Alicat Scientific's answer to controlling pressure in a closed volume or system.
Systems with no in-line flow (dead ended systems) that require pressure control have previously had to install relief valves for pressure control inside the closed volume. The Alicat PCD series dual valve pressure controller eliminates the need for bleed ports and relief valves and gives the user.
Speed and Control
By utilizing modified PID loop controls and proportional control, the PCD pressure controller is able to quickly and accurately reach a defined setpoint. Since the PCD uses similar control algorithms as those in the PC Series single valve pressure controllers, the control speed of the PCD is measured at less than 1/10th of a second!
Cost Savings
The 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. Less exhausted gas is less wasted gas. Companies using exotic bottled gases could save thousands of dollars a year by switching to a PCD pressure controller.
Accuracy
The PCD uses a modified PID closed loop control and a proportional control on each valve resulting in a total full scale accuracy of +/- 0.25% for most units. 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.
Repeatability
Processes designed for consistency require instrumentation that is repeatable. The PCD series dual valve pressure controller has an impressive repeatability spec of +/-0.1% of full scale.
The Alicat PCD dual valve pressure controller has been used in a variety of industries ranging from semiconductor manufacturing to biopharmaceutical testing. The PCD pressure controller was created in response to the need for fast, accurate, repeatable and cost effective pressure control instrumentation designed specifically for closed volumes. Historically, closed volume pressure control was done by using a pressure controller or switch and a bleed port. This method, although effective, resulted in wasted process gas, poor repeatability, and poor accuracy.
The PCD dual valve pressure controller works by using a modified PID loop control that enables the instrument control of each valve while only allowing one valve to open at a time. By opening one valve at a time the unit can effectively reach a setpoint quickly and accurately while keeping gas venting to an absolute minimum.
All Alicat PCD series dual valve pressure controller calibrations are NIST traceable.
Class 1 Div 2 version available.
