Low pressure measurement is one of those applications where choosing a pressure gauge only by dial size and connection can cause trouble.

A plant may need to monitor clean air pressure, low pressure draft, a gaseous line or a low viscosity process medium. The pressure may be only a few millibars, so the instrument has to provide useful indication in a range where a conventional high pressure gauge would not be the logical choice.

This is where a Baumer Capsule Pressure Gauge fits.

The Baumer capsule gauge range in the supplied datasheets is designed around low pressure measurement, with available ranges from 25 mbar to 600 mbar, pressure, vacuum and compound scale possibilities, several mounting styles and two useful construction choices: the AX SS Case Brass Pressure Gauge and the AF All SS Pressure Gauge.

The important part is deciding which construction is right for your process. The AX and AF may look similar from the front, but the materials, temperature capability, ingress protection and overpressure capability are not the same.

What is a Capsule Pressure Gauge?

A capsule pressure gauge is intended for measuring relatively low pressures where a more sensitive measuring element is required.

In general engineering terms, the pressure acts on a capsule sensing element. Small movement of this element is transferred through the mechanical movement to the pointer, giving a direct local reading on the dial.

For the Baumer models covered here, there is no electrical output specified in the supplied datasheets. These are mechanical indicating instruments intended for local pressure indication.

That distinction matters. If your requirement is only to see the pressure locally at a duct, vessel, utility line or process point, a capsule gauge may be suitable. If you need the pressure value inside a PLC, SCADA, BMS or remote control system, you would normally need an appropriate pressure transmitter or electronic measurement solution as well.

Why Capsule Gauges Matter in Actual Plant Conditions

When pressure is low, range selection becomes especially important.

Suppose the normal process pressure is around 150 mmWC. Installing a gauge designed for much higher pressure may technically give a reading, but the useful movement of the pointer can become too small for practical monitoring.

A properly selected capsule gauge gives the operator a scale that is actually useful for the process.

Baumer lists these gauges for applications including:

• Low pressure draft measurement
• Food and beverage plants
• Pharmaceutical applications
• Breweries
• Conventional power plants
• Nuclear power plants
• Clean air
• Gaseous media
• Low viscosity, non corrosive media that will not obstruct the pressure system

The datasheets specify ±1.6% of full scale accuracy for both AX and AF models.

For a maintenance engineer, this means the first question should not be "Which pressure gauge is cheapest?" It should be "What is the actual operating pressure, what media touches the instrument and what range gives me a useful reading?"

Baumer Capsule Pressure Gauge Range

The uploaded datasheets give two main constructions worth comparing.

Baumer AX Capsule Pressure Gauge

The Baumer AX is an SS case pressure gauge with copper alloy pressure components. It is a practical option where the process medium is compatible with copper alloy wetted parts and the application does not require an all stainless steel pressure system.

It also comes in four dial sizes, making it possible to choose a compact local gauge or a larger dial for easier reading from a distance.

Technical points to note:

• Available range: 25 mbar to 600 mbar
• Accuracy: ±1.6% of full scale
• Nominal sizes: 63, 100, 125 and 150 mm
• Case and bezel: AISI 304 stainless steel, bayonet type
• Capsule: copper alloy
• Socket: copper alloy
• Movement: copper alloy
• Joints: tin soldering
• Protection: IP55
• Ambient temperature: minus 25°C to plus 65°C
• Maximum process temperature: 100°C
• Recommended operating pressure: 75% of scale value
• Overpressure: listed as not suitable
• Zero adjustment provision
• General standard reference: EN 837-3

Where it is commonly suited:

• Low pressure air lines
• Draft measurement
• Clean gas service
• Utility monitoring
• HVAC related low pressure points
• Suitable brewery and food process utilities
• General plant low pressure monitoring

Baumer AF All Stainless Steel Capsule Pressure Gauge

The Baumer AF is the better option when stainless steel wetted parts, a higher process temperature limit or stronger ingress protection are required.

Its maximum listed process temperature is 150°C, compared with 100°C for the AX.

