A radar water level meter is a kind of non-contact measurement instrument, which is not affected by water flow rate when measuring. Temperature gradient, an accurate and reliable measurement, so it is widely used in the water conservancy industry. But the radar water level meter will also have some problems, there will be some interference factors that make the radar water level meter measurement not so accurate, and there are errors, in the end how to distinguish the interference, this problem has also become some of the level meter industry problems.
We refer to the radar water level meter interference problem as the radar antenna beam width range can only measure the distance of the measured object, and can not distinguish whether the measured object is the water surface. When other objects enter the radar measurement range, it will affect the measurement results, and when the installation height is high, the radar measurement range of the large riverbed is exposed. In this case, it is impossible to distinguish between the riverbed and the water surface, and measurement errors are easy occur.
For this kind of problem, how should we distinguish them? According to the principle of radar ranging, when there are multiple objects within the measurement range of the radar water level meter, that is, when there are interfering objects in the measurement range, the radar water level meter will not be able to distinguish between the water surface and interfering objects.
The general method used by radar water level meters is to select the signal with the highest reflected signal strength or the closest signal to calculate the distance so that the calculated water level will have errors. Therefore, some experts have proposed a method that can distinguish the water surface from other interfering objects, which can effectively solve the error caused by the interfering objects entering the radar measurement range.
Some experts do a test, using 77GHz radar water level meter, the maximum continuous sweep bandwidth of 4GHz, medium frequency signal after fast Fourier transform processing, its resolution can reach 3.75cm, that is to say, the minimum distance to distinguish two objects is 3.75cm using fast Fourier transform of the radar measurement range of the measured objects for initial detection, to determine the number of measured objects. Assuming that the number of measured objects is 1, the accuracy of the measured distance is further improved.
Assuming that the number of measured objects is greater than 1, it is necessary to determine whether the measured object is the water surface and then improve the accuracy of the measured distance. Mainly from these aspects to distinguish, see whether, in motion, the general water surface is not static, there will be fluctuations, interference with the measurement of the object is mostly solid, the surface does not fluctuate. Secondly, observe the difference in reflectivity, generally speaking, the reflectivity of the water surface will be higher than other objects. Finally, you can also pass the periodicity of the movement, the fluctuations of the water surface have a certain periodicity.
The above methods are able to distinguish the interfering objects encountered when measuring radar water level meter, but this is also constructive several theoretical method proposed by experts, I believe that slowly through the continuous progress of technology, this problem will definitely be solved