Thermal mass flow controller 1640A

for gas

The MKS Instruments 1640 Pressure-based Mass Flow Controller is a metal-sealed instrument with standard 3-inch footprint, designed to meter and control gas flows in low-line pressure applications where thermal mass flow controllers are limited in their ability to accurately measure flow. The 1640 utilizes the principle of sonic flow through an orifice, a condition met when the upstream control pressure is at least twice the downstream pressure. Under these conditions, mass flow is proportional to the control pressure. In the 1640A Pressure-Based Mass-Flo Controller, a Baratron® capacitance manometer monitors the pressure upstream of the critical orifice. This pressure is proportional to flow. The measured pressure is compared in the control electronics to the flow set point. A control signal is then generated to drive the proportional control valve to the conductance as required to bring the actual control pressure (flow) into agreement with the flow set point.