Dyna-Flo 4000 Series pneumatic pressure controllers are
the "brains" of a self contained, local pneumatic PID
control loops. The pressure controller detects
the process pressure using a Bourdon tube. The process pressure
is then compared to an operator manually adjusted set point, which
in turn modulates the controller output. The controller pneumatic
output is connected to a final control device, typically a control
valve, that changes the process pressure.