Definition
A wire mesh element placed between the cathode and the plate (anode) inside a vacuum tube. A small voltage applied to the control grid regulates the much larger flow of electrons from cathode to plate, allowing the tube to amplify or switch electrical signals.
Plain English
A small wire screen inside an old-style vacuum tube. By changing the voltage on this screen, you control how much current flows through the tube, which is how the tube boosts or switches a signal.
Context Anchor
Seen in discussions of older aircraft radios, electronic equipment, and basic aircraft electrical theory.
Derivation
From 'control' (to regulate) and 'grid' (a mesh or framework of crossed wires). The name describes exactly what it is: a wire mesh that controls electron flow.
Why Pilots Care
Most modern aircraft use solid-state electronics rather than vacuum tubes, but the term may still appear in older aircraft equipment manuals or basic electronics study material.
Analogy
Think of it like the nozzle on a garden hose. The water pressure from the tap is large, but a small twist of the nozzle controls how much actually gets through. The control grid is that small adjustment that governs a much bigger flow.
Intuition Check
A control grid is not a navigation grid or a flight control surface. Here, “control” means controlling electrical flow inside an electronic tube.
Example Sentence 1
When troubleshooting the older transmitter, the technician checked the control grid voltage to see why the tube was not amplifying properly.
Example Sentence 2
A shorted control grid can cause the tube to draw excessive current and overheat.