Subsidence sensing device with liquid replenishing mechanism

A subsidence sensing device comprising:

• multiple liquid storage tanks, each of the liquid storage tanks containing liquid, and the liquid storage tanks connected with each other via communicating tubes;
• multiple level sensors mounted on the liquid storage tanks respectively;
• a liquid feeding tank disposed higher than liquid surfaces of the liquids in the liquid storage tanks and containing feeding liquid;
• an air inlet tube having
• an upper open end protruding into the feeding liquid in the liquid feeding tank;
• and
• a lower open end protruding into the liquid in a corresponding one of the liquid storage tanks;
• and
• a liquid feeding tube having
• an upper open end protruding into the feeding liquid in the liquid feeding tank;
• and
• a lower open end protrudes into the liquid 101 in a corresponding one of the liquid storage tanks;
• wherein the feeding liquid in the liquid feeding tank flows into and fills the air inlet tube and the liquid feeding tube and a length that the liquid feeding tube protrudes in the liquid of the corresponding one of the liquid storage tanks is longer than a length that the air inlet tube protrudes in the liquid of the corresponding one of the liquid storage tanks.