Industrial Engineer · phase 1 of 16 · noun

I/O Module

Module that interfaces the PLC with discrete or analog field signals.

The Explain card

Plain English
An I/O module is the card that connects real wires to the controller. It turns a voltage on a terminal into a bit the program can read, or a bit in the program into a voltage on a terminal.
Example
A sixteen point discrete input card takes sixteen sensors and pushbuttons. A four channel analog output card sends four speed commands to four drives.
Why it matters
The module type sets what the wiring must look like, so picking a sinking card for sourcing sensors means a rebuild of the panel drawings. Its channel count also sets how much of the machine one card can take down.
Hook
The program stops at the module and the plant starts.

Word knowledge

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

In a sentence

On the ControlLogix rack the I/O Module in slot 3 reads sixteen 24 V DC photo-eye inputs from the infeed conveyor.

Why these words
  • I/O English computing slash-pair of input and output, from in + put and out + put marks the traffic half, so the phrase is about what moves rather than the box it lives in
  • module Latin modulus, small measure, diminutive of modus, measure names the removable unit, turning that traffic into a card a technician can seat in a slot
Where it came from
Origin
English computing compound from the slash pairing of input and output (in + put, out + put) and Latin modulus, a small measure
Entered the language
1970s
What changed
Input and output first named the acts of putting in and taking out, then the data a computer received and produced. 1950s computing wrote the pair as I/O. Module had meant a small architectural measure, then a plug-in electronics block. PLC catalogs of the 1970s set the two words on the slot name still printed on a rack drawing.
How it is spelled
Pattern
I/O writes two capitals with a slash and no spaces, as A/C and R/W do
Pattern
Latin -ulus yields English -ule, so module sits with capsule and globule
Breaks the pattern
I/O keeps a slash and two capitals even mid-sentence, never IO, I-O, or i/o
Breaks the pattern
the phrase stays two tokens; I/O-Module is a drawing error

Spelled like

  • A/C
  • R/W
  • capsule
  • globule
Broken into chunks
  • I/O
    • A/C
    • R/W
    • I/P
  • put
    • input
    • output
    • throughput
  • mod
    • mode
    • modify
    • modest
  • ule
    • capsule
    • globule
    • granule
What it sits beside

Same subject

Same shape

Rack modules

I/O family

Slash pairings

  • A/C
  • R/W
  • I/P

Where it sits in the deck

Phase 1: PLC Controller Hardware

The box itself, from processor and rack to the modules that plug into it, because nothing else in the deck lands until you know what a PLC physically is.

Neighbours in this phase