In addition to standard proportional only control analog signals, a System 450 control system provides integral control capability and six time integral selections that you can use to set up analog outputs to generate a proportional plus integral signal.
Proportional plus integral (PI) control incorporates a time-integral control action with proportional control action. If correctly set up, a PI control loop can effectively eliminate offset error and enable a controlled system to drive much closer to the preferred setpoint, even under large constant loads. On a properly sized system with predictable loads, PI control can maintain the controlled system very close to the setpoint.
The integration constant that you select establishes the rate at which the control readjusts the analog output signal. The faster the integration constant, the faster the control readjusts the output signal, and the faster the recovery rate of a properly sized and setup control loop. See Table 1 for information on the System 450 control modules with this feature.