… Instruments and apparatus for measuring or checking the flow, level, … gases (for example, flow meters, level gauges, manometers, heat meters), excluding instruments and apparatus of …
Explanatory notes
… 90.26 ‑ Instruments and apparatus for measuring or checking the flow, level, pressure or … These differ from barometers in that the latter measure atmospheric pressure while pressure gauges indicate the … of the electrons with the molecules of the residual gas are attracted towards a negative plate. Thermionic vacuum tubes …