The QB4 closed loop electronic pressure regulator can handle flow rates as high as 200 scfm forward flow and 300 scfm exhaust flow. It works with pressures from vacuum to 150 psig. The unit is made up of two solenoid valves, an internal pressure transducer and an electronic control circuit mounted to an integral volume booster. Output pressure is proportional to an electrical input (command signal). Command signals come in a choice of either a differential 0-10 Vdc or 4-20mA. The QB4 also provides an electrical monitor signal for output to a panel meter or controller for data acquisition or quality assurance needs. It is the actual work pressure that is sensed and fed back to the control circuit so any mechanical hysteresis of the air piloted volume booster is automatically compensated for allowing for extraordinary accuracy and repeatability. The volume booster has no stamped gaskets or special molded diaphragm or seal parts. All of the parts related to normal maintenance are standard o-rings.