Siemens S7-1200 - Creating a Complex Equation with a Simple Instruction

STEP 7 programming software
2.3 Easy-to-use tools
S7-1200 Programmable controller
System Manual, 03/2014, A5E02486680-AG
39
2.3.3
Creating a complex equation with a simple instruction
The Calculate instruction lets you create a math fun
ction that operates on multiple input
parameters to produce the result, according to the equation that you define.
In the Basic instruction tree, expand the Math functions folder.
Double
-click the Calculate instruction to insert the instruction
into your user program.
The unconfigured Calculate
instruction provides two input
parameters and an output
parameter.
Click the "???" and select the data types for the input and output
parameters. (The input and output parameters must all be the same
data type.)
For this example, select the "Real" data type.
Click the "Edit equation" icon to enter the equation.
For this example, enter the following equation for scaling a raw analog value. (The "In" and
"Out" designations correspond to the parameters of the Calculate instruction.)
Out
value
= ((Out
high
- Out
low
) / (In
high
- In
low
)) * (In
value
- In
low
) + Out
low
Out
= ((in4 - in5) / (in2 - in3)) * (in1 - in3) + in5
Where:
Out
value
(Out)
Scaled output value