atmospheric pressure (gauge positive or vacuum/negative gauge).

Given Data / Assumptions:

• U-tube or inclined manometer with a suitable manometric fluid (e.g., mercury, water, oil).
• One leg can be open to atmosphere; the other connected to the system point.
• Hydrostatic equilibrium applies, neglecting capillary corrections at macroscales.

Concept / Approach: The manometer measures pressure difference via Δp = ρ_m g Δh (adjusted for fluid columns). If the system pressure is below atmospheric, the meniscus moves opposite to the positive case, and the indicated height difference corresponds to a vacuum (negative gauge) value. Thus, by reading Δh and sign, vacuum is readily measured.

Step-by-Step Reasoning:

Verification / Alternative check: Industrial vacuum lines routinely use mercury or oil manometers and Bourdon gauges scaled for negative gauge pressure, confirming practicality.

Why Other Options Are Wrong: “Disagree” ignores common practice and the symmetric operation of manometers around atmospheric reference.

Common Pitfalls: Misreading sign conventions; using an inappropriate manometric fluid (too light or hazardous); neglecting capillary or temperature corrections in precise work.

Final Answer: Agree — manometers measure both vacuum and positive gauge pressures.