manometer

manometri, painemittari An instrument to measure pressure in a fluid, especially a double-legged liquid column gauge used to measure the difference in the pressures of two fluids.
1872, The American Journal of Science

As soon as the manometer of the pump indicated the maximum of rarification, the apparatus was inclined (..)

Pökler helped in working out the Halbmodelle solution: bisecting the model lengthwise and mounting it flat-side to the wall of the test chamber, bringing the tubes through that way to all the manometers outside.