User Manual

PID is easy
8.1 Inserting the PID instruction and technology object
Easy Book
Manual, 03/2014, A5E02486774-AF
171
8.1
Inserting the PID instruction and technology object
STEP 7 provides two instructions for PID control:
● The PID_Compact instruction and its associated technology object provide a universal
PID controller with tuning. The technology object contains all of the settings for the control
loop.
● The PID_3Step instruction and its associated technology object provide a PID controller
with specific settings for motor-activated valves. The technology object contains all of the
settings for the control loop. The PID_3Step controller provides two additional Boolean
outputs.
After creating the technology object, you must configure the parameters (Page 188). You
also adjust the autotuning parameters ("pre-tuning" during startup or manual "fine tuning") to
commission the operation of the PID controller (Page 190).
Table 8- 1 Inserting the PID instruction and the technology object
When you insert a PID instruction into your user program,
STEP 7 automatically creates a technology object and an
instance DB for the instruction. The instance DB contains
all of the parameters that are used by the PID instruction.
Each PID instruction must have its own unique instance
DB to operate properly.
After inserting the PID instruction and creating the
technology object and instance DB, you configure the
parameters for the technology object (Page 188).