Siemens S-400 Reversing Bit

Does anybody know how to take a setpoint number and reverse it based on 100. In other words If I set my DB2.DBD10 to 75 (Floating Point)then have a convertor or some type of math bit convert it to 25... Or say if I put in 65 then I could get 35 out of it. If I put in 50 I would get 50 If I put in 22 I would get 78 do you understand?

Thanks

Jim

Hmmm .... seems easy enough, but as ever, no doubt there are hidden traps. Anyway I'll just jump right in ...

You obviously need a second register either to hold the value you enter or the result. Let's assume you want the result in DB2.DBD10. So declare a temporary variable to hold the value you enter. Let's call this, oh, I don't know, #Setpoint, OK?

And then ...

 

 L 100.0     // Establish value of 100 in accumulator

 L #Setpoint // Load your setpoint ...

 -R          // ... do a floating-point (Real) subtraction ...

 T DB2.DBD10 // ... and store the result.

 

All right, what have I missed?

Ken

What result you like for 122 ?

Oh, Seppo,

Why did you have to ask that?!?
It will probably turn out that this is some really weird-shaped curve with loads of hysteresis, and the section between 0 and 100 is the only linear portion!

Ken