Mass spectrometer
A mass spectrometer was a device invented in the 20th century on Earth that was still used in the 24th century aboard Federation starships, and that could measure the mass-to-charge ratio of ions.

When Doctor Beverly Crusher was caught in a warp bubble created by her son, she imagined Geordi La Forge running a mass spectrometer on all particulates in sickbay where she saw an energy vortex, all to no avail. ()

When the the dilithium chamber hatch aboard the  exploded in 2367, La Forge and Data did mass spectrometer readings of the remains of the hatch to see if a chemical explosive was used, but did not find anything suspicious. 

They later, by means of a microtomographic analysis of the dilithium chamber and the hatch mounting, detected sub-micron fractures in the metal casing, a breakdown in the atomic cohesive structure. This meant that neutron fatigue caused the explosion, not sabotage by the Klingon exobiologist J'Dan, as was originally suspected. ()

In 2369, while searching for a cure for the aphasia virus, Dr. Julian Bashir performed a mass spectrometry analysis on a patient's tissue, which revealed a slight genetic abnormality. ()

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Engineering tools
Medical equipment