Tricorder are basically hand-held sensor package. In variants from 2350s to 2379 it was flip-up device, first picture above. Second picture shows its 2379 incarnation.
2360's and 2370's
Aside from scanning environment, tricoder is able to record time trials, play holographic messages, and also has intengrated universal translator. It is also able to be set on passive scan, or continuous scan, recording data even when stored up. It is also capable of being linked to other units, even non-Starfleet ones.
There is also medical version, optimized to scan individuals. It also can be configured to briefly disrupt forcefields, and had detachable hand scanner.
2370's
This unit was similar to previous version in appearance and functions; it could function even undrewater or in hostile environments such as planets suffering nuclear winter, or in temperatures up to 500 K.
Medical version had same modifications as previous medical version.
2379
In 2379 we have final version of Starfleet tricoder (lower picture). It is radical departure from previous models of tricoder, no longer having flip-up controls, instead being similar to PADD, and having touchscreen interface
