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Learn About Our ProControl Proportional Solenoid Valves

Humphrey ProControl Proportional Solenoid Valves offer a wide variety of pressure opportunities for pneumatic applications. These proportional solenoid valves deliver variable control of compressed air or inert gases based on the corresponding input current to the coil.

Types of Proportional Solenoid Valves

Humphrey offers five different types of flow capacity:

  • Mini PV3 and PV10 solenoid valves: These valves offer precise control in confined spaces, cost-effectively. They deliver 0-32 and 0-75 LPM, respectively.
  • PC30 solenoid valves: Mid-size valves with additional flow capacity ranging from 0-225 LPM.
  • Servoid series: These valves are extremely precise and are excellent for various low-pressure settings. They deliver 0-200 LPM.
  • Balanced servoid: Stable performance regardless of upstream pressure changes. This solenoid valve is the industry standard for biomedical critical care patient ventilators.

Control Output Flow Options

Proportional solenoid valves can be used in medical, analytical, instrumentation, test, measurement, factory automation and process control applications.

These valves come with three types of flow options:

  • Selectable: Delivers unique output flow within each cycle.
  • Incremental: Adjusts flow at a predetermined amount within each cycle.
  • Dynamic: Responds continuously to downstream demands.

Proportional Valve Driver

Proportional valve drivers are intended for valves that run on one amp or less, regardless of the valve manufacturer. You can conveniently test, evaluate and use proportional valves with a proportional valve driver in real-time.

Check out our video breakdown for more information. Contact us to learn more about our products.

Breaking Down Proportional Solenoid Valves

Humphrey ProControl™ Proportional Solenoid Valves are an excellent option for pneumatic applications that require variable or controlled valve output flow.

Proportional Solenoid Valves - How They Work

Proportional valves are small two-port, normally closed, direct-acting solenoid valves. They respond precisely to the amount of input current applied to its solenoid. From a stabilized upstream pressure source, customers can expect precise and consistent variable output flow performance for millions of cycles. Output flow adjusts precisely to minor changes in input current.

Proportional valves can enhance pneumatic system performance with soft starts, precision stops, and reduced shock during operation. In closed-loop systems, proportional valves will deliver precise flow control and instantaneous response, even with minute adjustments from input sensors.

The ProControl™ Offering

Today, Humphrey offers three standard valve models and two customizable valve platforms from our Engineered Solutions group. Standard models:

Modifications to standard valves are possible and welcomed. Humphrey can optimize valve performance with an understanding of OEM customer requirements. Contact

The ProControl™ Servoid Series are tailored to specific customer requirements. Featuring very high flow from a low supply pressure source, the Servoid Series can deliver extremely precise and linear output flow with low hysteresis and high-resolution characteristics.

Proportional Solenoid Valve Drivers

Most OEM customers drive proportional valves from their onboard PCB. For others, Valve Drivers are available and are used to take input signals sourced from sensors and deliver appropriate output current to operate the solenoid. Customers use drivers to test, evaluate and use proportional valves on benchtops or in proportional valve projects. Humphrey offers it’s driver with the ProControl™ PCD.

Advantages of Proportional Solenoid Valves

  • Consistent operation without voltage changes
  • Tight seal at rest
  • Low hysteresis
  • Low power consumption
  • Excellent resolution
  • Compact construction

Check out our video breakdown for more information. Contact us to learn more about our products.

Choosing the Right Solenoid Valve for Your Application

There are plenty of variables to consider when selecting a solenoid valve for your fluid control application. Let’s take a look at some of the factors that come into play, and we’ll help narrow your search.

What does the solenoid valve need to accomplish?

Always begin with the valve “need”. What will the solenoid valve do in the application, both in the unactuated, at-rest state, and the actuated, coil-energized, state?  Examples:

  • Control an air cylinder (4-way valve)
  • Start or stop flow only (2-way)
  • Pilot a process valve (3-way)
  • Deliver variable flow (proportional) 

Determine what you need to do and what the timing requirements are. 

What media will the solenoid valve manage?

Your system’s pressurized fluid, whether gas or liquid, is another component to consider when determining the right valve for your application. Secondly, determine the expected minimum & maximum system pressure. It’s essential to find a valve design composition that will perform over an expected cycle life.  

