3.6. Fogging and Evaporation

Radar sensors are generally not affected by fog or regular water evaporation. Measurement performance remains stable under typical environmental conditions.

The exception is in the case of very heavy evaporation, where the concentration of water vapor directly above the surface is extremely high, such as wastewater channels or sewage pipes. In such conditions, the surface velocity measurement may be affected. If strong evaporation is present, the following configuration is recommended (this overrides general alignment guidance):

• Install the instrument so that it measures outgoing flow direction (water flowing away from the radar).

• Enable or configure the sensor to use incoming-only directional filtering.

Evaporation rises vertically upward from the water surface and moves toward the radar. By enabling downstream directional filtering, signals traveling toward the radar (inbound direction) are rejected. In most cases, this effectively eliminates the influence of evaporation on the measurement.