In tidal river sections, backflow drainage, or pump station discharge scenarios, the direction of water flow may reverse. Lanjing Technology Handheld Radio Wave Current MeterDoppler shift symbol discrimination+spectral symmetry analysisAchieve within a range of ± 20 m/sBidirectional automatic meteringNo user preset flow direction is required. .

In physical principle, when the water flow moves towards the radar, the echo frequency increases (positive frequency shift); When moving away, the frequency decreases (negative frequency shift). The device determines the symbol based on the peak position of the frequency spectrum output by FFT:

• If the main peak is located in the positive frequency range → the flow direction is "upstream";

• If the main peak is located in the negative frequency range and flows downstream.

However, in practice, turbulence and wind waves may lead to spectral broadening or even double peaks. Therefore, the system introducesweighted centroid algorithm：

1. Window smoothing of spectral amplitude;

2. Calculate the weighted average of frequency shiftfˉ=∑Ai∑Aifi；

3. according tofˉDetermine the positive or negative net flow direction.

Meanwhile, the software interfaceArrow icon+textClearly display the direction (such as "→ downstream 3.2 m/s") to avoid misreading. A drainage station in a coastal city monitored multiple instances of water backflow during typhoons, and the equipment accurately recorded 5 flow direction switching processes. The data was used to optimize pump station scheduling strategies.

The handheld radio current meter, with its triple mechanism of "physical direction determination+algorithm anti-interference+human-machine directional display", makes bidirectional measurement no longer an exclusive function of high-end devices, but a practical ability for grassroots emergency response.