In many industrial processes, sudden pressure spikes—from water hammer, startup surges, pump cycling or valve events—can place measurement instruments under extreme stress. When a gauge cannot withstand these surges, the result is often permanent damage, unexpected downtime and avoidable maintenance costs. Overpressure gauges are designed to prevent those failures by protecting the Bourdon tube from deformation during high-pressure events.

With more than 170 years of experience solving pressure measurement challenges, Ashcroft understands how demanding these conditions can be. We design gauges that maintain accuracy, survive extreme upsets and help operators protect critical equipment.

Read this article to learn how two pressure gauges equipped with Ashcroft’s XRA built-in overpressure protection—the 1209 and T6500—compare in performance, construction, features and suitability for different industrial environments.

What Problems Do Overpressure Gauges Solve in Industrial Systems?

Overpressure conditions occur when a system experiences sudden or unintended changes in pressure. These events can be triggered by several common process conditions, including:

• Water hammer (a pressure surge caused when moving fluid is forced to stop or change direction abruptly)
• Rapid pump starts or shutdowns
• Valve closures or quick-actuating valves
• Sudden changes in flow or load conditions
• Equipment or control system malfunctions
   

Pressure instrumentation can only operate within its specified range. When processes exceed that range, the Bourdon tube can permanently deform, causing:

• Premature gauge failure
• Loss of calibration
• Internal component damage
• Potential safety risks and potential leak points
   

These risks highlight the importance of selecting an overpressure gauge capable of absorbing pressure spikes without losing accuracy or mechanical integrity.

How Does Built-In Overpressure Protection Work?

Ashcroft engineered an internal overpressure protection mechanism (XRA) to protect the Bourdon tube when system pressure exceeds the gauge’s normal operating range. This option is available on Ashcroft's 1209 Pressure Gauge and T6500 XRA Pressure Gauge.

When the gauge approaches full-scale pressure, the XRA mechanism restricts additional Bourdon tube movement. This changes the tube’s spring rate and prevents permanent deformation during extreme pressure events.

This built-in capability allows the instrument to absorb temporary pressure spikes without damage, reducing the need for external pressure limiting valves and helping extend instrument life.

How operators know when the gauge is in the overpressure zone

A visual cue on the XRA dial helps operators recognize unsafe conditions and assess whether a different range or protection strategy is required. XRA gauges include a red dial band:

• The white measurement zone shows normal operating pressure.
• The red zone indicates the system has exceeded the gauge’s intended range.

How Does the 1209 XRA Gauge Perform Under Overpressure?

The Ashcroft®1209 Pressure Gauge is a solid front, stainless-steel pressure gauge designed for safety, durability and corrosion resistance. With the XRA option, it becomes a strong choice for processes with significant or unpredictable pressure excursions.

1209 XRA Key Features and Benefits

• Up to 417% overpressure protection
  Survives severe pressure spikes without permanent damage, reducing downtime.
• Solid-front case with full pressure-relief back
  Directs energy away from the operator if a rupture occurs.
• ±0.5% of span accuracy (ASME Grade 2A)
  Supports precise readings in critical or high-value systems.
• 4½-inch dial
  Improves readability from longer distances.
• Red overpressure dial band
  Visually alerts operators to excursions beyond the rated range.
• Optional PLUS!™ Performance or liquid fill
  Reduces pointer flutter in vibration-intense environments, improving readability and extending gauge life.
• 316L stainless-steel construction
  Provides strong corrosion resistance for harsh process conditions.
• Welded socket-to-case design
  Improves leak integrity where containment is essential.

Common 1209 XRA Overpressure Applications

• Oil & Gas: wellhead monitoring, injection skids, separator units
• Chemical Processing: corrosive media transfer lines, reactor feed systems
• Power Generation: boiler feedwater systems, auxiliary steam lines
• Pulp & Paper: digesters, bleaching systems, recovery operations
• Food & Beverage: high-pressure CIP systems, sterilization lines
• OEM Equipment: hydraulic power units, high-pressure pump skids
   

How Does the T6500 XRA Gauge Perform Under Overpressure?

The Ashcroft® T6500 XRA Pressure Gauge is a rugged, solid-front gauge designed for demanding process industries. When equipped with the XRA option, it provides durable and reliable performance in environments with vibration, weather exposure or mechanical shock.

T6500 XRA Key Features and Benefits

• Up to 400% overpressure protection
  Allows the gauge to withstand severe and sudden surges in pressure.
• Solid front case with full rear blowout back
  Enhances operator safety by venting rupture energy away from the front.
• ±1% accuracy standard; ±0.5% optional
  Supports both general-purpose and higher-accuracy applications.
• 100 mm or 160 mm dial options
  Accommodates panel layouts, equipment size limitations and visibility needs.
• IP66 / NEMA 4X protection
  Enables use in washdown areas, outdoor installations and environments with dust or water exposure.
• Optional PLUS!™ Performance
  Dampens vibration and pulsation for stable, readable measurements.
• Stainless-steel case and wetted parts
  Provides strong corrosion resistance suitable for most process environments.
• Red overpressure dial band
  Offers clear visual indication of pressure excursions.
• Welded system design
  Improves durability under high-cycle and high-vibration loading.
   

