Definition
A method of representing information using a continuously variable physical quantity, such as the position of a needle, the voltage in a circuit, or the level of liquid in a tube, where the quantity directly corresponds to the value being measured.
Plain English
An analog instrument or signal shows information by smooth, continuous change rather than by discrete numbers. A moving needle or a rising column of liquid is analog because it varies in step with what it's measuring.
Context Anchor
Seen when comparing cockpit gauges, instrument displays, and aircraft electrical signals.
Derivation
From the Greek 'analogos,' meaning 'proportionate' or 'corresponding.' The idea is that one thing varies in proportion to another -- a needle's position is analogous to the pressure or speed it represents.
Why Pilots Care
Analog instruments let pilots see trends and rates of change instantly without reading digits.
Analogy
An analog gauge is like a dimmer knob for a light: it can move smoothly through many positions, not just jump from one fixed setting to another.
Intuition Check
Analog does not mean “old” or “less accurate” by itself. Here it means the information changes smoothly in proportion to the thing being measured.
Example Sentence 1
The airspeed indicator in the trainer is an analog gauge, with a needle sweeping around a numbered dial.
Example Sentence 2
Many pilots still prefer the analog vertical speed indicator because small changes are easier to detect at a glance.