Scaling Function

Manoj M

Member
M
Join Date
Feb 2014
Location
London
Posts
59
Hello Experts,
Need your advice on this. I am using Step7 V5.5 SP4 for my programming. I am using FC105 scaling function to scale 4-20 mA signal to 0-375 rpm. Now the customer has changed the specifications and want me to do the scaling in multiples of 5. For example between 4.11 to 4.32mA the speed should be 5 rpm then from 4.32 to 4.53 it should be 10 rpm ad so on and this will follow up to 375 rpm in the multiples of 5. Can somebody suggest me the simplest way of doing this. Please see attached picture for your reference.

Regards
Manoj

Speed.jpg
 
Can you say "Change Order"? I would use a PID function. You should be able to accomplish your task by configuring the parameters correctly.

Does the Siemens have a For Next capability? Otherwise you would be using GT & LT statements out the wazoo to watch your input and set the output.
 
Hello Webhead,
Thanks for your reply. I can use the GT and LT functions but that seems to be the lengthiest solution for getting upto the speed of 375 rpmand if that is the only solution then I have to do it.

Regards
Manoj
 
Hello Manoj M ,
I do not have development environment right now, but it should work.

Code: 
      L     "Analog Input 0 -->27648"  // 4-20 mA
      ITD   
      DTR   
      L     1.843200e+002    // Half step length  ((27648 / 75 ) / 2))
      +R    
      L     7.500000e+001    // total step's
      *R    
      RND   
      L     L#27648
      /D    
      L     5
      *I    
      T     #RPM

Regards.
 
Hello SHKODRAN,
Thanks for your help. I will give a try to this logic and will let you know the outcome.

Regards
Manoj
 
Hello SHKODRAN,
Thanks for your help. I have tried the logic you said and it is working like a charm.
I cannot thank you enough for this. Really appreciate this.....
 

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