Technical points to note:

• Available range: 25 mbar to 600 mbar
• Accuracy: ±1.6% of full scale
• Nominal sizes: 63, 100, 125 and 150 mm
• Case and bezel: AISI 304 stainless steel
• Capsule: AISI 316 stainless steel
• Socket: AISI 316L stainless steel
• Movement: AISI 304 stainless steel
• Joints: TIG argon arc welding
• Protection: IP65, with IP55 for the 63 mm size
• Ambient temperature: minus 25°C to plus 65°C
• Maximum process temperature: 150°C
• Recommended operating pressure: 75% of scale value
• Overpressure: 130% of maximum scale value
• Zero adjustment provision
• General standard reference: EN 837-3

Where it is commonly suited:

• Pharmaceutical utility applications
• Food and beverage processing
• Breweries
• Clean air systems
• Suitable gas applications
• Process plant low pressure monitoring
• Applications requiring stainless steel wetted components

Baumer AX vs AF Capsule Pressure Gauge

The practical decision is straightforward. If the process is compatible with copper alloy components and the environmental conditions fit the AX specifications, AX may be sufficient. If stainless steel wetted parts, higher process temperature capability or better enclosure protection are important, AF becomes the stronger choice.

Pressure, Vacuum and Compound Ranges

Range selection deserves more attention than most buyers give it.

The Baumer datasheets show pressure scales such as:

• 0 to 250 mmWC
• 0 to 400 mmWC
• 0 to 600 mmWC
• 0 to 1000 mmWC
• 0 to 1600 mmWC
• 0 to 2000 mmWC
• 0 to 2500 mmWC
• 0 to 4000 mmWC
• 0 to 6000 mmWC

Vacuum and compound ranges are also listed.

Baumer notes that other national and international scales such as mbar, kPa, inWC, MWC, inHg and mmHg, along with dual or equivalent scales, can be provided according to requirement.

The selection lesson is important: do not choose the largest available range "for safety." A range that is unnecessarily high makes a low pressure process harder to read.

Mounting Options Matter More Than They Look

A replacement gauge can have the correct pressure range and still be wrong for the installation if the connection and mounting arrangement do not match.

The Baumer capsule range includes several configurations, depending on nominal size:

• Wall, surface or projection mounting with bottom entry
• Direct bottom entry
• Direct lower back entry
• Direct center back entry
• Lower back entry with front flange
• Lower back entry with mounting bracket
• Center back entry with mounting bracket

The dimensional drawings on pages 2 and 3 of the AX and AF datasheets show that the body depth, flange arrangement and mounting dimensions change with nominal size and mounting type. That is particularly important when replacing a gauge in an existing panel or machine.

Before ordering a replacement, check the old gauge from the side and rear, not just from the front.

Process Connections

The ordering tables provide connection options including:

• 1/4 inch BSP male
• 1/4 inch NPT male
• 3/8 inch BSP male
• 3/8 inch NPT male
• 1/2 inch BSP male
• 1/2 inch NPT male
• M20 x 1.5 male

The datasheets also note that other connection types can be provided on request, and that some connections for the 63 mm size are achieved through adaptors.

This is one of the easiest purchasing mistakes to avoid. Confirm the thread before placing the order.

Key Selection Factors for a Baumer Capsule Pressure Gauge

1. Actual working pressure

Start with the normal operating pressure, not only the maximum possible pressure. Both datasheets specify operating pressure at 75% of scale value.

2. Media compatibility

For AX, check compatibility with the copper alloy capsule and socket.

For AF, check compatibility with the AISI 316 capsule and AISI 316L socket.

3. Overpressure possibility

This is a major difference between the two models. AX is listed as not suitable for overpressure, while AF specifies 130% of maximum scale value.

4. Process temperature

AX has a maximum process temperature of 100°C.

AF extends this to 150°C.

5. Ambient condition and enclosure

Both models list an ambient range from minus 25°C to plus 65°C. For protection, AX is IP55, while AF is IP65 for the larger sizes and IP55 for 63 mm.

6. Dial size

Choose 63 mm where space is tight. Consider 100, 125 or 150 mm where the operator needs to read the gauge from farther away.

7. Mounting and connection

Confirm bottom entry, back entry, panel arrangement, flange or bracket requirement before ordering.

8. Required scale

Confirm whether your plant standard uses mbar, mmWC, kPa, inWC or another unit. Dual scales can also be requested according to the datasheet.