The media’s chemical properties and temperature will dictate the valve’s compatibility. Incompatible valve materials will react to the media, degrade and fail prematurely. Degradation can be gradual, reducing cycle life, and requiring increased preventative maintenance or unexpected repairs.

Will there be more than one media for the application? Consider things like cleaning/flushing fluids, or the possibility of poor or water-ladened compressed air. Always plan for the most challenging media.

What size solenoid valve does the application require?

Properly sizing the flow capacity of the valve is next. Many manufacturers publish a flow rating (LPM, CFM, GPM) at the valve’s maximum pressure specification. Selecting an insufficiently sized valve will degrade system performance, or extend cycle times. It’s crucial to select a valve that can exceed the flow rate of your application, and when a minimum system pressure may exist.  Manufacturers usually provide an industry-accepted flow coefficient (Cv, Kv) that can be used to compare valve brands.

What operating conditions will the solenoid valve face?

Not all solenoid valves are used with clean dry compressed air, controlled precisely to 50 psig and within air conditioned, pristine work environments. Consider more than the most ideal conditions, and specify the valve around those parameters. This includes pressure fluctuations, quality of the media, temperature extremes and work environments.

Consider valve cycle rates and energized times to be expected of the valve, as performance and life of some brands can be affected. And finally, all valves can leak (extremely small amounts) of the media some brands more than others particularly as the valve wears over time. Take reasonable precautions and anticipate valve leakage.

A reliable valve manufacturing partner will help you find the right solenoid valve for any application. Call 800-477-8707 or contact Humphrey Products online, and we’ll get you started.

Basic Pneumatics - Pressure Control and Flow Control

Pressure control is the control of a fluid’s force within a vessel. It is transmitted equally in all directions. Think of your automobile’s tire pressure. When the pressure in all four tires is set properly, collectively they exert enough force (power) within, to safely support your automobile.

Flow control is controlling the movement of pressure between two vessels, and it moves from the vessel with greater pressure. When tire pressure is too high or too low, the tire valve is opened to release pressure from the tire “flowing” to the atmosphere or to receive a greater pressure “flowing” from the air compressor. Of course, a larger opening in the valve (or sadly, a tire blow-out) will flow the higher pressure quickly. 

Today, electronic sensor technology exists such that pressure and flow can be changed dynamically, in a close-looped microprocessor-based system. A simple example is today’s service station tire pump. Program your desired tire pressure and the pump shuts off when it senses 36 pounds of tire pressure.

Flow Control Valves

All valves control flow. The industry term Flow Control Valve refers to its ability to vary the flow of a fixed pressure to its output side. There are manually controlled and current (amperage) controlled valve types.

Manual Flow Control Valves usually have a knurled adjustment knob or throttle. Once the desired flow is set, these valves remain in that flow setting until further adjusted. 

Flow control valves operated by current are commonly referred to as proportional valves. As amperage is applied or varied to its solenoid operator, the output flow of the valve varies accordingly. 

The primary advantage of these “proportional valves” is their ability to be used with a microprocessor-based programmable controller, particularly in closed-loop systems. In these systems, downstream sensors continuously provide feedback to the controller to change (or not) the current to the valve’s solenoid operator.

Other names for flow control valves include needle valves, proportional valves, and meter out valves.

Pressure Control Valves

Pressure Control Valves are commonly called pressure regulators and come in manual and electronic models, similar to flow control valves. Pressure regulators are designed to respond and maintain a controlled downstream pressure setting when a pressure loss or surge occurs. Each pressure regulator has a restriction, load and reference element to respond to pressure and maintain the desired output.

They are only used in closed-loop systems since they require downstream feedback to maintain a set pressure. Pressure Regulators are offered with either piston or diaphragm type valves. Piston types are better suited to rugged applications that require some accuracy and durability, while diaphragms provide precision control.

Contact Humphrey Products online or call 800-477-8707 to learn more about our customizable valve solutions for fluid handling and pneumatic systems. 

pressure control and flow control

Air Piloted Valves 101 - The Basics

Air piloted valves make use of air pressure to control compressed air, liquids or gas by means of a pneumatic system. Manufacturers prefer these valves because they do not require additional electrical current or labor to operate. This proves especially useful in dirty, wet applications or when operating media in volatile environments could combust or change drastically in the presence of electricity. 

