Ultrasonic anemometers are unable to make measurements if the sonic path is blocked. The path may become blocked by water that puddles on the lower transducer face or droplets that hang from the upper transducers. Sonic wicks, which come with all sonics, can be placed on the transducers to wick away moisture from the faces of the transducers. Ensure that these wicks are removed during cold conditions to prevent ice from building up around them.