Instructions
9.1 PID_Compact
PID control
Function Manual, 03/2017, A5E35300227-AC
249
Mode of operation of PID_Compact 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_Compact automatically limits the setpoint to the
process value limits. You can limit the setpoint to a smaller range. PID_Compact 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. Output, ManualValue and SubstituteOutput are limited to
these values. The output value limits must match the control logic.
The valid output value limit values depend on the Output used.
Output_PWM 0.0 to 100.0%
Rule:
OutputUpperLimit > OutputLowerLimit
Note
Use with two or more actuators
PID_Compact is not suitable for use with two or
more actuators (for example, in
heating/cooling applications), because different actuators need different PID parameters to
achieve a good control response. Use PID_Temp for applications with two actuators acting in
opposite directions.
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