Technical Resources & Guides
Practical pressure measurement fundamentals, selection checklists, and field installation best practices.
Written by instrumentation engineers for plant managers, OEM machinery designers, and automation technicians.
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Gauge vs. Absolute Pressure: How to Choose
ACT Sensors Application Engineering Knowledge Base
Every pressure measurement is a relative differential measurement against a reference datum. Selecting whether your sensor references local atmospheric air (Gauge) or a sealed zero-vacuum cavity (Absolute) fundamentally changes your readings across altitude and weather changes.
KEY TECHNICAL PRINCIPLES
- 1Gauge Pressure (barg / psig): Vented to current atmospheric pressure (1013 mbar at sea level). Reads 0 bar when open to air. Best for open tanks, pipe networks, and compressors.
- 2Sealed Gauge: References a fixed 1 bar sealed reference chamber. Used for high pressure (>20 bar) where weather atmospheric variations are negligible.
- 3Absolute Pressure (bara / psia): References a hard vacuum (0 bar absolute). Measures total internal pressure including atmosphere. Mandatory for vacuum distillation, barometers, and altitude testing.
TECHNICAL COMPARISON MATRIX
| Pressure Type | Reference Datum | Atmospheric Effect | Typical Industrial Applications |
|---|---|---|---|
| Gauge (Relative) | Ambient Atmospheric Pressure | Reads 0 at ambient; changes with weather | Pumps, compressors, hydraulic lines, general piping |
| Absolute | Absolute Zero Vacuum (0 bar) | Unchanged by local weather or altitude | Condenser vacuum, distillation columns, altitude test chambers |
| Sealed Gauge | Internal 1.013 bar Sealed Cavity | Eliminates atmospheric vent hole ingress | Heavy hydraulics (>25 bar), marine splash, washdown areas |
For pressures below 10 bar, always use vented Gauge pressure unless specifically monitoring a sealed vacuum cycle. Above 25 bar, Sealed Gauge is preferred to eliminate moisture ingress through the cable vent tube.
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Phase 2 Kansai, Ambernath Industrial Area, Ambernath West,
Thane - 421501, Maharashtra, India
Every sensor dispatched from ACT Sensors Pvt. Ltd. undergoes rigorous testing and individualized calibration certificates traceable to national metrological standards.