Common T6500 XRA Overpressure Applications

• Offshore Oil & Gas: mud pumps, choke/kill manifolds, stimulation equipment
• Chemical & Petrochemical: compressor discharge lines, reaction systems
• Power Generation: turbine lube oil systems, cooling water skids
• Pulp & Paper: washdown systems, digester feed lines
• Industrial Machinery: hydraulic presses, pump packages
• Food & Beverage: packaging equipment, washdown environments

How to Choose the Right Overpressure Gauge for Your Application?

Both gauges provide strong protection against pressure spikes, extend instrument life and reduce the need for external protection devices.

You may prefer the 1209 XRA if you need:

• Superior corrosion resistance
• Standard high accuracy
• A stainless-steel case and wetted system throughout

You may prefer the T6500 XRA if you need:

• A rugged gauge for heavy vibration or outdoor conditions
• Flexibility in dial size and mounting options

Talk to one of our experts today at (855) 737-4714 or fill out our online form to learn more.

Across industries like manufacturing, energy, HVAC, and process control, accurate pressure measurement is critical to maintaining safety, efficiency, and product quality. Over time, even high-quality pressure transducers can experience drift — a gradual deviation between actual and measured pressure caused by vibration, temperature changes, or normal wear.

Calibration restores accuracy by comparing the transducer’s output to a known reference standard and adjusting as needed. But with multiple calibration methods available, the right approach depends on your environment, equipment and accuracy requirements.

As a recognized leader in pressure and temperature instrumentation, Ashcroft addresses this challenge with customers frequently. In this article, you’ll learn why pressure transducer calibration is essential, how zero and span adjustability preserve accuracy over time, the difference between primary and secondary calibration standards, and the lab and field methods that are best suited for both every day and hazardous applications.

Why calibrate a transducer?

Pressure transducers convert applied pressure into an electrical output signal. Over time, those signals can drift away from the true pressure reading due to mechanical stress or environmental factors.

Calibration verifies that the transducer’s output aligns with a known primary or secondary reference standard. If deviations are found, adjustments can be made to bring it back into specification.

According to the American Society of Mechanical Engineers (ASME), the reference instrument used for calibration should be at least four times more accurate than the device being tested. This guideline is often called the 4:1 rule. For example, a transducer rated at ±1% of full-scale accuracy should be calibrated using a standard accurate to ±0.25% or better.

Reasons to Calibrate:

1. It's a new instrument that is not calibrated out of the box
2. It's an instrument that has been repaired or modified
3. The recommended usage or shelf life has elapsed
4. A critical measurement is about to take place or has just complemented
5. Whenever the instrument is exposed to an adverse condition like shock and vibration
6. If observations are questionable
7. When specified by a requirement, QA manual, customer specification or the manufacturer

What is zero and span adjustability in the calibration process?

A key part of any calibration process is knowing what’s actually being adjusted — the zero and span points that define accuracy.

Every pressure transducer has two critical reference points — zero and span:

• Zero offset is the output error at the low-pressure end of the range (or full vacuum for compound ranges)
• Span offset is the output error at the full-pressure end of the range

Over time, repeated pressure cycles, temperature changes, or component aging can cause drift at these endpoints. Zero and span adjustability allows users to correct those shifts, aligning the transducer’s output signal with the true pressure values without sending the unit back to the manufacturer.

Benefits of zero and span adjustability

• Field serviceability: Enables recalibration on-site, minimizing downtime
• Cost efficiency: Reduces the need for external recalibration service or sensor replacement
• Accuracy retention: Maintains reliable performance in demanding applications

However, while zero and span adjustments correct performance at the low and high ends of the range, but not necessarily in between them.

Now that we’ve defined what calibration adjusts, let’s look at how it can be done. Calibration methods generally fall into two categories — laboratory calibration for high accuracy and traceability and field calibration for quick verification and adjustment.

Primary and secondary calibration standards

Every calibration process relies on reference standards that define accuracy. These are classified as primary or secondary:

• Primary standards are the highest accuracy reference devices available. They establish pressure based on fundamental physical principles rather than a comparison. A deadweight tester is the best-known example of a primary pressure standard. Because it generates a known, traceable pressure, it’s used in laboratories to validate other instruments.
• Secondary standards are instruments that have been calibrated against a primary standard. They maintain high accuracy and are used to calibrate working instruments in both laboratory and field settings. Examples include digital test gauges and handheld calibrators.

Understanding how primary and secondary standards relate ensures your calibration process maintains a clear traceability path back to a national standard such as the National Institute of Standards and Technology (NIST), guaranteeing accuracy and compliance in your measurement records.

While calibration standards define the reference for accuracy, the calibration method describes how that reference is applied in practice. The following sections describe these methods in detail — from laboratory precision testing to field and hazardous-area calibration.

In the lab: manual calibration with a deadweight tester

Deadweight testers, like the Aschroft® Deadweight Tester 1305D, is considered the primary standard for pressure calibration and the best approach for high-precision verification. It operates on the fundamental principle that pressure is created by applying a known force over a specific area.

