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In Siemens PLCs, in-range and out-of-range operations are common for monitoring whether an analog or digital value lies within a specified range. These operations are typically implemented using comparison instructions or dedicated function blocks in the Siemens TIA Portal software. Here's a detailed explanation:

In-Range Operation
Definition: Checks if a value falls within a defined range, inclusive of the boundaries.

Logic:

The condition is true when the value is greater than or equal to the lower limit and less than or equal to the upper limit.
Formula:
Result=(Lower Limit ≤ Value) ∧ (Value ≤ Upper Limit)

Implementation in Siemens PLC:

Comparison Instructions: Use (Greater or Equal) and (Less or Equal) operators in a ladder logic or structured control language (SCL) block.
Function Block (e.g., FB): Siemens PLCs may have function blocks for range checking, like LIMIT or custom range-checking blocks.

Applications:
Temperature control to ensure the value stays within safe limits.
Monitoring sensor values like pressure or speed.
Out-of-Range Operation
Definition: Checks if a value is outside a specified range.

Logic:
The condition is true when the value is less than the lower limit or greater than the upper limit.
Formula:
Result=(Value Lower Limit) ∨ (Value Upper Limit)
Implementation in Siemens PLC:

Comparison Instructions: Use (Less Than) and (Greater Than) operators.
Function Block (e.g., FB): Similar to in-range, but inverted logic.

Applications:
Alarming or shutting down equipment when operating conditions exceed limits.
Fault detection in sensor inputs.
Using the LIMIT Instruction in Siemens TIA Portal
Siemens provides a LIMIT instruction that simplifies in-range checks:

Inputs:
IN: The value to check.
LOW: The lower limit.
HIGH: The upper limit.
Outputs:
OUT: Adjusted value clamped within the range (if necessary).
LO: True if below the lower limit.
HI: True if above the upper limit.

Example:

LIMIT(Low := 10, High := 100, In := Sensor Value, Out = Value Clamped);
This block adjusts Sensor Value to be between 10 and 100. Additionally, it sets flags for whether the value was out of range.