PTFS-IR2223D level sensor is non-contact type, it is used for tube. The principle is infrared, output signal is analog. When there is no water, the sensor outputs low voltage value; When there is water, the sensor outputs a high voltage signal. The photoelectric liquid level switch uses the principle of optical reflection to measure, the performance of level sensor will be affected when it is exposed to direct sunlight or other infrared interference. This sensor have an cover already to avoid it.