One group used experimental equipment such as pressure gauge to "explore the characteristics of liquid internal pressure". Please answer the following questions. (1) The pressure gauge compares the li

One group used experimental equipment such as pressure gauge to "explore the characteristics of liquid internal pressure". Please answer the following questions. (1) The pressure gauge compares the liquids on both sides of the U-shaped tube. In the experiment (1), the water pressure at the probe was judged by observing the height difference between the two sides of the U-shaped tube.

(2) If the air tightness of the pressure gauge is not good, it means that the gas in the hose is connected with the atmosphere, which is equal to the atmospheric pressure. When the rubber film is compressed, the gas pressure in the hose will not change, and the liquid level in the U-shaped pipe will not be different.

(3) After the pressure gauge is adjusted normally, fix the probe at a certain fixed depth, rotate the rubber surface in different directions such as up and down, and observe the liquid level difference of the U-shaped pipe. This step explores the relationship between liquid pressures in all directions at the same depth;

(4) Immerse the probe into water with different depths, as shown in Figure B, and observe the height difference of the liquid level in the U-shaped tube, and find that HA < HB < HC. Conclusion: In the same liquid, the liquid pressure increases with the increase of depth.

So the answer is: (1) height difference; b； (2) The air tightness of the pressure gauge is not good; (3) the relationship between the liquid pressures in all directions at the same depth; (4) In the same liquid, the liquid pressure increases with the depth.