Industrial Engineer · phase 4 of 16 · noun

Counter (CTU, CTD)

Functions that count rising events upward or downward and expose completion status.

The Explain card

Plain English: A counter adds one on each rising edge of its input, or subtracts one for the down version, and sets its done bit when the count reaches the preset. A reset puts it back to zero.
Example: A CTU counts bottles past a photo eye and its done bit signals a full case at twelve. A CTD starts at twelve and counts down to zero for the same job from the other end.
Why it matters: Counters count edges, so a sensor that chatters counts extra and a sensor held on counts once. Pair them with a filtered input and a one shot, and reset them somewhere deliberate.
Hook: Every rising edge is another one.

How the word is built, where it came from, and what it sits beside in memory.

In a sentence

A CTU Counter in the packaging PLC advances when the photoeye detects each carton and energizes the case-packer output at twelve.

How it is built

Where it came from

Origin: Middle English counter, formed from count and -er; count came through Old French conter from Latin computare
Entered the language: 14th century
What changed: The word moved from a person who reckons totals to mechanical and electronic tallying devices, then to PLC function blocks.

How it is spelled

Pattern: The suffix -er attaches directly to a verb to name an agent or device.
Pattern: The letter pair ou represents the /aʊ/ sound before nt.

Spelled like

Broken into chunks

What it sits beside

Same subject

Same shape

IEC 61131-3 counter function blocks

PLC state values

Phase 4: PLC Memory, Tags, and Instructions

The data a program moves and the instructions that move it, from a single true or false value up to a structured array.