Log Base 10 (LOG)
The LOG instruction takes the log base 10 of the Source and stores the result in the
Destination. The Source must be greater than zero or a minor fault will occur.
Available Languages
Ladder Diagram
Structured Text
This instruction is not available in
structured text. However, in the Structured Text Editor you can use LOG as an operator in an
expression to compute the same result. Refer to Structured Text syntax for more information on the syntax of expressions and assignments within structured text.
Operands
IMPORTANT:
Unexpected operation may occur if:
- Output tag operands are overwritten.
- Members of a structure operand are overwritten.
- Except when specified, structure operands are shared by multiple instructions.
There are data conversion rules for mixing numeric data types within an instruction. See
Data conversions.
Ladder Diagram
Operand | Data Type | Format | Description |
|---|---|---|---|
Source | SINT INT DINT LINT USINT UINT UDINT ULINT REAL LREAL | Immediate tag | Value for which the instruction finds the log. |
Destination | SINT INT DINT LINT USINT UINT UDINT ULINT REAL LREAL | tag | Tag to store the result of the instruction. |
Affects Math Status Flags
Yes
Major/Minor Faults
None specific to this instruction. See Index through arrays for array-indexing faults.
Execution
Ladder Diagram
Condition/State | Action Taken |
|---|---|
Prescan | N/A |
Rung-condition-in is false | Set Rung-condition-out to Rung-condition-in. |
Rung-condition-in is true | Set Rung-condition-out to Rung-condition-in. Dest = value of log base 10 of the Source. |
Postscan | N/A. |
Examples
Ladder Diagram
Structured Text
result :=
LOG(value);
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