Barometers are used to measure pressure.
It measures atmospheric pressure.
Maybe you mean what does a mercury barometer measure. In which case the answer is atmospheric pressure.
A barometer is used to measure air pressure. It measures the atmospheric pressure using air, mercury, or water and will be shown as inches of mercury or millibars.
Usually no difference at all. They can both move a pointer around a circular scale. The scale can be calibrated in both Inches of Mercury (InHg) or Millbars (Mb). An aneroid system can lend itself more easily to a digital display.
A thermometer measures temperature - most are now electric but they used to have alcohol or mercury in them. A barometer measures air pressure - they are now electric but used to have air in them (in a bellows with a spring).
A mercury barometer is a device that measures air pressure. The key component that distinguishes it from other barometers is the metal mercury.
A mercury barometer.
anaeriod barometer and a mercury barometer
A mercury barometer is a 1 meter long glass tube with the top sealed and turned upside down in a bath of mercury the pressure on the surface of the bath of mercury lifts the level of the mercury in the tube dependent on atmospheric pressure.
otherwise know as a barometer and it measures air pressure in newtons
Mercury barometer precaution
Mercury
A Barometer measures atmospheric pressure.