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Control valve with 4-20mA output


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I have one analoge input 4-20mA from a flow meter. Scaled to 0-100.


I need to send out 4-20mA to my control valve depending on that input. In example, if the input from flow meter is 12mA (50) I need the valve to half close 12(mA).



What will be the correct way to solve this with ladder in unilogic software? I see no need for PID.


I have used MOV blocks before, but that is not available here.






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Upon adding an I/O module to the hardware configuration, an I/O struct is automatically created for your with the registers where that I/O information will be held.  You can find the I/O struct through the I/O tab in the bottom window of the UniLogic software.


For instance, if I add a UIA-0402N module to the configuration, the software automatically creates the UIA-0402N_X struct for me.  Now If I wish to reference and analog input from the card, I can call it through the struct (i.e. UIA-0402N_X.Input[input_0]) or via its Alias name (which you can define yourself).


For more information on this subject, please watch our Youtube tutorial on the UniLogic hardware configuration here.


Hope this helps.

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Using the store function you do need to verify both values work the same way.


At 12ma the valve my be half open/closed but is it open or closed at 20 ma?  If you're reading 18 ma, should the valve be more open, or more closed?


If they are an inverse of each other you'll need to use the linearize function to get the right output, if it's direct, then STORE works fine.

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  • 1 month later...
Thank you all for your answers.


Maybe I do not understand.

Scale same?

You think that corresponds to the measured temperature is real? This would be conform by other measuring devices.

I do not know how to set those values.

I would need to show how well these 19 values ​​set.

Then I'll understand what I'm doing wrong.

And in the future, I am already set up himself. Help helped me :-(.



for set(For temperature 900+-9):

Set clue                                                                  900

Process Values                                                      950                                          

Proportional band                                                  1 

integral time                                                           20                                                                                           

derivative time                                                        5

sample time                                                           10000                             

input low limit                                                          895                                     

high input LMIT                                                     905                                              

ouput low limit                                                        -10                                                 

output high limit                                                    10       

reverse action                                                       0      

pid mode                                                              0

control value                                                         0                                                        

status                                                                   -6

autotune done                                                       0

control value proportional                                      0

control integral value                                             0

control value derivative                                         0

integral eror                                                          0


Process Values is input temperature.
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