A liquid sensor system can detect whether liquid is present at a location within a tank or other container, such as an aircraft fuel tank. The system can include a sensor that has a heated negative temperature coefficient (NTC) element and a temperature compensator element. The sensor may be located within the tank. The elements can be polarized by voltages from separate voltage sources. The voltages can be compared to detect a presence or level of liquid within the tank. Only two wires may be needed to connect the sensor with components outside the tank. The system may be able to detect liquid using less than twenty five milliamps and a sensor temperature that is less than two hundred degrees Celsius.