Description
You can use the "Form natural logarithm" instruction to calculate the natural logarithm to base e (e = 2.718282) of the value at input IN. The result is sent to output OUT and can be queried there. The instruction has a positive result if the input value is greater than zero. If input values are less than zero, output OUT returns an invalid floating-point number.
The enable output ENO has the signal state "0" if one of the following conditions applies:
-
Enable input EN has the signal state "0".
-
The value at input IN is not a valid floating-point number.
-
The value at input IN is negative.
Parameters
The following table shows the parameters of the instruction "Form natural logarithm":
|
Parameters |
Declaration |
Data type |
Memory area |
Description |
|
|---|---|---|---|---|---|
|
S7-1200 |
S7-1500 |
||||
|
EN |
Input |
BOOL |
I, Q, M, D, L or constant |
I, Q, M, D, L, T, C or constant |
Enable input |
|
ENO |
Output |
BOOL |
I, Q, M, D, L |
I, Q, M, D, L |
Enable output |
|
IN |
Input |
Floating-point numbers |
I, Q, M, D, L, P or constant |
I, Q, M, D, L, P or constant |
Input value |
|
OUT |
Output |
Floating-point numbers |
I, Q, M, D, L, P |
I, Q, M, D, L, P |
Natural logarithm of the input value |
You can select the data type of the instruction from the "???" drop-down list of the instruction box.
For additional information on valid data types, refer to "See also".
Example
The following example shows how the instruction works:
If the "TagIn" operand has signal state "1", the instruction is executed. The instruction forms the natural logarithm of the value at input "Tag_Value" and sends the result to output "Tag_Result". If the instruction is executed without errors, the "TagOut" output is set.