Auxiliary input function

The input "Auxiliary" can prevent integral windup when EPID is used in a limit application. In this case, you pass a control signal from some other PID controller through the EPID before going to the controlled device. This control signal passes through unchanged unless the EPID input rises above its setpoint on a high limit or falls below its setpoint on a low limit. The auxiliary input mode parameter must be set correctly depending on whether the EPID is reverse- or direct-acting and on whether it is imposing a high or low limit. If this parameter is set to +1, then the auxiliary signal is maximized with the internal PID signal. If the parameter is a -1, then the auxiliary signal is minimized with the internal PID signal. A parameter value of zero causes the auxiliary input value to be ignored.

For direct-acting low limit and reverse-acting high limit, set P8 to -1. For reverse-acting low limit or direct-acting high limit, set P8 to +1.