PID GAINS IN SIEMENS 300 series

[ravilal]

WHY THE PID(PROPORTIONAL,INTEGRAL AND DERIVATIVE) HAS SAME GAIN VALUE IN SIEMENS 300 SERIES.HOW CAN I INSERT DIFFERENT GAIN VALUE,i.e different proportional gain,different integral gain, and different derivative gain?

 

[dchartier]

Hello ravilal;

I will presume you are using FB41 in Step 7; the flow diagram for this function is illustrated below:

The input and output symbols of this diagram represent the parameters of FB41. You will find Gain, Ti and Td on the diagram; these represent Proportional gain, Reset time and Derivative time; whatever value you enter here (a REAL numerical value, or preferably a REAL variable from your program) will be the different gains of your controller. Notice that the BOOL values P_Sel, I_Sel and D_Sel must be ON in order to select the gains (these BOOL switches sallow you to select a P-only controller, a PI controlle, a PID controller...).

Hope this helps,
Daniel Chartier

 

[Pandiani]

Just be sure to place your FB41 block in OB35, it will save you from frustration I had when tried to tune PID controller for the first time. Otherwise, time constants Ti and Td won't mean anything.

 

[ravilal]

Factors And Offsets In Pid In Step 7

Thanks for answering.Can you tell me when and where do we use
PV_FAC and PV_OFF used in PV NORM block in PID loop in FB41 of siemsns S7? and similarly LMN_FAC and
LMN_OFF in LMN NORM block.What are practical applications of using
these factors and offsets in these blocks.what are their uses?what are they for?