Barometer

A barometer was an meteorological instrument used to measure barometric pressure. Its measurement was in terms of units of millimeters of mercury, or mmHg.

The atmospheric pressure of Taurus II was 70 mmHg. 

Making an analogy to barometric gradients of gas pressure, USS Voyager helmsman Tom Paris joked that Commander Tuvok would have made a good barometer, as his Vulcan physiology was sensitive to neutronic gradients.