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Selection & LimitingBeginnerIEC 61131-3

MIN (Minimum Selection)

Returns the smaller of two or more input values.

The MIN function returns the smaller of two (or more) input values. It is used for low-select control strategies from redundant sensors, implementing output ceilings, finding minimum values in process data, and conservative safety-oriented value selection.

Parameters

Inputs

NameTypeDescription
IN1ANY_NUMFirst value
IN2ANY_NUMSecond value

Outputs

NameTypeDescription
OUTANY_NUMMinimum value (smaller of inputs)

Ladder Logic Example

// Ladder Logic - MIN (Low-Select)
//
// |----[MIN]----|
// | IN1: Sensor_1        |
// | IN2: Sensor_2        |
// | OUT: Lowest_Reading   |

Structured Text Example

// Low-select from redundant sensors
Lowest_Pressure := MIN(Sensor_1, Sensor_2);

// Cap output to maximum
Capped_Output := MIN(Calculated_Output, Max_Allowed);

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Platform-Specific Implementation

S

Siemens (TIA Portal)

Use MIN instruction in TIA Portal SCL. In LAD/FBD, use comparison with MOVE.

AB

Allen-Bradley (Studio 5000)

No direct MIN; implement with LES comparison and MOV.

C

CODESYS

Use MIN() function in ST.

Common Applications

  • Low-select from redundant sensors
  • Output ceiling enforcement
  • Conservative value selection
  • Minimum inventory tracking
  • Safety-oriented value selection

Frequently Asked Questions

What is MIN (Minimum Selection) in PLC programming?

Returns the smaller of two or more input values. The MIN function returns the smaller of two (or more) input values. It is used for low-select control strategies from redundant sensors, implementing output ceilings, finding minimum values in process data, and conservative safety-oriented value selection.

What are common applications of MIN (Minimum Selection)?

MIN (Minimum Selection) is commonly used for: Low-select from redundant sensors, Output ceiling enforcement, Conservative value selection, Minimum inventory tracking, Safety-oriented value selection.

How do I use MIN (Minimum Selection) in different PLC platforms?

Siemens: Use MIN instruction in TIA Portal SCL. In LAD/FBD, use comparison with MOVE. Allen-Bradley: No direct MIN; implement with LES comparison and MOV. CODESYS: Use MIN() function in ST.

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