The radar tank level gauge can emit high-frequency microwaves that propagate along the steel rod. Due to encountering the measured medium, the dielectric constant undergoes a sudden change, causing reflection. The time interval between the emitted pulse and the reflected pulse is proportional to the distance of the measured medium. Meanwhile, guided wave radar can also measure the interface between two different media, fully utilizing the difference in dielectric constant of the media. But the measurement condition is that the upper layer medium is non-conductive, or its dielectric constant is more than 10 times smaller than that of the lower layer medium.

The high-frequency microwave pulse emitted by the radar tank level gauge propagates along the detection component (steel cable or steel rod) and encounters the measured medium. Due to a sudden change in dielectric constant, it causes reflection, and a portion of the pulse energy is reflected back. The time interval between the emitted pulse and the reflected pulse is proportional to the distance of the measured medium. Thus, the distance to the surface of the measured medium at the top of the detection component can be calculated, and the total height of the measured container is a known number, which can further determine the level height of the medium.

Radar tank level gauges have the advantages of low maintenance, high performance, high accuracy, high reliability, and long service life. Compared with contact instruments such as capacitors and heavy hammers, it has unparalleled advantages. The transmission of microwave signals is not affected by the atmosphere, so it can meet the requirements of harsh environments such as volatile gases, high temperature, high pressure, steam, vacuum, and high dust during the process.