Industrial Engineer · phase 2 of 16
AO / Analog Output
Output that sends a continuous command signal such as 4-20 mA or 0-10 V to another device.
The Explain card
- Plain English
- An analog output sends a continuously variable command out of the controller. Instead of on or off it says forty percent, or twelve milliamps, or seven volts.
- Example
- The PID loop for a tank level writes its result to an analog output. That output drives a control valve to whatever opening the loop asks for.
- Why it matters
- Drives, valves and dampers all take their setpoint this way, so a loose analog wire makes a valve drift without any fault appearing. Set the channel's fault state so a lost controller cannot leave the valve at its last command.
- Hook
- The controller's dimmer switch.
Word knowledge
How the word is built, where it came from, and what it sits beside in memory.
In a sentence
Wire the PLC AO channel to the VFD speed-reference terminals, then scale the channel in the controller configuration.
Letter by letter
- A Analog identifies the signal class
- O Output identifies the channel direction
Where it came from
- Origin
- English engineering initialism formed from Analog Output
- Entered the language
- 20th century
- What changed
- The full technical phrase was shortened to AO on drawings, module labels, tag names, and programming documentation.
How it is spelled
- Capitalisation
- Written AO in capitals, including mid-sentence
- Plural and possessive
- Plural AOs; singular possessive AO's; plural possessive AOs'
- Out loud
- Spelled out letter by letter.
Same family
- AI
- DI
- DO
Broken into chunks
-
analog
- analogy
- analogous
-
output
- input
- throughput
Where it sits in the deck
Phase 2: PLC I/O and Field Signals
Where the controller meets the machine: discrete and analog signals, the wiring conventions behind them, and the field devices that send them.