Common Mistakes to Avoid

Do This, Not That

Quick Selection Checklist

Before asking for a Baumer Capsule Pressure Gauge quotation, confirm:

1. Normal operating pressure
2. Required pressure, vacuum or compound range
3. Preferred engineering unit
4. Process media
5. Maximum process temperature
6. Possibility of pressure spikes or overpressure
7. Required dial size
8. Bottom or back connection
9. Mounting flange or bracket requirement
10. BSP, NPT or metric process connection
11. Required IP protection
12. Whether copper alloy or stainless steel wetted parts are acceptable
13. Calibration certificate requirement
14. Any custom dial or tag requirement

Optional Features Worth Confirming

The Baumer ordering tables also list options such as calibration certificates, traceable calibration certificates, plexiglass, safety glass, toughened glass, custom dial marking and stainless steel tag plates.

For the AF version, the datasheet also lists options such as material test certificates and an AISI 316 case and bezel for nominal sizes of 100 mm and above.

These options are worth discussing at quotation stage rather than after the gauge has already arrived.

Why Buy Baumer Capsule Pressure Gauges from Radical TechMart?

A low pressure gauge inquiry often begins with something simple such as "Need 100 mm capsule gauge, 0 to 600 mmWC."

But that is not always enough information to select the correct instrument.

At Radical TechMart, the focus is to help buyers check the application before finalizing the gauge, including pressure range, media, wetted material, dial size, mounting type, process connection and installation condition.

This is particularly useful for OEMs, plant maintenance teams, instrumentation engineers, EPC contractors and purchase departments that need a correct replacement or project specification rather than simply another gauge with a similar dial.

Final Thoughts

A Baumer Capsule Pressure Gauge makes sense when the application involves low pressure measurement and clear local indication.

The real selection decision is not AX versus AF based on price alone. It is about what touches the process, how hot the process can become, whether overpressure can occur, what protection level is required and how the gauge has to fit into the existing installation.

For compatible general service, the AX offers a stainless case with copper alloy pressure components. For applications needing stainless steel wetted parts, higher process temperature capability and stronger protection in larger sizes, the AF provides the more appropriate construction.

In low pressure measurement, choosing the correct range and construction is what makes the gauge useful after installation, not simply choosing a familiar model number.

FAQs

1. What is a Baumer capsule pressure gauge used for?

It is used for low pressure measurement in applications such as draft measurement, clean air, gaseous media and suitable low viscosity, non corrosive process media.

2. What pressure ranges are available for Baumer capsule gauges?

The datasheets state an available range from 25 mbar to 600 mbar. Example mmWC pressure, vacuum and compound ranges are also provided.

3. What is the difference between Baumer AX and AF capsule gauges?

AX uses a stainless steel case with copper alloy capsule and socket. AF uses an AISI 316 stainless steel capsule and AISI 316L socket, provides a higher listed process temperature and has IP65 protection for 100 mm and larger versions.

4. Is the Baumer AX suitable for pressure spikes?

The AX datasheet lists its overpressure limit as "Not Suitable." If pressure spikes are expected, this must be considered during selection.

5. What is the accuracy of Baumer capsule pressure gauges?

Both AX and AF datasheets specify accuracy of ±1.6% of full scale.

6. Which dial sizes are available?

Both models are available in standard nominal sizes of 63, 100, 125 and 150 mm.

7. Can I order the gauge in mmWC, mbar or kPa?

Yes. The datasheets reference scales including mbar, kPa, inWC, MWC, inHg and mmHg, along with dual or equivalent scales on request.

8. Can Baumer AX or AF connect directly to a PLC?

The supplied AX and AF datasheets describe mechanical indicating gauges and do not specify an electrical output. For PLC or SCADA pressure monitoring, an appropriate pressure transmitter or electronic pressure instrument should be selected separately.

A pressure gauge is one of the simplest instruments in a plant, but it is also one of the easiest to select incorrectly.

A maintenance team may ask for a 0 to 10 bar gauge with a bottom connection. That sounds complete, but it still leaves several important questions unanswered. What is the process media? Is the line vibrating? What process temperature will the gauge see? Is the pressure only a few hundred millibar? How far away will the operator read the dial?