How it’s done:

• Connect the transducer and a reference gauge to the tester
• Apply known weights to generate pressure points across the measurement range
• Compare the transducer’s electrical output (voltage or current) with the reference readings
• Adjust zero and span until both match

This method delivers extremely high accuracy and traceability but requires controlled conditions, making it best suited for laboratory environments or when calibrating master reference instruments.

In the field: method using handheld or digital calibrators

When sending instruments to a lab isn’t practical, technicians can use portable instruments like the Ashcroft® ATE-2 Handheld Calibrator and Ashcroft's Digital Test Gauges to provide a versatile solution in the field for preventive maintenance, quick checks and on-site verification.

How it’s done:

• Connect the transducer and calibrator in a loop with a pressure source
• Apply pressure using a pump or regulator
• Compare the transducer output with the calibrator’s display
• Adjust zero and span either mechanically or through configuration software if the readings differ

This approach allows for regular field verification with good accuracy and minimal downtime — ideal for maintaining performance between lab calibrations.

Calibrating pressure transducers in hazardous areas

In industries such as oil and gas, chemical processing, or paint and coating, calibration often occurs in hazardous environments where explosive gases, vapors, or dusts are present. In these cases, transducers must be certified as explosion-proof (XP), intrinsically safe (IS), or non-incendive (NI) — each offering protection in a different way:

• Explosion-proof (XP): Contains any ignition within the housing
• Intrinsically safe (IS): Limits electrical energy to prevent sparks
• Non-incendive (NI): Restricts energy under normal conditions

Traditional calibration methods that involve opening the housing or adjusting internal screws can’t be performed safely in these environments. To address this, the Ashcroft® E2S Intrinsically Safe Pressure Transducer and E2F Explosion Proof Pressure Transducers incorporate zero and span adjustability designed for hazardous areas.

Magnetic calibration with Ashcroft® pressure transducers
The Ashcroft® E2 Pressure Transducer Series features an external magnetic calibration system that allows users to perform precise zero and span adjustments without opening the housing. These options offer safe, efficient and repeatable field calibration in hazardous or outdoor applications.

How it works:

• The E2G includes an internal magnetic sensor that responds to a calibration magnet tool
• Holding the magnet near marked points on the housing engages calibration mode
• This allows zero and span corrections to be done quickly and safely - Watch video for details
   

Magnetic advantages

• Non-invasive: Preserves explosion-proof integrity and IP66/67 seal
• Fast: Calibration can be completed in minutes
• Safe: No tools or electrical exposure in hazardous areas
• Repeatable: Ensures long-term stability and SIL 3 safety compliance

When calibrating in hazardous zones be sure to only use approved magnetic tools and ensure all portable calibrators or power supplies are rated for the same hazardous area or isolated by barriers. To maintain certification compliance, always follow the manufacturer’s installation and safety documentation.

Regardless of the application, regular calibration ensures pressure transducers deliver consistent, reliable measurements throughout their service life. Understanding zero and span adjustability, along with the role of primary and secondary standards, helps determine the best method for maintaining accuracy. 

Talk to one of our experts today at (855) 737-4714 or fill out our online form to learn more.

When measuring pressure in challenging environments involving extreme temperatures, your instrument must perform accurately and reliably. Temperature exposure can come from many sources, including the process media and the ambient temperature surrounding the sensor. Each affects the transducer differently, but media temperature has the most direct impact because it acts on the sensing diaphragm and internal components. As media temperature rises or falls, it can distort readings, shorten sensor life or even damage components.

With more than 175 years of pressure and temperature measurement expertise, Ashcroft is recognized as an industry authority in helping customers maintain reliable measurement in even the harshest environments.

In this article, you’ll learn how process media temperature can impact pressure transducer performance, what causes output changes and how to minimize errors through proper design and installation. Understanding this information will help ensure you protect your instruments from performance drift or premature failure.

What is media temperature?

Media temperature refers to the temperature of the process fluid or gas that comes into contact with the sensing element of the pressure transducer. It is different from the ambient temperature, which affects the external housing and electronics. Both can influence performance, but media temperature typically has the greatest impact because it directly affects the sensing diaphragm and internal components.

As temperature changes, the materials inside the transducer—metals, adhesives, and fill fluids—expand or contract at different rates. This expansion and contraction can create stress on the sensing element, causing output changes even when pressure remains constant. If the temperature exceeds the transducer’s rated limit, it can permanently alter the properties of these materials and affect long-term performance.

How does temperature compensation work?

Temperature compensation works by using internal electronics to sense the device’s temperature and automatically adjust the measurement signal, reducing temperature-related errors. While this enhances accuracy, it is most effective when the entire pressure transducer remains at a uniform temperature. If parts of the transducer heat up or cool down at different rates—for example, during sudden changes in media temperature—uneven temperatures can cause temporary inaccuracies until the whole device reaches thermal equilibrium.

