FQB2 Mass Flow Controller

The FQB2 Mass Flow Controller is another complete flow control package from Proportion-Air. The FQB2 electronically modulates the pilot of any of a variety of mechanical flow amplifiers (Generally, the PSR-Series). Proportion-Air selects the appropriate mechanical flow amplifier based on your specific application’s flow control parameters.

An F-series air flow transducer is used to feed an electronic signal representing the mass flow rate of air back to the FQB2 control valve circuit. This makes a complete flow control package which electronically controls the flow of air independent of supply pressure or varying system restrictions. The FQB2 mass flow controller has a standard turndown ratio of 10:1 – Ask about our 20:1 turndown ratio option.

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Accuracy ±


Repeatability ±

Max Flow (SCFM)

Max P1 (PSI)

FQB2 Downloads & Links
Documents Links Downloads
Installation Guide F-Series Flow Transducer FQB2_Schematic Symbol
Sales Brochure File Request Form
FQB2 Downloads & Links
Installation Guide
Sales Brochure
F-Series Flow Transducer
FQB2_Schematic Symbol
File Request Form
FQB2 Technical Specifications
Max Inlet Pressure Accuracy Repeatability Lowest Control Flow
150 PSI (10.34 Bar) ±4% F.S. ±0.25% F.S. 3 to 30 SCFM (85-850 LPM)
Port Size Durability Ambient Temps Media Temps
1/4″  to 1-1/2″ NPT (BSPP Available) Immune to shock & vibration (up to 20 Gs) 32-158°F (0-70°C) 32-122°F (0-50°C)
Turn-Down Ratio Filtration Power Requirement
10:1 (inquire about 20:1) 40 Micron 17-24 VDC
FQB2 Technical Specifications
Max Inlet Pressure
150 PSI (12 Bar)
Minimum Inlet Pressure
15 PSI (1 Bar)
±4% F.S.
±0.25% F.S.
Lowest Control Flow Range
3 to 30 SCFM (85-850 LPM)
Turn-Down Ratio
10:1 (Inquire about 20:1)
Port Size
1/4″ to 1-1/2″  NPT (BSPP Available)
Immune to shock & vibration (up to 20 Gs)
Ambient Temps
32-158°F (0-70°C)
Media Temps
32-122°F (0-50°C)
Temperature Sensitivity
0.25% / °C
40 Micron
Protection Rating
FQB2 Mass Flow Controller

FQB2 Mass Flow Controller


The FQB2 Mass Flow Controller is a proportional compressed gas flow control assembly. The assembly consists of an FQB2-Series proportional control valve, a PSR volume booster and an F-Series high speed flow transducer. The FQB2 control valve consists of two normally closed solenoid valves, a control circuit board and an IP65 protective canister.

The FQB2 operates by comparing the user’s electronic command input signal to the signal that is returned to the FQB2 from the F-Series flow monitor. The on-board control circuit examines any differences between these signals and actuates the solenoid valves in response. Opening one solenoid valve removes compressed gas from the dome of the PSR (which causes the PSR to exhaust downstream gas) while opening the other solenoid valve adds compressed gas (to the dome of the PSR) from the supply. The volume of compressed gas on the dome of the PSR regulator sets the output flow rate. The FQB2 Mass Flow Controller continuously monitors the user command and F-Series feedback signals to keep the assemblies flow rate at the desired point.


Flow Control Models

with subtle differences and important implications




Requires a known and fixed regulated supply pressure to maintain calibration



Compensates for fluctuations in inlet pressure (up to 50%) to maintain calibration



Requires output port open to atmosphere. Most commonly used in cylinder speed control. 


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