These details decide whether you need a compact stainless steel Bourdon gauge, a larger industrial gauge for easier reading, or a capsule gauge specifically meant for low-pressure measurement.

Baumer offers different pressure gauge constructions for these requirements. The ADC and ADD models use an all stainless steel Bourdon measuring system, while the AXD, AXF and AXH models use a capsule measuring element with copper alloy wetted parts for low-pressure applications.

The right way to select between them is not by model number alone. Start with the application.

What Are Industrial Pressure Gauges?

Industrial pressure gauges provide a direct local indication of pressure at a machine, pipeline or process point.

You will commonly find them on:

• Pumps
• Compressors
• Hydraulic systems
• Refrigeration equipment
• Process lines
• Chemical equipment
• Utility skids
• Diesel engines
• Food processing equipment
• Pharmaceutical equipment

Unlike a pressure transmitter, a mechanical pressure gauge does not normally send an electrical signal to a PLC or SCADA system. Its main job is to give operators and maintenance teams an immediate pressure reading directly at the equipment.

This makes the gauge useful for startup checks, troubleshooting, preventive maintenance and routine operator rounds.

Bourdon Pressure Gauge or Capsule Pressure Gauge?

This is the first major selection decision.

Choose a Bourdon gauge when:

You are measuring normal industrial pressure on pumps, compressors, hydraulic systems, process lines or machinery.

Baumer ADC and ADD use a Bourdon measuring system with AISI 316L stainless steel for the socket and Bourdon element. Their standard construction is designed for demanding industrial pressure measurement.

Choose a capsule gauge when:

The pressure is very low and a conventional industrial pressure gauge is not the best fit.

The Baumer AX series is designed for low-pressure measurement. Available pressure ranges start from 25 mbar and extend to 600 mbar. Typical applications include clean air, gases, draft measurement and low-viscosity, non-corrosive media.

That means a pump discharge pressure point and a low-pressure air duct may both need a gauge, but they should not automatically use the same type.

Baumer Industrial Pressure Gauge Models

Baumer ADC All Stainless Steel Pressure Gauge

The Baumer ADC is a practical option when you need a compact pressure gauge for industrial machinery, pumps or equipment where installation space is limited.

Its 50 mm dial keeps the overall size small, while the stainless steel measuring system makes it suitable for industrial pressure applications where material compatibility matters.

The standard 50 mm version has an accuracy of ±2.5% of full scale. If the application requires easier reading or better accuracy, moving to the 63 mm ADD version may make more sense.

Technical points to note:

• Nominal size: 50 mm
• Measuring principle: Bourdon
• Accuracy: ±2.5% of full scale
• Case and bezel: AISI 304 stainless steel
• Socket: AISI 316L stainless steel
• Bourdon element: AISI 316L stainless steel
• Movement: AISI 304 stainless steel
• Standard protection: IP65
• Ambient temperature: -25°C to +65°C
• Standard process temperature: maximum 200°C
• Operating pressure: 75% of scale value

Where it is commonly used:

• Pumps
• Engine compressors
• Diesel engines
• Hydraulic systems
• Refrigeration equipment
• OEM machinery

Baumer ADD All Stainless Steel Pressure Gauge

The Baumer ADD is a better fit when you still want a compact industrial gauge but need a larger 63 mm dial and improved reading accuracy.

In practical maintenance work, the difference between a 50 mm and 63 mm dial can matter. Gauges are often installed below eye level, inside machinery or next to pumps and piping. Better dial visibility makes routine inspection easier.

The model can also be configured as a dry, fillable or glycerine-filled gauge depending on the installation condition.

For machinery with vibration or pressure pulsation, a liquid-filled configuration may improve pointer stability and reduce mechanical wear.

Technical points to note:

• Nominal size: 63 mm
• Measuring principle: Bourdon
• Accuracy: ±1.6% of full scale
• Case and bezel: AISI 304 stainless steel
• Socket and Bourdon: AISI 316L stainless steel
• Standard protection: IP65
• Optional IP66 and IP67 protection listed
• Standard process temperature: maximum 200°C
• Dry, fillable and glycerine-filled configurations available
• Multiple bottom-entry and back-entry mounting arrangements available

Where it is commonly used:

• Process pumps
• Compressor systems
• Hydraulic equipment
• Petrochemical plants
• Pharmaceutical equipment
• Food and beverage processes

Baumer AXD Capsule Pressure Gauge

The Baumer AXD is intended for applications where pressure is too low for the normal selection logic used with a Bourdon gauge.

