The FC-2920 Series Mass Flow Controllers and Flowmeters accurately and reliably measure and control the mass flow rate of gases up to 200 slm (420 scfh) of Nitrogen equivalents. The FC-2921 offers a 15-pin D connector with optional 4-20 mA DC signals. The FM-3920 and FM-3921 are flowmeters with the same specifications and dimensions as the FC-2920 and FC-2921 respectively.
The FC-2920 Mass Flow Controller consists of a thermal gas flow sensor, adjustable bypass flow splitter, adjustable solenoid control valve and electronics. Tylan General developed thermal mass flow controllers over twenty years ago and is the worldwide leader today.

Accuracy
Tylan General’s thermal differential flow sensor provides highly accurate and repeatable mass measurement of gas flow. Because the sensor measures the mass flow of gas, it is independent of pressure and temperature changes. This ensures that flow are consistent in different systems or locations.

Thermal Gas Flow Sensor
The FC-2920 measures gas flow rates using Tylan General's patented temperature differential sensing device. The temperature difference of gas flowing past two heated, resistive temperature sensors is directly proportional to the mass flow rate of the gas. An insulated small diameter capillary is used in the sensing element which greatly reduces variations with attitude. This allows the FC-2920 to be mounted in any position.

Bypass Flow Splitter 
The bypass flow splitter smooths the primary gas flow into the laminar flow region and produces sufficient pressure drop to range is set by adjusting the length of the stainless steel mesh bypass. 

Solenoid Control Valve
The control mechanism is a normally closed proportional solenoid valve which is easily adjusted and provides fast response. A hex head screw on top of the valve adjusts the stroke of the valve while the body of the valve can be turned to adjust valve closure. Except for the dynamic plunger, all gas wetted metal surfaces are of 316 stainless steel. The plunger is 446 stainless steel.

PID On-Board Control
 On-board PIO control circuitry allows the FC-2920 to control the gas flow to a desired setpoint. A command setpoint of 0-5 VDC is sent to the FC-2920 which compares it to the flow reading and then modulates the control valve to achieve the desired flow rate. The response to setpoint command is less than six seconds. A 0-5 VDC output signal is returned which indicates gas flow . Optional 4-20 mA DC current signals are available on the FC-2921 and FM-3921 version along with a 15-pin D connector.

Autozero Circuit
Long-term repeatability is enhanced in the FC-2920 by a digital circuit which automatically resets the output to zero under no-flow conditions. This feature, standard in all FC- 2900 MFCs shifts the entire calibration curve to cancel many of the effects of temperature coefficient and calibration drift.