In applications where temperature changes slowly over several hours or days, the transducer is more likely to reach a stable temperature throughout, allowing compensation features to function optimally. However, in situations where media temperature shifts rapidly but the surrounding environment remains steady, targeted mitigation strategies are needed to address the resulting temperature effects on accuracy and stability.

How does temperature affect the mean time between failure?

Fluctuating or extreme temperatures can significantly impact instrument reliability. Temperature cycling introduces mechanical and electronic stress, while prolonged exposure to high operating temperatures is known to reduce the lifespan of electronic components.

To assess expected device longevity, Mean Time Between Failure (MTBF) calculations are commonly used; as a rule of thumb, MTBF typically decreases by half for every 10 °C increase in operating temperature. To enhance reliability and measurement accuracy, it is essential to implement solutions that bring equipment closer to ambient temperature conditions.

To mitigate the effects of temperature, you need to find a solution to make the equipment closer to ambient temperature, which will help with accuracy and reliability.

How to mitigate temperature effects

To protect your measurement instruments from damage, it’s important to ensure that the media temperature does not exceed the product’s specified operating range, which can happen when the transducer is mounted directly to a process line.

Several measurement instrument accessories are designed to help protect your instruments from this risk, including:

Capillary lines
Accessories like the Ashcroft® 1115 Capillary Line create physical distance between the process and the transducer, allowing you to mount the transducer in an area that is less exposed to extreme temperatures. One end of the capillary attaches to the process, while the other connects to the transducer. This arrangement keeps sensitive components away from potentially harmful process temperatures.

By reducing the amount of process media in the line and increasing the surface area exposed to ambient conditions, capillaries help bring the process media temperature closer to a safe operating range. Even a short length—just a few inches or centimeters—can make a significant difference in restoring media temperature to levels that are safe for the instrument (see Figure 2 below).

Capillaries work well in applications involving gases or liquids that are not expected to have rapid changes in pressure or large amounts of media flow in/out. When flow or rapid changes are expected, there are other solutions to consider.

Diaphragm Seals
Diaphragm seals are used to protect pressure transducers and other instruments when direct process compatibility is needed. They effectively seal and isolate the connection, preventing process media from entering the instrument while still allowing accurate pressure measurement.

It's important to note, however, that diaphragm seals can influence measurement accuracy because additional pressure is required to displace the fill fluid within the seal. This effect on accuracy is more pronounced with seals featuring higher spring rates, fill fluids with greater thermal expansion, and when used on lower-pressure range instruments.

To maintain reliable performance, it is considered best practice to recalibrate the pressure transducer with the diaphragm seal installed at the anticipated operating media temperature.

Steam Siphons
When measuring pressure in steam process lines, special considerations must be taken into account due to the significant energy carried by steam. Traditional accessories, such as extended capillaries, may not adequately reduce temperature because of the continuous movement of steam.

In these scenarios, steam siphons are specifically engineered to protect pressure transducers from elevated steam temperatures. By forming a condensate barrier, steam siphons shield the instrument from direct steam exposure and rapid temperature fluctuations, ensuring accurate measurements and extending the service life of the equipment.

Talk to one of our experts today at (855) 737-4714 or fill out our online form to learn more. 

Pressure gauges are instruments designed to deliver reliable and accurate readings in demanding applications. Yet, even the most durable gauges can lose accuracy or fail prematurely if they aren’t stored correctly. Many issues that appear as calibration drift or pointer error actually begin long before the gauge is installed—during storage and handling.

As a trusted authority in pressure and temperature instrumentation for more than 170 years, Ashcroft has seen how improper storage can shorten the life of an otherwise high-quality gauge. In this article, you’ll learn how to properly store a pressure gauge, how environmental conditions affect performance, and what steps ensure your instruments remain ready for use.

Why is proper storage of your pressure gauge so important?

Pressure gauges depend on sensitive internal parts—like the Bourdon tube, movement, and pointer—to function accurately. When exposed to vibration, dust, moisture, or temperature extremes during storage, these components can degrade or shift out of calibration.

Proper storage helps you:

• Maintain gauge accuracy and calibration integrity
• Prevent corrosion or contamination
• Protect delicate mechanisms from mechanical damage
• Extend the gauge’s service life and reduce premature replacement
• Even if a gauge has never been used, improper storage can compromise its reliability once installed, leading to inaccurate readings or process safety risks.

What environmental conditions can affect a stored pressure gauge?

There are many environmental factors to consider when storing your pressure gauges. Three common conditions that require extra precaution during storage, include:

1. Temperature and humidity
Gauges should be stored in a dry, temperature-controlled environment. Humidity causes corrosion and condensation inside the case, while extreme temperatures can affect internal elasticity and fill fluid stability.

Keep the storage area between 40°F and 85°F (4°C–29°C) and maintain relative humidity below 85%.

If you must store gauges in unconditioned areas, seal them in plastic bags with a moisture-absorbing pack.

2. Dust and contaminants
Dust, debris, and airborne particles can clog the pressure connection or interfere with pointer movement. Store gauges in their original packaging or sealed containers to prevent exposure to contaminants.

