The 649B Pressure Controller is a single instrument that provides both pressure control and flow metering, replacing multiple component subassemblies. The compact design allows for significant reduction in BWCS (backside wafer cooling systems) size and complexity. The 649 Series Pressure Controller contains a capacitance manometer, mass flow meter, normally-closed proportioning control valve, and closed-loop control electronics. The 649 controls absolute pressure. The pressure transducer is a Baratron® Capacitance Manometer, with Full Scale pressure ranges from 10 Torr to 1000 Torr. Baratron Capacitance Manometers – well-known for their percent of Reading accuracy, stability, and resolution - provide precise measurements at lower pressures and over wider dynamic ranges than strain gage transducers. The patented mass flow sensor provides exceptional zero stability and accuracy of flow measurement. Full Scale ranges from 10 sccm to 5000 sccm nitrogen equivalent are available. The 649 is powered by ±15 VDC at only 300 mA. The default pressure output and input control signals are 0-10 VDC. Two trip points are included in the 649, with LED status indicators, for use as simple on/off process limits. The 649’s control loop tuning parameters are preset for typical installation conditions, but are field adjustable for different conditions and optimum performance. The Proportional and Integral Term adjustments are simple rotary switches, providing a wide dynamic control range. In the 649, a pressure transducer monitors the pressure to be controlled at the downstream end of the controller. Actual pressure is compared in the electronics to the pressure set point signal. An appropriate signal is then generated to adjust the proportioning control valve to bring actual pressure into agreement with the desired set point. The internal control valve can be specified with one of four orifices allowing pressure control in systems with Full Scale flows from 10 sccm to 5 slm.