Closed Loop Control for Pneumatic Proportional Valves
Proportional solenoid valves provide precise performance to control media flow in pneumatic operating systems. They open to a specific flow rate based on the amount of amperage applied to the coil and sustain varying positions based on media pressure.
Closed-loop controls are commonly used in high-tech equipment to regulate media flow. Unlike open-loop systems, a closed-loop design has a downstream sensor that provides continuous feedback on the downstream flow. That information allows the valve to adjust the flow to meet the previously prescribed flow rate.
How Dynamic Closed-Loop Flow Control Systems Work
System components include:
- An upstream pressure regulator
- A proportional solenoid valve
- A downstream flow transducer
- Control software (analog I/O)
The regulator maintains usable supply pressure. The proportional valve opens to let downstream flow in at a prescribed rate. The transducer continuously reads the downstream flow and provides feedback to the control software.
The software then sends an output to the proportional valve to increase or decrease flow. The slightest change will result in an instant system response to maintain consistency.
Advantages of Proportional Valves in Closed-Loop Systems
When compared to digital on/off solenoid valves, proportional valves offer:
- Efficient responses to dynamic flow changes
- Smooth transitions with less “overshoot”
- Mechanical and electrical noise reduction
- Less wear and tear on the valve’s internal components
- Valve positioning even with minor changes
Closed-loop systems provide:
- Continuous responses to minor pressure and flow changes
- Extremely precise control
- Stability, accuracy and flexibility
- Compensation for variation in components and operating conditions
Humphrey ProControl™ Proportional Valves
Our miniature and small proportional solenoid valves deliver variable control of compressed air and inert gas based on input current to the solenoid. They’re available for inline or subbase mounting and offer excellent resolution and cycle repeatability.
PV3 Miniature Proportional Solenoid Valves
- 10-32 UNF ports
- 32 LPM maximum flow
- 4 watt at full flow
PV10 Hi-Flow Miniature Proportional Solenoid Valves
- 10-32 UNF ports
- 80 LPM maximum flow
- 8 watt at full flow
PC30 Small Proportional Solenoid Valves
- 1/8 NPSF ports
- 225 LPM maximum flow