Instructions
9.2 PID_3Step
PID control
312 Function Manual, 03/2017, A5E35300227-AC
Mode of operation of PID_3Step V2
Monitoring process value limits
You specify the high limit and low limit of the process value in the Config.InputUpperLimit
and Config.InputLowerLimit tags. If the process value is outside these limits, an error occurs
(ErrorBits = 0001h).
You specify a high and low warning limit of the process value in the
Config.InputUpperWarning and Config.InputLowerWarning tags. If the process value is
outside these warning limits, a warning occurs (Warning = 0040h), and the InputWarning_H
or InputWarning_L output parameter changes to TRUE.
You specify a high limit and low limit of the setpoint in the Config.SetpointUpperLimit and
Config.SetpointLowerLimit tags. PID_3Step automatically limits the setpoint to the process
value limits. You can limit the setpoint to a smaller range. PID_3Step checks whether this
range falls within the process value limits. If the setpoint is outside these limits, the high or
low limit is used as the setpoint, and output parameter SetpointLimit_H or SetpointLimit_L is
set to TRUE.
The setpoint is limited in all operating modes.
Limiting the output value
You specify a high limit and low limit of the output value in the Config.OutputUpperLimit and
Config.OutputLowerLimit tags. The output value limits must be within "Low endstop" and
"High endstop".
● High endstop: Config.FeedbackScaling.UpperPointOut
● Low endstop: Config.FeedbackScaling.LowerPointOut
Rule:
UpperPointOut ≥ OutputUpperLimit > OutputLowerLimit ≥ LowerPointOut
The valid values for "High endstop" and "Low endstop" depend upon:
● FeedbackOn
● FeedbackPerOn
● OutputPerOn
TRUE FALSE FALSE Cannot be set (0.0%) Cannot be set (100.0%)
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