Inverse signal

[kevbloke]

Hi all. I have had a pressure sensor die and the only one i can find is working back to front.
Can anyone tell me what i can do in step7 to inverse the signal from PIW370 in my program please. Is there a simple command i can put in?

 

[BryanG]

OK, sometimes you have to stop thinking like a PLC programmer and instead go back to first principles. If I had a 0-10 range with a value of 2. what would be the inverse...... 8. How do you get there.... 10 minus 2. So the simple command is a subtraction. You might have to get a bit more complicated if the range doesn't start at zero.

 

[robb676]

Try reversing the leads..

 

[BryanG]

Had a bit more time to think and if you want a more complex solution then use a 'Scaling' routine. Disadvantage it takes longer to process, Advantage it takes care of any offsets within the routine.

 

[kevbloke]

Thanks for your help guys, i found an identical unit on another machine. Sorted.