Definition
The process of changing a continuously varying (analog) electrical signal into a series of discrete numerical values (digital data) that a computer or digital system can store, display, or process. The analog input is sampled at regular intervals, and each sample is assigned a numerical value representing its amplitude at that instant.
Plain English
Taking a smooth, continuously changing signal -- like a voltage that rises and falls -- and turning it into numbers a computer can work with. The system measures the signal many times per second and writes down each measurement as a number.
Context Anchor
Seen in avionics, engine monitoring, flight instruments, and any system where a sensor sends information to a computer or digital display.
Derivation
Analog comes from the Greek analogos, meaning 'proportional' -- the signal's voltage is proportional to whatever it's measuring (pressure, temperature, etc.). Digital comes from the Latin digitus, meaning 'finger,' because counting on fingers gave us discrete numbers. Conversion is simply changing one form into another. So the term literally describes turning a 'proportional' signal into 'countable' numbers.
Why Pilots Care
Aircraft computers and displays can only use digital data, so analog-to-digital conversion is required for accurate, noise-resistant processing of flight instrument and engine sensor information.
Analogy
A thermometer with a rising column shows temperature as a smooth change. A digital thermometer samples that change and shows it as numbers, such as 72 or 73 degrees.
Grounding Statement
Aircraft sensors create smooth voltage changes that must become exact numbers before the flight computer can calculate altitude, airspeed, or engine performance.
Intuition Check
Analog-to-digital conversion does not mean simply replacing an old instrument with a new screen. It means translating a changing electrical signal into numbers for electronic use.
Example Sentence 1
The air data computer performs analog-to-digital conversion on the pitot and static pressure signals before sending altitude and airspeed data to the primary flight display.
Example Sentence 2
During preflight, technicians verify that analog-to-digital conversion of the fuel quantity sensor produces stable digital readings on the cockpit display.