3. Vibration and shock
Gauges are sensitive to impact. Place them on a padded, stable surface and avoid stacking heavy items on top. During storage or transport, keep them secure to minimize movement or vibration that could affect calibration.

Together, these environmental factors can gradually compromise a gauge’s performance long before it’s put into operation. By keeping instruments clean, dry, and protected from impact, you help preserve calibration integrity and extend service life—ensuring that each gauge performs as accurately in the field as it did when it left the factory.

Preparing pressure gauges for storage

Packaging plays an essential role in protecting pressure gauges during both shipping and long-term storage. Ashcroft gauges are packaged in durable cartons designed to minimize vibration, moisture exposure, and handling damage.

To maintain protection:

• Keep gauges in their original packaging until installation.
• Ensure protective caps remain on the pressure connections.
• Use foam or molded inserts if the original box isn’t available.
• Store cartons on shelves or pallets—never directly on damp floors.

If gauges will be stored for extended periods, place them in sealed plastic bags with desiccant packs to limit humidity exposure. Also, avoid storing gauges in direct sunlight or near heat sources, as UV exposure and temperature cycling can degrade dial markings and gaskets.

Can storage conditions affect pressure gauge accuracy?

Yes. Even when not in service, gauges can lose calibration if subjected to vibration, temperature variation, or improper storage orientation. Before reinstalling a stored gauge:

• Check that the pointer returns to zero at ambient pressure.
• Inspect the case and connection for corrosion or leaks.
• Verify the lens and fill fluid (if applicable) are clear and intact.
• Recalibrate gauges that have been stored for more than one year or under unknown conditions.

Most importantly, consider the calibration of your gauges throughout their storage period. Even when unused, gauges can drift over time due to material relaxation or environmental exposure. The frequency of recalibration depends on your process requirements, but it should be performed on a regular schedule. 

How do you store liquid-filled gauges?

Liquid-filled gauges are often used to dampen vibration and protect the internal mechanism, but the fill fluid (usually glycerin or silicone) is sensitive to temperature and position.

To store them properly:

• Keep them upright in a shaded, temperature-stable location.
• Avoid freezing temperatures, which can cause the fill fluid to expand and damage the lens.
• Do not expose to direct sunlight or heat sources.
• Wipe the case and window clean before packaging.

The most common fill fluids are glycerin, silicone, and halocarbon, but others may be used depending on the application. Each fluid type reacts differently to temperature changes—so understanding those limits is essential. For example, glycerin should never be exposed to temperatures below 0°F (-18°C), as it can freeze and damage the instrument.

If the fluid becomes cloudy or discolored, the gauge should be inspected before reuse—this can indicate contamination or seal degradation.

What is the best way to handle pressure gauges during storage transit?

Proper handling prevents mechanical damage that might not be visible until installation. Follow these guidelines:

• Handle gauges individually—never carry them by the connection threads.
• Avoid touching the dial face or pointer.
• Use protective caps on connections at all times.
• Store upright on shelves or racks, not loosely in bins.
• During shipment, use foam-lined or anti-vibration packaging to protect delicate internal components.

Talk to one of our experts today at (855) 737-4714 or fill out our online form to learn more. 

Pressure gauges can be found in virtually every industry. Depending on your application, these instruments play an important role in measuring the air, gas or liquid pressure in your system to keep it running safely and smoothly. However, for optimum efficiency, you will need to make sure the pressure range you choose for your gauge aligns with your application requirements and a few other factors.

Ashcroft has been in the pressure gauge business for more than a century and a half, so following the guidelines in this article can save you time and give you confidence in your purchasing decision. Read on to learn about the factors to consider when choosing the pressure range for your gauge. Then, when you are done, we will share additional information about pressure gauge selection that you can use as a reference.

Follow ASME's best practices for operating pressure.

The first step in selecting a pressure gauge range is to understand the operating pressures of your process. Ashcroft follows ASME B40.100 standards, which recommend the following:

• Operating pressure should be 25% to 75% of scale, and the gauge range should be twice the operating pressure.
• Ideally, the mid-scale on your dial should be around 12 o’clock, or the mid-scale of the full-scale gauge span.
• If pulsation is present, the maximum operating gauge pressure should not exceed 50% of the full-scale range.
   

Know the maximum design pressure for your application.

After operating pressure, the next thing you need to confirm is the design pressure. The design pressure is the maximum pressure that your gauge will experience during your application at a given moment in time (not sustained). There can be a surge of pressure when the machine turns on, or surges or pressure spikes can happen at other times during the application.

Pressure gauges can handle 130% to 150% of the range, depending on the range, but if the pressure goes beyond that you will need to get a gauge with a higher range or protect the gauge from inaccuracy issues or possibly overpressure that can cause gauge failure. Both factors are safety issues that should not be ignored. 

A pressure limiting valve (PLV) can help protect the gauge from overpressure by shutting off the pressure going into the gauge. Consider this accessory when process pressure can at times exceed 130% to 150% of the range.

The PLV is usually set at the full-scale range of the gauge. When the pressure reaches the setpoint of the PLV, pressure into the gauge is shut off, protecting the gauge from overpressure. It will also contain the process media so nothing dangerous leaks out into the environment.

