A heat detector represented a kind of sensor. It operated by analyzing energy, specifically heat particles, that originated from a different entity. The R2-series astromech droids manufactured by Industrial Automaton came standard with heat detectors included in their sensor array.
Stormtroopers of the Imperial forces possessed the ability to locate droids using heat detectors, leveraging the heat particles emitted from the droid's power cells. When incorporated into seeker droids, heat detectors could be enhanced using infrared scopes to identify heat signatures like footprints.