In practical use, we have found that radar waves are a special form of electromagnetic waves, and radar level gauges utilize the special properties of radar waves to measure liquid levels. The physical properties of radar waves are similar to visible light, with a propagation speed equivalent to the speed of light. Its frequency is between 300MHz-3000GHz. Radar waves can penetrate interference sources such as space vapor and dust, and are easily reflected when encountering obstacles. The better the conductivity or dielectric constant of the measured medium, the better the reflection effect of the echo output signal. The higher the frequency of the radar wave, the smaller the emission angle, the greater the energy (magnetic flux or field strength) per unit area, and the smaller the attenuation of the wave, the better the measurement effect of the radar level gauge.

The basic principle of radar level gauges is transmission reflection reception. The antenna of the radar transmitter emits a minimum radar output signal of 5.8GHz in the form of a beam. The reflected output signal is still received by the antenna, and the running time of the radar pulse output signal from transmission to reception is proportional to the distance from the transmitter to the surface of the medium and the level of the object.

Radar level gauge is a radar level gauge based on the principle of time domain reflection (TDR). The electromagnetic pulse of the radar level gauge propagates along the steel cable or probe at the speed of light. When it encounters the surface of the measured liquid level, some of the pulses of the radar level gauge are reflected to form echoes and return to the pulse emitting device along the same path. The distance between the emitting device and the surface of the measured liquid level is proportional to the propagation time of the pulses between them, and the liquid level height is calculated.