Blog Pressure Switches

UL-Rated 703-U/UJ Pressure Switches Achieve Long Life in Explosive Environments

Gaseous or liquid fluid systems in hazardous locations demand the toughest pressure switches. These components must incorporate heavy-duty designs that offer exceptional accuracy despite harsh environmental conditions. They must also carry the right safety ratings, guaranteeing reliable operation in applications like offshore exploration and petrochemical processing. 

Our 703-U and 703-UJ Series of UL-rated, explosion-proof pressure switches fit the bill. These heavy-duty components feature a corrosion-resistant stainless steel construction and UL ratings for hazardous locations, including:

  • Class 1: Division 1, Groups A, B, C, D
  • Class 2: Division 1, Groups E, F, G

With high overpressure capabilities and a NEMA Type 7 explosion-proof rating, the 703-U/UJ Series integrate a rugged piston design, which enables these switches to withstand high pressure spikes, shock and vibration. The 703-U Series features factory-set fixed pressure, while the 703-UJ features field-adjustable pressure. Designed for easy field adjustment, the 703-UJ also incorporates a tamper-resistant locking mechanism to maintain set point integrity.

Additional features and specifications of the 703-U/UJ Series include:

  • Pressure range: 6 to 5,000 PSI
  • Temperature range: -40 to +180°F (703-U Series)
  • Pressure connection: 1/4-inch–18 NPT (male) and 1/2-inch–14 NPT (male)
  • Single pole double throw (SPDT) option
  • Double pole double throw (DPDT) option
  • 1/2-inch NPT electrical connection with five full threads for conduit engagement
  • Factory-sealed lead wires — Type UL 1015 AWG #18, 24 inches long
  • Hydraulic and electric modules AISI 316 stainless steel

Thanks to their durable construction, 703-U/UJ pressure switches boast exceptional accuracy and repeatability — even in explosive environments. And, they guarantee a long service life; the units’ snap-action electrical switch is tested to 1 million cycles. For these reasons, the 703-U and 703-UJ Series are ideal for applications like off-shore exploration, petrochemical processing, oil and gas pipelines, control panels and industrial OEM equipment.

To learn more, please visit our product page.

Blog Pressure Switches

Pressure Switches Combine Accuracy and Reliability for Oil and Gas Operations

Pressure switches for oil and gas facilities have to meet a set of challenging requirements. Not only should the switch provide exceptional accuracy and reliability, but it also must be suitable for use in hazardous locations—and carry the safety ratings to prove it.

Our Model 703-U and 703-UJ explosion-proof pressure switches with piston actuation combine uncompromising safety and protection with the accurate, reliable switching that mission-critical operations demand. The switches are listed for use in hazardous locations as specified by UL Class 1 Division 1, Groups A, B, C and D and Class 2 Groups E, F and G. And, they are NEMA Type 7 Rated for explosion protection.

They also feature a rugged, piston-actuation design to ensure optimal reliability. That’s because switches with a piston-based design are particularly able to manage high pressure spikes, leaks, vibration, shock and thermal extremes without losing accuracy or failing prematurely.

The pressure switches provide two options for safe and secure control of set points:

  • Model 703-UJ has been designed for easy field adjustment, letting users adjust pressure levels as conditions change. Once the setting is in place, 703-UJ’s tamper-resistant locking mechanism keeps it secure.
  • Model 703-U, which has factory-set pressure.

Along with its piston design, the highly rugged Model 703-U/UJ features:

  • NEMA Type 7 Rating for explosion protection.
  • 316 stainless steel construction to resist corrosion.
  • High overpressure capability.
  • Pressure handling up to 5000 psig.
  • Wide operating temperature range of -40°F to 180°F
  • Long lifetime — the snap-action switch has been tested to 1 million cycles.

Model 703U/UJ pressure switches are suitable for a wide range of upstream and downstream oil and gas operations such as offshore exploration, petrochemical processing and oil and gas pipelines. Additional applications include industrial OEM equipment and control panels.

To learn more about pressure switches for harsh environments, download our white paper.

Blog Pressure Switches

New Paper Explores How Pressure Switch Customizations Overcome Design Challenges

Download The White Paper

Pressure switches are often considered commodity items. But for many mission-critical or demanding applications—including aerospace, pharmaceuticals and chemical processing—your switch may require a custom mechanical design or electrical features that go beyond what commercial off-the-shelf switches can offer. With a little extra engineering, you can boost the performance of your switch and even overcome challenges your pressure system may be experiencing as a result of its operating environment.

In a new white paper, we explore some recent applications that demonstrate how custom-engineering our pressure switches has improved the functionality of the switch—as well as the reliability of the overall system.

Blog Custom Pressure Switches Pressure Switches Pressure Transducers

Flush-Mount Pressure Switches—And Transducers Too

Food, pharmaceutical and chemical processes often use tubular equipment to mix, transport or store materials. In these applications, it’s a good idea to keep any internal switches or sensors from protruding too far into the tube—where they can create a toehold for material buildup or impede flow. That’s where our newest pressure switch design comes into play.

This custom switch’s sensing element has been designed and manufactured to match the interior curvature of a specific food processing machine. The only part that protrudes into the flow within the machine is a low-profile, seamless seal that provides no place for materials to hang up during production.

While this particular flush-mount switch was designed for a specific use, the same approach can be applied to a wide variety of processing machines. We can alter the design of the switch for tubular structures with internal diameters as small as three inches.

We’ve also created a similar design for flush-mount pressure transducers.

Click here to learn more about our custom pressure switch capabilities.

