A Buyer's Guide To Pressure Gauges

Introduction to Pressure Gauges

Pressure gauges are among the most common instruments in industrial facilities, yet selecting the right gauge for a specific application requires careful consideration of multiple factors. This buyer's guide will help you navigate the key specifications and make an informed selection.

Types of Pressure Gauges

Bourdon Tube Gauges

The most common type of pressure gauge, Bourdon tube gauges use a curved tube that straightens under pressure to drive a pointer mechanism. They are available in a wide range of pressure ranges and are suitable for most general industrial applications.

*Advantages:*

• Simple, robust construction
• Wide pressure range availability
• Low cost
• No external power required

*Limitations:*

• Not suitable for pulsating pressures without dampening
• Limited accuracy compared to digital gauges
• Not suitable for very low pressures

Diaphragm Gauges

Diaphragm gauges use a flexible membrane to measure pressure. They are ideal for:

• Low pressure measurement (below 15 PSI)
• Viscous or corrosive media
• Applications where the process must be isolated from the gauge mechanism

Digital Pressure Gauges

Digital gauges offer superior accuracy and additional features:

• Accuracy typically ±0.1% to ±0.5% of full scale
• Min/max recording
• Peak hold function
• Data logging capability
• Backlit displays for dark environments

Key Selection Criteria

Pressure Range

Select a gauge with a range where your normal operating pressure falls between 25% and 75% of full scale. This ensures adequate accuracy and prevents overpressure damage.

Accuracy Class

Pressure gauge accuracy is expressed as a percentage of full scale:

• *Grade 4A (±0.1%)*: Laboratory and precision applications
• *Grade 3A (±0.25%)*: High-accuracy industrial applications
• *Grade 2A (±0.5%)*: General industrial use
• *Grade A (±1%)*: Commercial and HVAC applications
• *Grade B (±2%)*: Rough service and general indication

Wetted Materials

The materials in contact with your process fluid must be compatible with the fluid's chemical properties, temperature, and pressure:

Process Connection

Common process connections include:

• *NPT (National Pipe Thread)*: Standard in North America
• *BSP (British Standard Pipe)*: Common in Europe and Asia
• *Flanged connections*: For large bore or high-pressure applications
• *Sanitary connections*: Tri-clamp or DIN for food and pharmaceutical

Environmental Rating

Consider the environment where the gauge will be installed:

• *IP54*: Dust and splash protected (indoor industrial)
• *IP65*: Dust-tight and water jet protected (outdoor)
• *IP67*: Immersion protected (washdown applications)
• *ATEX/IECEx*: Required for hazardous area installations

Special Considerations

Pulsating Pressure

For applications with pressure pulsations (pumps, compressors), use gauges with:

• Liquid-filled cases (glycerin or silicone oil) to dampen pointer movement
• Snubbers to protect the Bourdon tube from pressure spikes
• Stainless steel Bourdon tubes for better fatigue resistance

High Temperature Applications

For process temperatures above 150°F (65°C):

• Use a siphon or pigtail to protect the gauge from hot steam
• Consider remote diaphragm seals with capillary tubing
• Ensure the gauge case material is rated for the ambient temperature

Conclusion

Selecting the right pressure gauge requires matching the instrument specifications to your specific application requirements. When in doubt, consult with Instrivo's applications engineers — we're here to help you make the right selection the first time.

Browse our complete selection of pressure gauges from leading manufacturers including Ashcroft, Wika, and Winters.