Which instrument measures pressure, typically in gas or air systems?

• A. Barometer
• B. Ammeter
• C. Manometer
• D. Thermometer

Answer: (C)

Measuring pressure in gas or air systems is done with a device that translates pressure into a liquid height difference. The manometer fits this purpose best because it directly shows pressure by balancing the gas against a column of liquid; the height change corresponds to the pressure value, and you can read either gauge pressure relative to atmosphere or absolute pressure depending on the setup. Barometers, by contrast, are designed for atmospheric pressure and weather use, not for pressurized gas systems. An ammeter measures electric current, not pressure, and a thermometer measures temperature. So for assessing pressure in gas or air systems, the manometer is the appropriate instrument.