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Bourdon Tube vs. Capsule Pressure Gauges: What's the Difference?


Pressure gauges are among the most widely used instruments in industrial, commercial, HVAC, and process applications. Selecting the correct gauge technology is critical for ensuring accurate measurements, reliable performance, and long service life.

Two of the most common mechanical pressure measurement technologies are Bourdon tube pressure gauges and capsule pressure gauges. While both measure pressure, they are designed for very different operating ranges and applications.

This guide explains the differences between Bourdon tube and capsule pressure gauges, their pressure ranges, common applications, and the styles available from Merit Instruments.


What is a Bourdon Tube Pressure Gauge?

A Bourdon tube pressure gauge uses a curved metal tube that tends to straighten when internal pressure is applied. This mechanical movement is transferred through a gear mechanism to a pointer that indicates pressure on the dial.

Invented in the 19th century, the Bourdon tube remains the most widely used pressure measurement technology worldwide due to its durability, accuracy, and broad pressure range.


How a Bourdon Tube Gauge Works

  1. Process pressure enters the gauge through the connection.

  2. Pressure fills the curved Bourdon tube.

  3. The tube attempts to straighten as pressure increases.

  4. Mechanical linkage converts tube movement into pointer rotation.

  5. The pointer displays pressure on the dial.


Bourdon Tube Pressure Ranges

Bourdon tube gauges are ideal for medium to high-pressure applications and are commonly available in ranges from:

  • Vacuum to 0 psi

  • 0-15 psi

  • 0-30 psi

  • 0-60 psi

  • 0-100 psi

  • 0-300 psi

  • 0-600 psi

  • 0-1,000 psi

  • 0-5,000 psi

  • Up to 20,000 psi and beyond for specialized applications


Typical Bourdon Tube Applications

  • Industrial process systems

  • Hydraulic equipment

  • Pneumatic systems

  • Pumps and compressors

  • HVAC systems

  • Water treatment facilities

  • Chemical processing

  • Oil and gas equipment

  • Manufacturing machinery


Advantages of Bourdon Tube Gauges

✔ Wide pressure measurement range

✔ Rugged construction

✔ Excellent long-term reliability

✔ Available in numerous materials

✔ Cost-effective solution

✔ Suitable for vibration-resistant and liquid-filled designs


What is a Capsule Pressure Gauge?

A capsule pressure gauge is specifically designed for measuring extremely low pressures and vacuum conditions.

Instead of a Bourdon tube, these gauges utilize two thin metal diaphragms welded together to form a capsule. Small pressure changes cause the capsule to expand or contract, creating movement that drives the pointer.

Because the sensing element is highly sensitive, capsule gauges can accurately measure very low pressures that would be difficult or impossible for standard Bourdon tube gauges to detect.


How a Capsule Pressure Gauge Works

  1. Low pressure enters the capsule chamber.

  2. The capsule expands or contracts based on pressure changes.

  3. Mechanical linkage amplifies the movement.

  4. The pointer displays the pressure reading.


Capsule Pressure Ranges

Capsule gauges are designed for low-pressure applications, typically covering:

  • 0-10 mbar

  • 0-25 mbar

  • 0-60 mbar

  • 0-100 mbar

  • 0-160 mbar

  • 0-250 mbar

  • 0-400 mbar

  • 0-600 mbar

Equivalent ranges may also be available in:

  • Inches of Water Column (inWC)

  • Inches of Mercury (inHg)

  • Ounces per Square Inch (oz/in²)

  • Kilopascals (kPa)


Typical Capsule Gauge Applications

  • Natural gas distribution

  • Burner systems

  • HVAC airflow monitoring

  • Air handling units

  • Clean rooms

  • Ventilation systems

  • Dust collection equipment

  • Filter monitoring

  • Laboratory applications


Advantages of Capsule Pressure Gauges

✔ Exceptional sensitivity

✔ Accurate low-pressure measurement

✔ Ideal for gas and air applications

✔ Suitable for vacuum measurement

✔ Easy-to-read low-pressure scales


Bourdon Tube vs. Capsule Pressure Gauges: Side-by-Side Comparison

Feature

Bourdon Tube Gauge

Capsule Gauge

Pressure Range

Medium to Very High

Very Low

Typical Units

psi, bar, kPa, MPa

mbar, inWC, oz/in²

Best For

Industrial processes

Low-pressure gas and air systems

Durability

Extremely rugged

More sensitive

Vacuum Measurement

Limited models

Excellent

Common Industries

Industrial, OEM, HVAC, Oil & Gas

HVAC, Gas Distribution, Air Handling

Merit Instruments Bourdon Tube Pressure Gauges

Merit Instruments offers a comprehensive range of Bourdon tube pressure gauges designed for OEM, industrial, commercial, and HVAC applications.


Dry Utility Pressure Gauges

Economical gauges ideal for general-purpose pressure measurement.

Features:

  • Steel or stainless steel cases

  • Bottom or back connection

  • Multiple dial sizes

  • PSI, kPa, bar, and dual scales


Liquid-Filled Pressure Gauges

Designed to withstand vibration and pulsation.

Benefits include:

  • Improved pointer stability

  • Longer service life

  • Enhanced readability

  • Reduced wear on internal components


Stainless Steel Pressure Gauges

Engineered for harsh environments and corrosive media.

Applications include:

  • Chemical processing

  • Food and beverage

  • Water treatment

  • Industrial manufacturing


Custom-Branded OEM Gauges

Merit Instruments specializes in:

  • Private-label pressure gauges

  • Custom dial designs

  • White-label instrumentation

  • Distributor branding programs

  • OEM product development


Merit Instruments Capsule Pressure Gauges

Merit's capsule pressure gauges are designed for accurate low-pressure measurement in HVAC, gas distribution, and process control applications.

Available options include:

  • Dry capsule gauges

  • Low-pressure air gauges

  • Vacuum and compound ranges

  • Custom dial scales

  • Dual-scale configurations

  • OEM branding solutions

Common measurement units include:

  • Inches Water Column (inWC)

  • Millibar (mbar)

  • Kilopascal (kPa)

  • Ounces per Square Inch (oz/in²)


Which Pressure Gauge Should You Choose?

Choose a Bourdon tube gauge if your application involves:

  • Water systems

  • Hydraulic pressure

  • Compressed air

  • Industrial equipment

  • Pressures above approximately 600 mbar (9 psi)

Choose a capsule pressure gauge if your application involves:

  • Low-pressure air measurement

  • Natural gas systems

  • HVAC airflow monitoring

  • Filter differential pressure

  • Ventilation systems

  • Pressures below approximately 600 mbar (9 psi)

Selecting the proper sensing technology ensures accurate readings, improved reliability, and reduced maintenance costs.


Partner with Merit Instruments

Merit Instruments provides high-quality pressure gauges for industrial, HVAC, OEM, and private-label applications throughout North America.

Whether you require a rugged Bourdon tube gauge for demanding industrial service or a sensitive capsule gauge for low-pressure air and gas applications, Merit Instruments offers dependable solutions backed by responsive customer support and custom branding capabilities.

Contact Merit Instruments today to discuss your pressure measurement requirements and discover how our private-label and OEM programs can help strengthen your brand while delivering proven instrumentation performance.



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