Electromagnetic synthemometer

From Memory Alpha, the free Star Trek reference

An electromagnetic synthemometer was a diagnostic device from the mid-24th century. This hand tool measured the rate of electromagnetic activity of a mechanical device. Ratings were either positive or negative with positive being a good result.

In 2364, a technician aboard the USS Enterprise-D was using this tool in the re-assembly of Lore. (TNG: "Datalore")