Operating Principle:

Mercury barometers measure atmospheric pressure by balancing the weight of a column of mercury in a sealed tube against the atmospheric pressure. The height of the mercury column corresponds to the atmospheric pressure. 

• Advantage: It is a simple concept and easy to use.

• Disadvantage: Difficult to automate and requires manual reading  

• Uncertainty: Measurement errors and produced if the instrument is not vertical

Operating Principle:

Aneroid barometers consist of two circular disks and function with a mechanism which pushes air down on a metal capsule with a spring. As pressure changes, the disks flex and change their relative spacing. It is sensed by a mechanical or electrical element and transmitted to a transducer. 

• Advantage: It is compact and does not require gravity correction.

• Disadvantage: The material drifts easily with time

• Uncertainty: Dynamic wind causes exposure error in the measurements.

Operating Principle: 

Hypsometers contain a pressure sensor that examines the temperature at which water boils. Since water boils at different temperatures based on pressure, the pressure variable can also be inferred.

• Advantage: It is compact and portable.

• Disadvantage: Not as precise since pressure is not measured directly, so liquid impurities or environmental factors can skew measurements

• Uncertainty: Altitude can affect the measurements and also affect the boiling point of water, making calibration necessary to avoid uncertainties