The external liquid level switch can easily monitor or control the liquid level. The external liquid level switch is mainly used to monitor the liquid level of the storage tank, realize the upper and lower limit alarm or monitor whether there is medium in the pipeline (dry state protection). It can be applied to the liquid level process control of medicine, petroleum, chemical industry, electric power, food and other industries.

At present, there are ultrasonic wave and sonar wave in the external type. The high-frequency ultrasonic pulse generated by its sensor (probe) can pass through the container wall. This pulse will propagate in the container wall and liquid and will be reflected back.

Through the detection and calculation of this reflection characteristic, it can judge whether there is liquid in the container at the monitoring point. At the same time, the liquid level controller can output relay signals to the subsequent electrical appliances or other equipment, so as to monitor or control the liquid level. The externally attached liquid level switch can be actively adjusted, easy to operate and install, safe and reliable, free from repair, non-toxic and environmental protection. It has resistance to sewage and is widely used in domestic, factory and mine pools, oil, acid and alkali pools, barrels, tanks, irrigation and other containers.