Blog Custom Pressure Switches Pressure Switches

Thermal Lockout for Hermetic Pressure Switches

In hydraulic systems, cold start-ups often cause pressure switching errors that disappear once the system reaches its normal operating temperature. The culprit behind these false high pressure signals is increased fluid viscosity, which temporarily increases the differential pressure across the diaphragm or pressure sensing device. A thermal lockout mechanism based on a snap-acting, temperature-sensitive bimetallic disc can prevent this problem.

Check out our infographic to see how it works.

Blog Custom Pressure Switches Pressure Switches

Off-Road Vehicle Sees Success In Pressure Switch Signal Delay


If your hydraulic systems suffer from pressure spikes, your pressure switches may not work as expected. The spikes can trigger the switch prematurely, even though continuous pressures remain below the set point. The result is a hard-to-control hydraulic system plagued by false switching signals.

Fortunately, there’s a simple solution to these spike-induced switching errors: Just add a time delay to the switch. That’s exactly what we did in a recent application.

Off-Road Vehicle Experiences Pressure Transients. In an off-road vehicle, a pressure switch was used as part of a hydraulic monitoring system, which was designed to trigger a warning light in the cabin if it experienced sustained excess pressure. But driving over rough terrain was causing unintended pressure spikes, causing the annunciator light in the crew compartment to constantly switch on and off.

Our engineers incorporated a PC board into the pressure switch that was programmed to delay signal output based on certain adjustable parameters, including the amount of time—down to the millisecond—and whether the signal occurred on the rising or falling pressure. In this case, engineers set the time delay at 3.2 seconds. As a result, the warning light remained off unless a pressure change lasted longer than that.

Pressure Switches For Tough Environments. In addition to integrating time delays, these pressure switches had to be ruggedized for use in an off-road application and are designed to withstand pressure spikes, leaks, temperature extremes, moisture, chemical exposure, vibration and shock loads. These ruggedized features include:

  • Proof pressures up to 12,000 psig
  • Maximum operating pressures up to 7,500 psig
  • Wide temperature range of -40 to 250°F
  • High overpressure capability
  • High shock and vibration survivability
  • Snap-action electrical switch tested to 1 million cycles
  • IP67 compliance

To learn more about pressure switch design, download our latest white paper.

Blog Pressure Switches

New Diaphragm-Operated Pressure Switches For Tough Environments


With the release of our 745 and 785 Ruggedized Pressure Switches, we’re expanding our product line to help you better address low pressure applications that require high-sensitivity.

745 Pressure Switch. Our diaphragm-operated Model 745 Fixed Setting Pressure Switch is designed for low-pressure operations that require a compact form factor and high degree of sensitivity. Typical application examples include off-road or industrial OEM equipment, train braking systems, compactors, compressors and fuel systems.

785 Pressure Switch. Equipped with either a 2- or 3-pin Deutsch connector, this miniature, diaphragm-operated pressure switch is designed for high-sensitivity, low-pressure applications. Like the 745 model, this switch is IP67-compliant and has a NEMA Type 4 rating for a high degree of protection in rugged indoor and outdoor applications.

Both pressure switches are built to thrive in tough environments, providing pressures between 7 and 160 PSIG. They can withstand oil, fuel, water, dust, vibration and shock and feature a wide temperature range of -40 to +250°F.

Depending on the application, you can choose from several standard electrical and pressure port configurations. You can also customize your model with special items, including wire, cable, seal materials and weather-proof connectors.

For more information on the 745 Series, download the 745 Series Datasheet.

For more information on the 785 Series, download the 785 Series Datasheet.

Blog Pressure Switches

New 2-Pin Deutsch Pressure Switch For Tough Environments

784 2-Pin Deutsch

Our 784 Series of ruggedized pressure switches can now address more applications than ever, thanks to the addition of a compact 2-pin Deutsch option. Other than the change in connector, the pressure switch offers all the same performance characteristics as the original 3-pin Deutsch version.

IP67-Compliant Pressure Switch. Whether 2- or 3-pin, the 784 pressure switch complies with IP67 standards for maximum environmental protection. This model thrives in tough environments containing oil, fuel, water, dust, vibration or shock.

With a temperature range from -40 to 250°F, the 784 pressure switch comes with a piston, fixed pressure, integral pressure port snubbing and an 8 to 6,000 psig range. Some common applications include:

  • Off-road equipment
  • Industrial OEM equipment
  • Train braking systems
  • Packaging equipment
  • Compactors
  • Compressors

Other Features. This customizable pressure switch also features a snap-action electrical switch tested to one million cycles, gold contact switches for dry circuit applications, high overpressure capabilities and custom configurations. In addition, this model meets UL safety standards and NEMA type 4 outdoor applications and instances where water is present.

You can learn more about our design approach to ruggedized sensors in our latest white paper.

Blog Pressure Switches

Video: Ruggedized Switches Withstand Pressure Spikes

Ruggedized pressure switches have a stable switching response and a long lifecycle in the face of temperature extremes, moisture, chemicals, vibration, shock and pressure spikes—the biggest threat of all. Our high quality switches have a number of design features that help withstand these spikes. Check out this video now.

Blog Pressure Switches

How To Make Pressure Switches That Last

Simple design principles for harsh operating conditions

Pressure Switch White Paper

Ruggedized pressure switches play a critical role in failure-intolerant applications. At Sigma-Netics, we define rugged as a stable switching response and long lifecycle in the face of seven failure modes—pressure spikes, leaks, temperature extremes, moisture, chemical exposure, vibration and shock loads.

Switches that can withstand these life-ending failure modes have three design principles in common. They tend to have a piston rather than diaphragm design. They have carefully designed pressure management features and seals. And they use materials and construction methods that mitigate chemical and moisture exposures, as well as thermal expansion mismatches.

In our latest white paper, we’ll take a closer look at some design principles of ruggedized pressure switches.

Download the white paper.