tracking position with real values

I am trying to track position with Siemens ladder logic.

I have only a (real value) from HMI.

Using ADD_R


If input 1 is -1000

and input two is +2000


will out be null or +1000 ?

ChadOut said:

I am trying to track position with Siemens ladder logic.

I have only a (real value) from HMI.

Using ADD_R


If input 1 is -1000

and input two is +2000


will out be null or +1000 ?

Click to expand...

It will be -1000.0 + 2000.0 = 1000.0 = +1.0000e+3)

You might experience rounding errors like +9.99999e+2 or 1.000001e+3.

So you must never compare a real value on sharp equality, it must be compared within dead band limits.

Kalle