What is the principle of the weather forecast bottle?

The principle is actually very simple, just a simple barometer, but it can only be qualitative, not quantitative. A certain amount of liquid is injected into the bottle, and then a certain amount of air is left. At this time, the pressure between the air in the bottle and the two liquid levels is balanced, and the nearby pipeline is connected with the outside air, so when the liquid level is stable, the liquid level pressure in the bottle and the pipeline is certain. As we all know, if the weather is going to get worse and the air pressure will drop, the pressure on the liquid level in the tube will decrease, and the pressure of the air in the bottle will push the liquid surface outward, which means that the liquid level in the tube will rise, and vice versa. Therefore, we can only consider qualitatively whether the air pressure has dropped or increased. The impact on the weather can only be used as a reference. In addition, this kind of weather forecast bottle has an inevitable problem about temperature. Because there is air in the bottle instead of vacuum, it is assumed that the air pressure is constant, the temperature drops and the liquid level at the opening drops, and vice versa. A real mercury barometer is a vacuum in a tube and is insensitive to temperature. thank you