Other gauge factors to consider when choosing a pressure range. 

After determining the operating and design pressure of your application, you will need to look at the other factors that can influence the final range you select, including:

Dial Sizes and Features
All pressure gauges have a variety of dial size options and features to consider. Depending on the range you need, dial sizes typically range from 1 ¼ in. to 16 in. Gauge size and readability are very important considerations. The larger the dial, the easier it will be for the operator to read. You can narrow down your options by asking yourself:

• Do I need to read the gauge from a distance?
• How far away is the gauge from the operator?

Dial features on the other hand also consider numeral type, major graduations and minor graduations.  

Minor graduations can be difficult to read if they’re too close together, so consider the readability of these smaller graduations when selecting the best dial size.

Other considerations:

• Pointer width. This cannot be greater than the width of the dial graduations and may be a limiting factor when determining how many graduations are available with corresponding dial sizes.
• Space restrictions.  If there is not a lot of space where the gauge will be installed, you may also be limited in your dial size selection.
• Dial arc. Typically, the dial arc of a gauge is 270 degrees in accordance with ASME B40.100 guidelines. However, some dial arcs are less than 270 degrees.
• Low-light conditions. If your gauge needs to be read in dimly lit areas, using a retroreflective dial material like the Ashcroft Duravis™ gauge dial is a good option. The retroreflective material is the same material used on stop signs. Unlike a reflective material that disperses light in different directions, Duravis™ material reflects light back to the light source, making readability easier. See Figure 2 below.
• Customization. Ashcroft offers a variety of printing options for your dials. We can add your logo, use your brand colors, create special dial markings, add color zones and more to accommodate and personalize the gauge for the application.  Figure 3 below is an example of a colored zone dial using green to indicate a safe zone, yellow to indicate caution and red for danger.  

Scale Options
When it comes to gauge scales, you will want to confirm the following which can also affect the range:

• Which unit of measure is required? In the U.S., a pound of force per square inch or PSI is common. Other popular units of measure include kPa, kg/cm2 and bar.
• How many units of measure are needed? If your application requires a dial with multiple units of measure, you can select a single, dual, triple or quadruple scale option. Regardless of the one you choose the dominant scale that will be read most will be the inner scale where the numerals and graduations are larger than the outer scale.
• Whether you need a refrigerant scale. Refrigerant scales like ammonia or refrigerants R11, R12 and 134A can measure both pressure and a corresponding temperature scale. Refrigerant scales that measure both pressure and vacuum are common. Typical units of measure are inches of mercury or millimeters of mercury. When there is a need to measure both pressure and vacuum, a compound scale is available (see Figures 4 and 5 below).

Accuracy considerations
Generally speaking, the better the accuracy of the gauge, the more graduations are required. So, if your application requires ±0.5% accuracy or better, a dial size less than 100 mm is not recommended. That’s because the number of required graduations can make the gauge difficult to read.

Minor dial graduations generally do not exceed twice the accuracy of the gauge. As an example, a 100 psi range gauge with a required accuracy of ±0.5% will have minor graduations of 1 psi (refer to Figure 1).

In situations where you require a gauge with better accuracy, this usually means more graduations on your dial. In these cases, consider getting a dial that’s a larger size to accommodate the measurement increments.

Talk to one of our experts today at (855) 737-4714 or fill out our online form to learn more. 

No matter what industry you work in, diaphragm seals (also referred to as isolators) and welded assemblies are used to protect your pressure and temperature instrumentation from corrosive process media.

After decades of making quality pressure and temperature gauges and sensors to help keep processes performing reliably and efficiently, Ashcroft has seen just about every scenario where something can go wrong. One reason we like to share our expertise is to help people like you who may be experiencing a similar issue that we can help solve.

In this article, you will learn what a welded diaphragm seal assembly is and how it is used to help mitigate the damaging effects of high temperature, pulsation and vibration endured by your instruments. You will also see how these assemblies can ensure reliable and accurate pressure readings of your process.

When you are done, you will find links to additional resources that can help you learn more about related topics.

What is a Welded Instrument Assembly?

Simply put, a welded instrument assembly consists of a mechanical measurement instrument like a pressure gauge and an accessory welded together to provide the specific protection you need.  Different conditions and product specifications call for different accessory assemblies. For example:

For corrosion and clogging protection.

• A diaphragm seal/isolator.  Protects the gauge sensor from corrosive process media and prevents clogging of the instrument from a dirty process.

Figure 1. Ashcroft®  

For pulsation protection. 

• A pulsation dampener. Protects measuring instruments from sudden increases and fluctuations of pressure.

Figure 2. Ashcroft® Pulsation Dampener.

For elevated temperature protection.

• A finned siphon. The reduced orifice decreases the volume of the process medium in the siphon allowing efficient heat transfer between the medium and the siphon. 

Figure 3. Ashcroft® Finned Siphon.

• MicroTube™and Mini MicroTube Siphon. The reduced internal volume of these accessories allows for superior temperature dissipation. 

Figure 4. Ashcroft® MicroTube™ and Mini MicroTube™ Siphon.

