The Alicat Scientific PCD series pressure controller utilizes independently controlled intake and exhaust valves to achieve fast and stable pressure control inside a closed, or dead headed, system. Systems with no in-line flow that require pressure control have previously required installation of a relief valves for pressure control. This method, although effective, resulted in wasted process gas, poor repeatability, and poor accuracy. The Alicat PCD series dual valve pressure controller eliminates the need for bleed ports and relief valves.

The Alicat PCD is available in gauge and absolute ranges to 3,000 psi as well as differential ranges to 100 psi. Using a modified PID closed loop control and a proportional control on each valve results in a total full scale accuracy of ± 0.25% across all ranges. The modified loop and proportional control not only produces increases in precision control of the process pressure in closed or nearly closed systems, it also eliminates dead-band that is inherent in other pressure controllers that use pressure switches and on/off valves.

The Alicat PCD series pressure controller uses only one valve at a time automatically switching the PID control to the required valve. By opening and closing one valve at a time, gas venting required to maintain a setpoint is significantly reduced. The PCD pressure controller has been used in a variety of industries ranging from semiconductor manufacturing to biopharmaceutical testing.