Fb 41

Amr Hassan

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Join Date
May 2005
Posts
340
i am using fb 41 for pid control
how can i make a reverse action , i mean the valve closes when the pv increase
i was thinking to use 100-manipulated value is that correct
 
Amr Hassan said:
i am using fb 41 for pid control
how can i make a reverse action , i mean the valve closes when the pv increase
i was thinking to use 100-manipulated value is that correct
Click to expand...

Are you referring to S5 or S7? In S5 the sign of the K factor determined the action of the PID

Ian
 
Hello Hassan;
We are refering to the GAIN parameter (proportional gain). Setting this to a negative value will reverse the action of the PID block to the manipulated value (LMNPER).
From Siemens' website:

Reversing the direction of control action of the controller "CONT_C" (SFB41/FB41)
QUESTION:
How can I reverse the direction of control action of a controller, e.g. the "Continue_Control" (SFB41/FB41)?
ANSWER:
You can reverse the direction of control action of a controller by entering a negative value for the gain at the "GAIN" input of the controller.
More information is available in the Online Help for STEP 7.
Keywords:
Controller block, Continue_Control


Entry ID:8718842 Date:07/09/2003


Setting the LMNPER parameter at 100.0 (REAL value), in maual mode, will force your output to 100%. In auto mode, it will have no effect, as the PID block will calculate the output required to minimize the error.
Setting the GAIN to a negative value will produce a negative LMNPER value, which will cause your valve to close when the error increases.

Hope this helps,
Daniel Chartier
 
I Have did the Same

Hassan

I have the same before, and i did like what you are saying and it is working fine. you may do it, and it will work
 
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