Electrode type water level sensor

The invention relates to an electrode type water level sensor which is used in a water heater. The water level sensor is characterized in that a No.1 resistor, a No.2 resistor, a No.3 resistor and a No.4 resistor are connected in series in sequence; the No.4 resistor is electrically connected with a signal input end; the No.1 resistor is electrically connected with a signal output end and a common electrode respectively; a No.1 control circuit is connected with the No.1 resistor in parallel and is electrically connected with a No.1 water level electrode; a No.2 control circuit is connected with a series resistor formed through serial connection of the No.1 resistor and the No.2 resistor in parallel and is electrically connected with a No.2 water level electrode; a No.3 control circuit is connected with a series resistor formed through serial connection of the No.1 resistor, the No.2 resistor and the No.3 resistor in parallel and is electrically connected with a No.3 water level electrode; and a No.4 control c