Mass Spectrometer

A mass spectrometer is a device invented in the 20th century on Earth that is still used in the 24th century aboard Federation starships, and that can 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. (TNG: "Remember Me")

When the the dilithium chamber hatch aboard the USS Enterprise-D 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. (TNG: "The Drumhead")