To understand air piloted valves better, we’ve compiled some basic information. We’ll be covering: 

  • What are air piloted valves? 
  • How do they work? 
  • What applications are they best suited for? 
  • What makes ours unique? 
  • What to do if you need custom air piloted valves for your system 
  • What Are Air Piloted Valves? 

Air piloted valves are operated with pneumatic pressure, and typically by the output of other pneumatic valves. They are configured as 2 and 3-port types to control pressurized liquids and gases such as water and chemicals, or as 2, 3 and 4-way types controlling compressed air (or vacuum) in industrial automation applications. 

Often, they contribute to simpler, more reliable and cost-effective solutions in media control problems, using smaller and/or fewer solenoid or manual piloting valves mounted away from the point of use.

They are commonly used in applications where the presence of electricity or manual labor may be hazardous. Additionally, air piloted valves are used in situations where an air pressure-based operating method is already in place. For example, outputs of other solenoid or manual valves can perform their work but also pilot operate these valves for simultaneous functions.

Other Terms for Air Piloted Valves

Some manufacturers and retailers may use these synonymous terms in place of “air piloted valves” to control liquids and gases in process applications for compressed air in pneumatic applications:

  • Air Operated Valves 
  • Remote Air Pilot Valves
  • Air Operated Slave Valves
  • Air Piloted Pneumatic Valves
  • Air Piloted Process Valves
  • Air Operated Pneumatic Valves
  • Air Operated Directional Control Valves
  • Pneumatically Operated Valves

How Do Air Piloted Valves Work? 

Air piloted valves use the force of compressed air on the effective area of a piston or diaphragm to shift into an actuated position. The manufacturer will specify a minimum pilot pressure requirement relative to the pressure being controlled.  

At Humphrey, we offer a variety of industry-standard and specialty function 2, 3, and 4-way air piloted valves for industrial pneumatic and low pressure, mild liquid applications. Our extremely reliable, diaphragm-poppet types are unique to industry with configurations for vacuum, dirty air, ultra clean air or mild liquids.

What Are Some Benefits of Air Piloted Valves? 

Air piloted valves can offer the following high-level benefits to end-users:

  • Cost savings: Require smaller, more efficient piloting valves, and utilize less compressed air when mounted near the point of use. Less expensive than solenoid and manually operated valves.
  • Reliable: Simple construction with few parts. High shifting forces and tight sealing. 
  • Safety: Reduces risk and more reliable when operating in hazardous or dirty environments. 
  • Amplified, high flow capacity: Excellent alternative when most flow requirements in the system are satisfied, but a few require amplified, high flow.

What Applications Are They Best Suited For?

Though not every type of valve will prove useful across all applications, air piloted valves are incredibly versatile. Some of the ways that they are used can include, but are not limited to:

  • Slave valves in simultaneous functions
  • Lockout valves in interlocking functions
  • Simple alternative when amplified, high flow capacity is required 
  • A safer alternative in hazardous or difficult environments 
  • Reliable in poor or unstable compressed air conditions 
  • Transitioning valves from lubricated, dirty air to clean dry air or alternate media
  • Consuming less compressed air than other solutions 

The Humphrey Difference

We design our products around our Classic Diaphragm-Poppet Series. This unique air piloted valve construction cannot stick and will not leak. 

Different from spool valves, diaphragm-poppet air piloted valves eliminate sliding seals that stick and wear with time. The design is also popular when “dirtier” system air needs to be isolated from clean, instrument quality air, or inert gas. 

Humphrey diaphragm-poppet air piloted valves are offered in optional brass and stainless steel bodies for use with gases and liquids as well as corrosive environments. This results in exceptional performance and reliability with certain alternative media.

Industry Standard Doesn’t Cut It? Try Humphrey Engineered Solutions

Sometimes, your system needs go beyond what the market-variety valves can provide. This is not unusual. In fact, one of the most frequent requests we receive from customers is to tailor the air piloted valve to their specific requirements. 

