The tricorder is a portable device that scans, analyzes and records data, the indispensable companion of Starfleet officers on away missions since the 23rd century.
The tricorder takes its name from its three primary functions of sensing, computing and recording. It can detect life signs, analyze the composition of materials and the atmosphere, read energy readings, and store what it finds for later study.
In the era of Captain Kirk, tricorders were carried on shoulder straps, and Spock's was rarely far from his side. Later models became smaller and were held in the hand, and variants were made for different specialties, including scientific, engineering and medical versions.
Tricorders are one of the defining tools of Star Trek exploration. Landing parties rely on them to assess unknown worlds, engineers use them to diagnose malfunctions, and doctors rely on medical models to examine patients far from a sickbay, while countless plots have hinged on readings that did not add up.