Proportion-Air manufactures complete closed-loop electronic mass flow controllers that have quick response and the ability to control flow rates from 2 SCFH to 250 SCFM.

These mass flow controllers are industrial quality and can be mounted in any orientation with the ability to withstand intense vibrations while continuing to control flow. Our flow control assemblies are subject to a 10:1 turndown ratio (inquire about 20:1), meaning that we control flow at 10% to 100% of the range with ±0.25% repeatability. The gases we can control include air, argon, carbon dioxide, helium (not bubble tight), nitrous oxide, nitrogen and oxygen. Our mass flow controllers offer <10ms response time.

The building block for all of our mass flow controllers is the F-series mass flow transducer. The F-series uses high speed differential pressure technology to produce an electrical signal proportional to the mass flow of air or gas. This high speed flow signal is able to be used by a wide variety of Proportion-Air mass flow control valves to close the loop directly around air flow. Based on your required flow rate, the F-series mass flow transducer is matched to the appropriate flow control valve and then calibrated specifically to your exact flow range.

Each electronic flow control valve constantly compares your command signal to the transducer signal of the F-Series flow transducer. The control valve then opens or closes (almost instantaneously) to maintain the commanded flow rate.

Three 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.