If your system does not or can not utilize industry-standard air piloted valves, we can help. We specialize in creating engineered solutions that more closely align with your needs without sacrificing performance or durability.

Get Better Air Piloted Valves

If you are interested in learning more about air piloted valves or understanding how you can implement better solutions into your systems, we are here to help. Contact us anytime for additional information.


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air piloted valves

Improve Seal Performance in Aggressive Media Applications

FFKM test comparison
Now Available from Humphrey Products: 350/351 iDP Valves with FFKM Elastomer
FFKM (left) exhibits less volume swell than standard elastomer (right) in aggressive media applications.

While O-rings and sealing components made from other elastomers are prone to failure when exposed to steam, caustic and hazardous media, FFKM (perfluoroelastomer) offers near-universal chemical compatibility.

With superior inert properties, FFKM resists volume swell when exposed to more than 1,800 chemicals, solvents, and plasmas, including:

  • Acetic Acid
  • Concentrated Nitric Acid
  • Sodium Hydroxide
  • Ethylene Diamine
  • Steam

FFKM elastomers can withstand the harshest conditions, including those found in medical applications where aggressive agents and/or steam are used for sterilization and semiconductor manufacturing where oxygen plasma is present.

FFKM Features

  • Excellent chemical resistance (best in class, similar to PTFE)
  • Excellent gas and liquid permeation resistance
  • Excellent weather ability and ozone resistance
  • High Density
  • Good mechanical properties, improving sealing performance

The addition of FFKM to the 350 and 370 series iDP family allows engineers to use one valve style in a system that applies both aggressive media and other media. 

The proven reliability of FFKM seals in demanding applications may also allow for longer preventative maintenance schedules, resulting in lower costs. At the same time, process throughput, productivity and yields are enhanced from increased equipment uptime.

For more information, contact Humphrey Products online or call 1.800.477.8707

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idp 350-351 blog image

Super Quick Exhausts Enhance Performance of Air Cylinders

Humphrey Super Quick Exhaust valves feature a specially molded shuttle designed for extremely fast response when sensing upstream pressure differential, redirecting downstream pressure to its third port. We offer a size for virtually every need, with pipe ports from 10-32 UNF to 3/4 PIPE.

Our shuttle’s full-formed seating surface provides long life and outperforms flat-disk (sheet stock) diaphragms found in competitive valve designs. Because of its rubber shuttle design, the Humphrey Super Quick Exhaust valve prevents rupture without the need for flow-restricting metal body webbing of other designs. 

There are many practical uses for the cost-effective, versatile Super Quick Exhaust valves. 

Lubrication Problems: Small-bore pneumatic cylinders and actuators are often poorly lubricated due to the small displacement of air per cycle. Airline lubricant back-flows through the control valve on each exhaust cycle without reaching the cylinder. Oil traces at the control valve’s exhaust port does not prove proper cylinder lubrication.

To solve lubrication problems, close the nipple of the Super Quick Exhaust to the cylinder port. This redirects back-flow and allows progressive oil to flow to the cylinder. 

Air "Spring” Return: Super Quick Exhaust can provide controlled “air spring” return, a potential advantage over the standard spring return cylinders. 

“Air spring” return force can be adjusted by a regulator (1) while providing a method of controlling the cylinder with a more economical 3-way valve (2). Example of use: Cylinder rod (1) extends with high pressure for impact, and rod retracts under lower pressure.

Shuttle Valve: Reduce Air from 3-way valves (1 or 2) always directed to cylinder (3).

High-Low Pressure: Reduce noise, shock, and stress on the air cylinder. Extend rod with low pressure (1) to position rod with workpiece. Switch to high pressure (2) to lock, bend, or reposition workpiece, etc.

Other Humphrey Super Quick Exhaust Functions 

  • Flow Control Valve: Close nipple Super Quick Exhaust air cylinder port. Restrict exhaust flow at Quick Exhaust port 3 and control speed of the cylinder rod by metering exhausting air.
  • Check Valve: Plug port 3 of Quick Exhaust for check function. Allows full flow from port 1 to port 2. Check function occurs from port 2 to port 1.
quick exhaust valve

Redesigned PCD Proportional Valve Driver Marries Trusted Functionality with Improved Control and Flexibility

The Humphrey Team is excited to announce the release of its redesigned ProControl™ Series PCD Proportional Valve Driver. 

