A device that detects or senses a physical quantity, substance, or condition. Used in technical and everyday contexts.
A smoke detector is built into the fire alarm.
This gas detector can also detect carbon monoxide.
探知機 emphasizes searching or locating (e.g., radar, sonar), whereas 検知器 focuses on detection of presence or change.
Compound of 検知 (detection) + 器 (device, instrument). The exact historical derivation is uncertain, but the word follows a common technical naming pattern.