• A capillary line. This accessory prevents direct contact between the gauge and the installation point to protect it from elevated temperatures or pressure spikes.

Figure 5. Ashcroft® 1115 Capillary Line.

Instruments attached directly to seals can be welded, and assemblies with some accessories can be welded at each connection. However, there are some exceptions. Accessories like snubbers that help protect gauges from pulsation issues, and valves that help with isolation valves cannot be welded since they contain elastomers that will be compromised with the elevated weld temperature.

Figure 6. A Welded Instrument Assembly Example.

Why material compatibility is important in welded assemblies. 

Materials that will be welded together must be compatible. For example, 316 Stainless steel cannot be welded to Monel. If the materials are not compatible, the instrument can be compromised and become ineffective. The good news is there are many material options available for the wetted portion of a diaphragm seal to ensure compatibility with the process media.

How instrument accuracy is affected
Generally, an accessory attached to a gauge does not change the accuracy of the gauge. However, attaching a diaphragm seal/isolator to a gauge can typically reduce the gauge accuracy by ± 0.5% of span.

When it is necessary to weld a gauge to a diaphragm, Ashcroft confirms appropriate assembly accuracy tolerance after the assembly is welded, filled and calibrated. For example, an Ashcroft® 1279 Pressure Gauge with an accuracy of
± 0.5% when it is attached to a diaphragm seal, will usually have an accuracy of ±1% of span.

If the same Pressure Gauge is welded to a MicroTube™ Siphon and a Threaded Diaphragm Seal and then filled and calibrated, the typical gauge accuracy of the assembly will also be ± 1% of span. So, additional accuracy occurs only when a diaphragm seal is added to the assembly.

Why Use a Welded Instrument Assembly?

More and more customers are seeing the value of a welded instrument assembly. A welded instrument assembly can be used in any application and is good for all industries.

Prevents accidental tampering or disassembly. A welded assembly is tamperproof and prevents a diaphragm seal from being detached from the gauge. This is important because removing the gauge from the seal breaches the assembly's system integrity and will render the gauge inoperable.

The tamperproof welded design also prevents an important accessory from being removed. For example, if the process temperature is 800 °F/427 °C, design engineers may specify that a siphon needs to be attached to the assembly to dissipate process temperature and protect the gauge. If the siphon is removed from an assembly that is not welded, the gauge will lose its integrity and not give an accurate process pressure reading.

Primary benefits to welded assemblies. 
A welded assembly provides peace of mind that the components of the assembly won’t be removed. Here are a few other reasons why a welded assembly can benefit you.
 

Note: If at some point welded components need to be replaced, replacement of the complete assembly would be required. Replacing individual instruments and accessories of a welded assembly is not an option. Breaking any welded connection of an assembly would result in damage to the instruments and accessories.

Talk to one of our experts today at (855) 737-4714 or fill out our online form to learn more. 

Selecting the correct electrical connection for a pressure transducer helps ensure your equipment continues to operate effectively, even when affected by vibration, moisture, dust, or temperature extremes that can compromise performance. From off-road equipment to process automation systems, choosing the wrong connector can lead to signal loss, premature failure, or even safety risks.

As a recognized authority in pressure and temperature instrumentation, Ashcroft has extensive experience helping engineers and operators protect their systems in the harshest conditions. Read this article to learn the factors to consider when selecting an electrical connector for a transducer:

• Why connector selection directly affects sensor reliability and longevity
• What environmental conditions should guide your connector choice?
• What installation and wiring factors should you consider?

Why is selecting the right electrical connection so important for pressure transducers?

Electrical connections do more than deliver power and transmit output signals—they provide essential protection against environmental hazards. A weak or poorly matched connector can cause intermittent readings, corrosion, or total sensor failure.

For example, in mobile hydraulic systems or compressors, connectors endure high vibration and thermal cycling. Over time, these stresses can loosen fittings or compromise seals, allowing moisture or debris to enter. The result is drift, erratic output, or short circuits. Reliable connections ensure:

• Signal integrity: Stable voltage or current output without dropouts
• Environmental protection: Proper sealing against contaminants like dust and oil
• Serviceability: Ease of installation, maintenance, and replacement
• Safety: Electrical isolation in hazardous locations where explosive gases or dust may be present

Ultimately, the right connector enhances the durability and reliability of the pressure transducer throughout its service life. When choosing an electrical connector that would function best in your application, be it indoors or outdoors and exposed to the elements, there are many factors to keep in mind.

What environmental conditions should guide your connector choice?

The environment in which a transducer operates determines the level of protection required. For instance, will your pressure transducer be installed outside, or will it be regularly exposed to moisture, dust or sunlight?

Both the National Electrical Manufacturers Association (NEMA) and the International Electrotechnical Commission have established standards, which specify how effectively a transducer's enclosure keeps the user safe from electrical hazards and prevents the entry of solids, liquids and other contaminants into the instrument.