With a 63 mm nominal size and capsule measuring element, it is well suited to compact low-pressure indication points.

Technical points to note:

• Nominal size: 63 mm
• Measuring principle: Capsule
• Accuracy: ±1.6% of full scale
• Case and bezel: AISI 304 stainless steel
• Capsule: Copper alloy
• Socket: Copper alloy
• Movement: Copper alloy
• Standard protection: IP55
• Ambient temperature: -25°C to +65°C
• Process temperature: maximum 100°C
• Operating pressure: 75% of scale value
• Zero adjustment provision

Where it is commonly used:

• Clean air pressure measurement
• Gas pressure indication
• Draft measurement
• Food processing equipment
• Pharmaceutical utilities
• Low-pressure process systems

Baumer AXF Capsule Pressure Gauge

AXF uses the same basic capsule pressure measuring concept as the AXD but increases the dial size to 100 mm.

That larger dial becomes useful when the pressure point is mounted farther away from the operator or when small pressure changes need to be read more comfortably.

The AX series supports multiple pressure, vacuum and compound scales, including units such as mbar, kPa, inWC, MWC, inHg and mmHg depending on the requirement.

Technical points to note:

• Nominal size: 100 mm
• Capsule measuring element
• Accuracy: ±1.6% of full scale
• AISI 304 stainless steel case
• Copper alloy capsule and socket
• IP55 protection
• Zero adjustment provision
• Maximum process temperature: 100°C
• Multiple bottom-entry, back-entry and flange mounting arrangements available

Where it is commonly used:

• Low-pressure utility systems
• Clean air lines
• Gas pressure monitoring
• Draft indication
• Food and beverage plants
• Pharmaceutical utilities

Baumer AXH Capsule Pressure Gauge

The Baumer AXH takes the same low-pressure capsule concept into a 150 mm nominal-size gauge.

This is useful when local pressure needs to be visible from a greater distance or when operators need a large, easy-to-read dial.

AXH retains the low-pressure capsule design, copper alloy measuring system and ±1.6% full-scale accuracy of the AX family.

Technical points to note:

• Nominal size: 150 mm
• Measuring principle: Capsule
• Accuracy: ±1.6% of full scale
• Stainless steel case and ring
• Copper alloy capsule
• Copper alloy socket
• IP55 protection
• Maximum process temperature: 100°C
• Zero adjustment provision
• Multiple mounting configurations available

Where it is commonly used:

• Plant utility systems
• Large process equipment
• Clean gas lines
• Draft measurement
• Low-pressure monitoring stations
• Applications requiring easy long-distance reading

ADC vs ADD vs AXD vs AXF vs AXH

Key Selection Factors for Industrial Pressure Gauges

1. Start with the actual pressure range

Do not select a gauge whose maximum scale is almost equal to normal operating pressure.

For the AD series, the recommended continuous operating pressure is 75% of the scale value. The gauge also has defined overpressure limits depending on the selected pressure range.

Give the gauge enough headroom for normal process variation.

2. Check whether the pressure is genuinely low

If the requirement is measured in tens or hundreds of millibar, a capsule gauge may be more appropriate than a standard Bourdon gauge.

This is where AXD, AXF and AXH become relevant.

3. Match the wetted material to the media

ADC and ADD use AISI 316L stainless steel for the socket and Bourdon element.

AX models use copper alloy for the capsule and socket.

That difference should be treated as a selection parameter, not just a construction detail.

4. Decide the dial size from viewing distance

A 50 mm dial works well on compact machines.

A 63 mm dial provides a useful balance between size and readability.

For low-pressure applications, 100 mm and 150 mm AX variants become useful when the gauge must be read from farther away.

5. Consider vibration and pulsation

A pump or compressor can produce a pointer that continuously fluctuates.

