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GRT — Greater Than

Category
Compare
Type
Input (condition)
Availability
All platforms

GRT instruction block: Source A Temp reading 72.5, Source B 85, dark because 72.5 is not above 85

Description

Section titled “Description”

GRT (Greater Than) is true when Source A is strictly greater than Source B. It is a condition that writes nothing. Use GRT for a high alarm, an over-temperature cut-out, an “above target” test, or the top edge of a band together with LES. When “equal to” should also count, use GEQ. GRT does not accept STRING operands.

Operands

Section titled “Operands”
Operand Type Format Valid Range Required Description
Source A Any numeric tag, member, element or bit, or a literal Tag, Tag.Member, Tag[n], Tag.bit, or a literal Any resolvable numeric reference Yes The value under test.
Source B Same as Source A Same Any resolvable numeric reference; defaults to 0 Yes The threshold.

Literals may be whole numbers (25, -3, 0x1F) or decimals (72.5). Mixed INT and REAL operands compare as numbers. A BOOL reads as 0 or 1.

Scan Behavior

Section titled “Scan Behavior”

Prescan

Section titled “Prescan”

No state. Evaluates from the current values on the first scan.

Rung-condition-in is false

Section titled “Rung-condition-in is false”

The instruction does not pass continuity. The block still colours by its own result on the canvas.

Rung-condition-in is true

Section titled “Rung-condition-in is true”

Both operands are read. If A is greater than B the instruction conducts; if A is less than or equal to B the rung is false from this point.

Postscan

Section titled “Postscan”

Nothing.

Example

Section titled “Example”

Scenario: A cabinet temperature in degrees. Above 85 a cooling fan runs.

Tags:

  • Temp — Cabinet temperature, REAL
  • Fan — Cooling fan, BOOL

Rung 1:

—[GRT Temp  85]———(OTE Fan)———

Scan 1 — Temp = 72.5. 72.5 is not greater than 85: the block is dark, Fan = 0. Temp is a REAL, so its value line keeps the fraction; the literal 85 was typed as a whole number and compares as one.

Figure 1 — GRT false: Temp reads 72.5 against Source B 85, the block dark, Fan off

Scan 2 — Temp = 91.3. 91.3 is greater than 85: the block lights, Fan = 1.

Figure 2 — GRT true: Temp reads 91.3, the block lit, Fan on

The fan stops the moment Temp falls to 85 or below. For a fan that runs on until the cabinet has cooled further, add hysteresis as described in the Notes.

See Also

Section titled “See Also”
  • GEQ — Greater Than or Equal
  • LES — Less Than (the mirror test)
  • LIM — Limit Test (both edges of a band in one instruction)
  • CMP — Compare by expression
  • Compare Instructions — Category index

Notes

Section titled “Notes”

Hysteresis. Start the fan on GRT Temp 85 with an OTL and stop it on LES Temp 75 with an OTU. The fan then cycles between two temperatures instead of chattering at one.

REAL literals. Type the literal with a decimal point when Source A is a REAL, so the intent is clear on the block face. GRT Temp 85 compares the same way.

Members as operands. GRT TMR[0].ACC 5000 is true once a timer has been running for five seconds, without waiting for its preset.

Applies to LadderIDE >=1.2.2 · Last reviewed 2026-09-11 · Screenshots verified 2026-09-11