These operations allow you to compare two variables or a variable with a numerical value. All these operations are conditional; that is, when the comparison condition is met, a binary signal will be activated. In some cases, the first variable must be a true variable, while the second can be either a variable or a constant.
The possible comparison operations are:
•Equality.
•Inequality.
•Less than.
•Less than or equal to.
•Greater than.
•Greater than or equal to.
The representation in the IEC 61131-3 standard is represented as follows:
Input operands can be of type BYTE, WORD, DWORD, INT, DINT, or REAL. The output operand will always be a variable of type BOOL.
Table 2 below shows the comparison operations used for the PLCs: Simatic, Telemecanique, and Allen Bradley.
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