Auto water temperature sensor principle: container of water level sensor, will feel the water level signal to the controller, the controller inside the computer to set the water level of the measured signal and signal comparison, it is concluded that deviation, then according to the nature of the deviation to feed water electric valve "open" "off" instructions, ensure the container to set the water level. After the filling process is complete, the computer in the temperature control unit sends an "on" command to the electric valve that supplies the heat medium, and the system begins to heat the water in the container. At the set temperature. The controller then issued the command to close the valve and cut off the heat source, and the system entered the heat preservation state. In the process of programming, to ensure that the system does not reach the safe water level, the electric control valve of the heat source does not open the valve, so as to avoid the loss of heat and the occurrence of accidents.