[5] Common Questions About Miniature Proportional Control Valves

Miniature proportional control valves offer flexibility and reliability in applications that require precision flow and pressure control. We break down the answers to some of the most common questions about these innovative valves.

#1: What Is a Miniature Proportional Control Valve?

A miniature proportional control valve is a small valve that controls media in proportion to the electric current sent to the valve’s solenoid. It’s a compact device that responds to variations in current applied to its solenoid by delivering a corresponding variable media flow output.

#2: How Does a Miniature Proportional Control Valve Work?

A proportional valve consists of two primary components:

A proportional solenoid
A metering device

They are commonly paired with a feedback sensing device in a closed loop system and controlled using DC current or pulse-width modulation (PWM). The proportional valve receives a signal from an external controlling device such as a PC, PLC, logic relay, power supply or potentiometer. The controller delivers a signal to the valve driver which sends a current to the solenoid.

The resulting electromechanical force shifts the plunger and opens a flow path. The greater the input signal, the higher the flow from the valve. All valve elements are proportional, so any change in the input current proportionally alters the distance the valve spool shifts, flow path size and the amount of media.

In closed-loop systems, a transducer monitors the controlled parameter and sends data back to the controller. The controller continuously compares it with the input signals and adjusts for any deviations. That includes cylinder position, output force and fluid flow rate.

#3: What Are Miniature Proportional Control Valve Performance Specs?

Valves are sized by their flow rate at maximum applied /media pressure. Common voltage ranges include 0-10 V and 0- 20 V. A Miniature Proportional Control Valve typically requires a minimum current to begin flow (lift off). This ensures a low leak rate when at rest. Performance levels vary depending on the specific valve and manufacturer.

Humphrey’s ProControl PV Series miniature valve specs include:

7 inches tall by 0.75 inches in diameter
5-8 milli-second full-span response (zero to max current)
Two Models: 0-30 and 0-75 liters/minute flow capacity
Maximum pressures settings ranging from vacuum to 100 psi
2- port inline and manifold mount configurations

Our Miniature Proportional Control Valves are used to control air, vacuum and inert gases. Modifications are available to precisely configure flow control “gain” to specific applications, to increase maximum flow and to improve performance.

#4: Where Are Miniature Proportional Control Valve Used?

MPCVs are used whenever an application demands direct, variable control of air, vacuum, inert gas, or other media. Typical applications include dynamically dispensing controlled amounts of gas or liquid, controlling downstream pressures and accelerating or decelerating cylinders.

MPCVs can be used in the following applications:

Medical equipment
Robotics
Pneumatic systems
Industrial automation
Analytical instruments

MPCVs make testing and measuring equipment more multifunctional and agile so they can perform a variety of flow and pressure-related tasks within a single device. In biomedical devices, MPCVs can control blood pressure or the flow of oxygen to a patient. In analytical instrumentation, these miniature valves can deliver a precise amount of media on demand.

#5: What Should I Consider When Selecting Miniature Proportional Control Valve?

Consider the function your application requires. Proportional valves can perform a multitude of precision flow control functions, such as:

Cycle to Cycle Variable Output: This function performs like a traditional ON/OFF valve, but valve opens only to the specific current and output flow required for that cycle. The next cycle may open to a different current and output flow.

Incremental Output Variable Output: Valve opens to a specific current and output flow and later in same cycle, adjusts to a different current and output flow.

Dynamic Variable Output Flow: Valve opens to a specific current and output flow, but responds to high-frequency adjustments. Typically, these are closed-loop applications where the downstream side of the valve experiences constant and unpredictable change while flow output remains stable.

Other factors to consider when selecting a Miniature Proportional Control Valve include:

Maximum flow capacity required
System pressure (psi)
Control voltage
Installation size and weight restrictions

Humphrey Products’ Miniature Proportional Control Valves

Our ProControl® PV Series proportional valves feature a flexible design with universal functionality that can be customized to specific needs and will easily fit into small spaces. Contact our technical team for assistance in selecting the right valve for your application.

Download the FAQs of Miniature Proportional Valves to get the answers to these questions and more.