NEMA rating examples

There are many different NEMA ratings that define how well an enclosure performs in different environmental conditions, including:

• NEMA 4 enclosures provide a degree of protection to personnel against incidental contact with the enclosed equipment. It protects against windblown dust and rain, splashing water and hose-directed water, making them ideal for outdoor use.
• NEMA 4X offers similar protection but with added resistance to corrosion, which is common in food, beverage or chemical processing environments.
• NEMA 7 enclosures are designed to contain an internal explosion without causing an external hazard.
• NEMA 9 enclosures are designed to prevent the ignition of combustible dust for use in hazardous areas.

Most Ashcroft pressure sensors predominately fall into the NEMA 4, NEMA 4X, NEMA 7/9 category ratings. For example, the Ashcroft® E2G Pressure Transducer has a NEMA 4X rating, so it offers the same protection as the NEMA 4, with the addition of corrosion resistance.
 

IP rating examples

In a previous article, we explained that ingress protection (IP) ratings typically consist of two numbers. The first indicates how well the instrument protects against solids (like dust). Solid ratings go from a low of 1 up to the highest rating of 6. The second number indicates how well the enclosure or sensor protects against liquids. See Figure 1 for full list. 

Talk to one of our experts today at (855) 737-4714 or fill out our online form to learn more. 

In industries where temperature extremes, vibration, or hazardous process environments are part of daily operations, accurate and reliable temperature measurement becomes a serious challenge. In these environments, operators need instruments that deliver accurate readings from a safe distance, reducing the need to approach hazardous areas.

Gas-actuated thermometers are an effective solution for these applications. Their robust design, wide measurement range, large dial size and remote mounting capabilities make them ideal when both safety and accuracy are priorities.

As a global authority in pressure and temperature instrumentation, Ashcroft has helped manufacturers and process operators improve reliability and reduce downtime for more than a century. In this article, you’ll learn:

• How gas-actuated thermometers work
• When and where they are most effective
• Why remote mounting and thermowell selection matter
• Which design options can extend instrument life in extreme conditions
   

When are gas-actuated thermometers used?

Gas-actuated thermometers are best used when applications involve:

• Extreme temperature ranges. Common in refineries and power generation plants, where process media can swing from cryogenic to several hundred degrees and standard thermometers cannot operate reliably.
• Vibration or shock. Found in offshore oil rigs or pulp and paper mills, where rotating machinery or pumps can cause continuous vibration. The “movementless” Bourdon tube design helps minimize wear and eliminates pointer flutter.
• Remote monitoring requirements. Typical in chemical and petrochemical facilities, where operators must read temperatures from safe control areas away from high-pressure or corrosive processes. Capillary lengths up to 80 feet or 100 meters allow operators to mount the dial in a safe, accessible location while the sensing bulb is near the process source.
• Hazardous or confined environments. Seen in food, beverage, and pharmaceutical manufacturing, where sanitary requirements or confined equipment layouts make remote mounting safer and more practical. Remote mounting lets personnel take readings from control panels or safe areas, away from heat, obstructions, or caustic media.
• Outdoor or wide-area systems. This can include water and wastewater treatment sites, where thermometers may need to be installed far from monitoring stations.
   

How do gas-actuated thermometers work?

Gas-actuated thermometers use a Bourdon tube system filled with an inert gas to sense and indicate temperature changes. As the temperature rises, the gas expands within the sealed system, creating pressure inside the Bourdon tube that moves the pointer across a calibrated scale.

In remote-mount designs, the gas pressure travels through a capillary line that connects the sensing bulb to the dial, allowing the indicator to be installed at a safe or more accessible distance.

Because the system is completely sealed and filled with gas, it delivers fast response, linear accuracy and stable readings across a wide range—from approximately –320 °F to 1,200 °F (–200 °C to 650 °C).

This design makes gas-actuated thermometers ideal for both direct-mount installations and remote applications where the sensing bulb and dial must be separated for visibility, accessibility, or operator safety.

Electric contact switches can be added to the thermometer for process alarm or control.

Why is remote mounting important for gas-actuated thermometers?

Remote-mounted thermometers separate the dial indicator from the temperature-sensing bulb, connected by a gas-filled capillary line. This configuration helps:

• Reduce vibration damage by isolating the sensitive indicator from pumps, compressors, or piping.
• Protect operators from hot or hazardous process zones.
• Simplify readings by allowing installation on panels or easily visible control stations.

Ashcroft’s Duratemp® 600A and 600H-45 Gas-Actuated Thermometers, for example, offer bendable extension bulbs with adjustable union connections that can be freely positioned for the best insertion depth. The armored capillary provides added mechanical protection.

How do bulb and thermowell configurations affect performance?

The bulb acts as the sensing element, while the thermowell shields the bulb from pressure, corrosion, and velocity effects. Two common bulb types are:

• Plain bulbs. Best for air or liquid measurement in open tanks or low-pressure environments.
• Union-connected bulbs. Threaded fittings that secure the bulb into a thermowell, making them ideal for pressurized or corrosive processes

Using a thermowell not only extends the thermometer’s service life but also enables instrument interchange or recalibration without process shutdown—a best practice across high-reliability industries.

Talk to one of our experts today at (855) 737-4714 or fill out our online form to learn more.