Standard PID function with additional features such as built-in start‑up ramp, direct-reverse action selection, integral recalculation to prevent windup below minimum/above maximum, and an auxiliary input for limit applications and integral reset.
The following diagram compares the system response characteristics of the PID versus the EPID.
When the input "Enable" is turned on, the EPID output starts at the desired "Output start value" and changes slowly as needed to bring the controlled variable "TempInput" to its "Setpoint". "Start ramp time" controls the rate of change of the output during the start‑up period. Specifically, "Start ramp time" is the minimum amount of time it takes for the output to go from the output start value to either 0 or 100 percent. The input "Auxiliary" is primarily intended for applications where EPID is used for high or low limit applications.
When the enable input is off, the EPID output is set to the "Output start value"
Ctrl_Out = output (Parameter P1 controls action of output, 0 = direct action, 1 = reverse action)
Ramp = start ramp value (0-100 pct)
The input "Output start value" controls the initial value of the output at the beginning of the start ramp period. This value is also present at the output when the enable input is off.
The output "Ramp" goes from 0 to 100 during the start‑up ramp period. (Provided for diagnostic use, if desired.)
The input "Start ramp time" sets the duration of the start ramp by controlling the value of internal Parameter P7. You should not directly set the value of P7.
The integral component is not saved directly. Instead, the proportional and derivative values are used to determine what the integral component should be to produce the current output value. If the output falls to minimum or rises to maximum or is overridden by the input "Auxiliary", the integral component is calculated so that it is consistent with the actual output.
The following diagram illustrates the two outputs, "Ctrl_OUT" and "Ramp", of EPID.