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 649B, 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.