Video Description: The video has a syringe needle to leak, the video used a longer tube, is to simulate a sealed cavity, the pressure gauge in the video set the lower limit of -0.03Mpa, when Below this pressure value, the pump stops working, when the pressure is higher than the pressure, the pump began to work, the stability of the pressure with the degree of leakage and the need to take the negative pressure of the volume of the cavity, the faster the leakage , The greater the range of pressure fluctuations, and vice versa becomes smaller. The larger the volume of the chamber, the smaller the pressure fluctuation range, and vice versa.