Where required, consider a liquid-filled configuration or suitable accessories such as a snubber. This helps stabilize the pressure indication under pulsating conditions.

6. Confirm process temperature

Do not check only ambient temperature.

The fluid entering the pressure connection can expose the gauge to much higher temperatures. For high-temperature services, accessories such as siphons or cooling elements may also need to be considered.

7. Confirm mounting and connection before ordering

Bottom entry, lower back entry, center back entry, flange mounting and bracket mounting are not interchangeable once the installation is fabricated.

The connection size and thread standard also need to match the process connection.

Common Mistakes to Avoid

Quick Selection Checklist

Before ordering an industrial pressure gauge, confirm:

1. What is the normal operating pressure?
2. What is the maximum possible pressure?
3. Is it pressure, vacuum or compound measurement?
4. Is the application low pressure?
5. What process media touches the gauge?
6. Are stainless steel wetted parts required?
7. What is the process temperature?
8. Is there vibration or pulsation?
9. What dial size can the operator read comfortably?
10. Is bottom or back entry required?
11. What is the thread and connection size?
12. Is a calibration certificate required?
13. Are IP66, IP67 or other protection options needed?
14. Is an accessory such as a snubber, siphon or gauge cock required?

Why Buy Industrial Pressure Gauges from Radical TechMart?

Pressure gauge selection becomes much easier when the inquiry includes the actual process details rather than only a model number.

At Radical TechMart, the focus is to help customers select pressure instruments according to application, measuring range, media, material, mounting and installation condition.

Support is available for OEMs, maintenance teams, factories, EPC contractors, project engineers and purchase departments looking for Baumer pressure gauges and other industrial pressure instruments.

If you are replacing an existing gauge, sharing the old model number, pressure range, connection, dial size and application can help narrow down the suitable replacement much faster.

Final Thoughts

The difference between ADC, ADD, AXD, AXF and AXH is not simply dial size.

ADC and ADD are better suited to conventional industrial pressure measurement using an all stainless steel Bourdon measuring system. AXD, AXF and AXH move into low-pressure measurement using a capsule mechanism, with dial size increasing according to the visibility requirement.

The best pressure gauge is the one that matches the process pressure, media, operating temperature, mounting arrangement and the way the maintenance team will actually use it.

In industrial applications, correct pressure gauge selection saves much more than the cost of replacing a wrong instrument. It makes daily inspection easier, reduces premature failure and gives operators a pressure reading they can actually trust.

FAQs

1. What is the difference between Baumer ADC and ADD pressure gauges?

Both use an all stainless steel Bourdon measuring system. ADC is the 50 mm version with ±2.5% full-scale accuracy, while ADD is the 63 mm version with ±1.6% full-scale accuracy and better dial readability.

2. When should I use a capsule pressure gauge?

A capsule gauge is useful for low-pressure applications such as clean air, gas and draft measurement. The Baumer AX range is designed for low pressures from 25 mbar to 600 mbar.

3. What is the difference between AXD, AXF and AXH?

The main difference is nominal dial size. AXD is 63 mm, AXF is 100 mm and AXH is 150 mm. Larger dial sizes are useful when the gauge needs to be read from farther away.

4. Can Baumer industrial pressure gauges be glycerine filled?

The AD series includes dry, fillable and glycerine-filled configuration options. Liquid filling can be useful where vibration or pulsation affects pointer stability.

5. Can these pressure gauges connect directly to PLC or SCADA?

These are mechanical pressure gauges intended primarily for local pressure indication. For electrical signal transmission to a PLC, HMI or SCADA system, consider a pressure transmitter or an appropriate electronic pressure instrument.

6. How do I choose the correct pressure gauge range?

Select a range that keeps normal operating pressure comfortably below full scale. Also consider startup pressure, process fluctuations and possible pressure spikes before finalizing the range.

7. Is stainless steel construction always necessary?

Not always. It depends on process media, environment and application. However, wetted-part compatibility should always be checked. A stainless steel case alone does not mean the internal measuring parts are stainless steel.

8. What details should I provide when asking for a pressure gauge quotation?

Provide pressure range, media, dial size, process connection, mounting type, process temperature, required accuracy, dry or filled preference and any calibration requirement.