GFK-2950C February 2018 343
Chapter 7 PID Built-In Function Block
This chapter describes the PID (Proportional plus Integral plus Derivative) built-in function block,
which is used for closed-loop process control. The PID function compares feedback from a process
variable (PV) with a desired process set point (SP) and updates a control variable (CV) based on the
error.
The PID function uses PID loop gains and other parameters stored in a 40-word reference array of
16-bit integer words to solve the PID algorithm at the desired time interval.
Figure 14: PID in Ladder Diagram
Figure 15: PID in Function Block Diagram
This chapter presents the following topics:
▪ Operands of the PID Function
▪ Reference Array for the PID Function
▪ Operation of the PID Function
▪ PID Algorithm Selection (PIDISA or PIDIND) and Gain Calculations
▪ Determining the Process Characteristics
▪ Setting Tuning Loop Gains
▪ PID Example
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