Like the original model, the latest PCD proportional valve driver regulates the function of proportional valves through PWM or constant current signals. New navigation buttons provide operators with precision manual control and flexibility for various drive/control inputs. The valve and interface can also be controlled with various data acquisitions, including PLCs, IoTs or closed-loop systems.

PCD Proportional Valve Driver Features

The PCD proportional valve driver is exceptionally versatile. Its customizable interface can control a proportional valve on your test bench for evaluation and then transition to a production environment. You can also integrate the valve and driver into your system and use your DAQ output for valve control.

Input features

  • 0 to 5v, 0 to 10v and 4 to 20mA input options
  • Manual input control via navigation buttons
  • Valve presets for Humphrey valve models PV3, PV10, PC30 and iDP390/391 
  • Customized control mode for other proportional valves 
  • Signal conditioning via linearization attribute 
  • Screwless, push-button clamp connector
  • LCD screen and readout

Output features

  • Constant Current
    • 0 to 1 Amp
    • Dithering: 0 to 40mA
  • PWM
    • Frequency options: 500, 1.25k, 2.5k, 5k or 10k Hz
    • Duty Cycle: 0 to 100%
    • Dithering: 0 to 10%

Contact our ProControl™ application specialist at 1.844.447.9009 or email for more information and setup assistance.

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PCD Proportional Valve Driver

HK5/HKL5 Miniature Diaphragm Poppet Valve Offers Practical Solution for Alternate Media Application

HK5/HKL5 Miniature Diaphragm Poppet Valve The unique construction of the direct-acting HK5 solenoid valve makes it ideal for use in precise applications for clean, dry air, alternate media, and inert operation.

The miniature diaphragm poppet design flexes as it shifts, eliminating the need for sliding seals, seal wear, and metal-on-metal contact. This design ensures media integrity over a long service life.

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Solenoid Valves Offer Application Flexibility

The HK5 and HKL5 diaphragm valve series is a compact, flexible solution for controlling gases and fluids. Its multipurpose function and flexible construction make the solenoid valve series user-friendly. The design can offer zero leakage in specific applications. The HKL5 model is designed for compatible liquids and gases found in analytical instrument applications. Download the brochure for more information.

Download Brochure


HK5 and HKL5 Miniature Solenoid Valve Features

The Humphrey HK5 Series 2-way and 3-way, single solenoid valve provides performance and versatility for multi-media applications.

Product advantages:

  • Diaphragm-poppet design is inert to media
  • Versatile plumbing, electrical, and mounting features
  • Quiet operation 
  • Multi-function: 2-way or 3-way, normally closed or normally open, diverter or selector 
  • Excellent flow characteristics for a small, light, compact component: 85 LPM at 100 psi
  • Direct operating: stable performance throughout the spectrum of 28” Hg to 100 psi
  • Multi-million life cycle
  • RoHS compliant
  • Made in the USA

Application advantages:

  • Media is isolated from the solenoid
  • All wetted surfaces are inert materials
  • Low leakage with bubble-tight applications available


A Track Record of High-Quality Solenoid Valve Applications

Humphrey’s HK5/HKL5 Miniature Diaphragm-Poppet Valve has years of experience with difficult applications. Several Engineered Solution designs have been developed and centered around the flexibility and capabilities of the HK5.

Learn more with our case history illustrations of satisfied customer applications:

Complimentary Test & Evaluation Valve Offered for Qualifying Applications

This special offer is to the OEM design engineer seeking to test and qualify valves for a current problem or upcoming project. 

Our valves are ideally suited for the equipment or device manufacturer requiring reliable, cost-effective control of fluid media in their product... from basic compressed air and vacuum pressure through, to the more difficult control of liquid chemicals and cleaning agents. Compact in construction and designed for flexibility, the valves can be engineered to fit in when space is constrained.

To preview our wide selection of valve products, click here to access the online catalog.

Interested engineers are requested to complete the form below and submit. A Humphrey factory representative will call to assist with valve selection and shipment. 

Alternately, download the fillable form here and return it via fax or email, or call 800-477-8709 to speak with a sales representative.

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