The “psychometer” described in this article works in the same way as modern polygraph machines. As the article puts it, “the human body’s resistance to an electrical current increased with the increase of the motions.” Skin conductivity, along with blood pressure, pulse, and respiration, can all be indicators that a person is lying.
But the technology is still far from being “perfected so as to be infallible.” You needn’t look hard to find harsh criticism of lie detectors including tips on how to beat one. In an episode of Penn & Teller’s Showtime program Bullshit, they talked to “people whose lives were ruined by faulty lie detector results.”
ELECTRIC MACHINE TO TELL GUILT OF CRIMINALS: If It Is Perfected So As to Be Infallible It Will Make Expert Testimony Unnecessary and May Eliminate Juries in Trials. (PDF)
From September 10, 1911