Absolute, gauge and differential pressure
A zero gauge reading need not be a vacuum.
Key knowledge
Gauge pressure is pressure relative to a stated reference, commonly local atmospheric pressure: p_g=p_abs−p_ref. A differential pressure compares two specified pressures. Absolute pressure uses a vacuum reference. A tank vented to the atmosphere can have zero atmospheric-gauge pressure while its absolute pressure remains atmospheric.
Values and equations
p_g=p_abs−p_ref; Δp=p_A−p_B
- p_g,p_abs,p_ref,p_A,p_B,Δp
- Gauge, absolute, reference, compared and differential pressures Pa
Conditions and scope
- Use the same pressure units and state the actual reference pressure.
- Negative gauge pressure does not imply negative absolute pressure. The familiar nonnegative absolute-pressure assumption applies to ordinary equilibrium gas pressure; liquids under tensile metastable conditions need a separate physical model.
Sources · 2
References
Sources retain their recorded scope. A source link alone does not establish verification of every statement.
- University Physics Volume 1, §14.2: measuring pressureSamuel J. Ling, Jeff Sanny and William Moebs — OpenStax, Rice University, University Physics (2016)Textbook chapter
- Negative Pressure in Water Capillary Bridges at Nanocontacts (2017), NIST publication abstractSeung H. Yang, Michael Nosonovsky, Huan Zhang and Koo-Hyun Chung — NIST publication record / Nano LettersResearch abstract
Evidence and review
Read §14.2 Gauge Pressure versus Absolute Pressure and relation14.10. Retain the reference convention; exclude the oversimplified blanket statement that every fluid’s absolute pressure can never be negative. The directly read NIST2017 publication abstract explicitly describes absolute negative pressure as tensile stress in a potentially metastable water capillary bridge; abstract only, no full-paper model or numerical threshold claimed.
2026-10-10 · /root/audit_life_earth_chemistry — independent Chemistry/Life/Earth editor. Independent AI editorial review of this entry's statements, equations, applicability conditions and source coverage. Source checks apply to these claims within their stated limits.
Entry details
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- foundation-physics-absolute-gauge-pressure
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- foundations-refresh.1
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