What is the working principle of the blowing method for measuring liquid level? What type of containers is it suitable for measuring the liquid level in?

An open container containing a liquid that does not react chemically with air

The principle of using the blow-out method to measure liquid level is to determine the level by achieving equilibrium between gas pressure and hydrostatic pressure (hρg), and it can only be used to measure liquids in open containers.

The hydrostatic principle is used to measure the liquid level in open containers. Using a blow-out type level gauge to measure liquid levels has certain limitations; it is generally only suitable for measuring levels in open-type equipment or in situations where high precision is not required. The process involves compressed air passing through a filter and a pressure reducing valve; depending on the level of the liquid being measured, the air pressure is reduced to a certain value P1. It is then reduced further to P2 via a throttling element (such as a flow control orifice or needle valve), and after that it passes through a rotameter. Finally, the compressed air escapes from the open end at the bottom of the air duct installed in the equipment (with the transmitter connected after the rotameter). When a trace amount of gas escapes from the lower end of the gas conduit, the pressure inside the conduit is almost equal to the liquid seal pressure inside the container. At this point, the pressure reading displayed by the transmitter accurately reflects the liquid level height of the equipment. Its mathematical relationship is H = P/ρ, where H represents the liquid level height, P denotes the pressure at the transmitter, and ρ is the density of the medium being measured in the open-type device. The blowing method for measuring liquid level is mainly used in situations where high requirements, strict control, or high precision are not necessary. In principle, it is a static pressure measurement; it has large errors, consumes air for the instrument which is not energy-efficient, and requires significant maintenance.