A device that detects physical phenomena such as smoke, heat, or motion. Often used in safety and monitoring contexts.
The fire detector activated and the alarm sounded.
A smoke sensor is installed in this room.
センサー is a more general and common loanword for 'sensor', while 感知装置 is a technical compound often used in formal or industrial contexts.
Compound of 感知 (kanshi, 'detection') and 装置 (sōchi, 'device').