In which method is the height of liquid measured indirectly?

Measuring liquid pressure is an indirect method for determining the height of liquid in a container. This approach is based on the principle that the pressure exerted by a column of liquid is proportional to the height of that liquid. The formula used is ( P = \rho g h ), where ( P ) is the pressure at the bottom of the liquid column, ( \rho ) is the density of the liquid, ( g ) is the acceleration due to gravity, and ( h ) is the height of the liquid.

In this method, a pressure sensor, often a manometer or a transducer, detects the pressure at the bottom of the vessel, which can then be converted into height. This technique is widely used in industrial applications due to its reliability and the fact that it does not require direct contact with the liquid, making it suitable for hazardous or corrosive liquids.

Direct methods, like using a ruler or direct contact sensors, measure the height directly and do not utilize pressure measurements. Ultrasonic measurement also indirectly determines liquid height but does so by using sound waves rather than measuring pressure.