Siemens SIMATIC Manual page 74

Examples for the Temperature Controllers
The controller can be changed to manual at the MAN_ON switch. The manual
value can be set at MAN. After a warm restart on the CPU, the controller is in
manual with the heating off.
If you want to tune the controller, set the TUN_ON bit and enter a setpoint at SP.
You can monitor the tuning at the PHASE parameter.
The result of the tuning can be seen at the status words STATUS_H and
STATUS_D.
Putting the Sample into Operation
To put the sample into operation, follow the steps outlined below:
1. Copy the sample to a CPU.
2. If the default cycle time of OB35 (100 ms) no longer exists, set the cycle time
of OB35 to 100 ms in HW Config. If a time error occurs in the cyclic interrupt
priority class, you must extend the cycle time. In this case, the simulation will
run more slowly. When you control the real process, the cycle time of OB35
and the sampling times CYCLE of DB_TCONT_CP and DB_PROC_C must
match.
3. To run the controller tuning, set TUN_DLMN to 20%.
The screenshot below illustrates controller tuning with TCONT_CP:
13
zEn
Process value
The screenshot above shows the controller tuning when heating from ambient
temperature 20°C to the operating point (60°C). Following this, a setpoint step
change from 60°C to 85°C is made within the control zone. The overshoot can be
eliminated by reducing PFAC_SP from 0.8 to 0.6.
6-10
Setpoint
Process value
Manip. variable
Zoom
PID Temperature Control
A5E00125039-02