What type of level sensor cannot be used when the water body freezes?

The float mechanism operates based on the principle of buoyancy, where a floating object rises and falls with the water level. In situations where the water body freezes, the ice can interfere with the float's ability to move freely. If the water beneath the ice is significantly lower than the ice thickness, the float may become stuck or unable to provide an accurate reading of the actual water level. This characteristic makes float mechanisms less reliable in environments where freezing occurs.

In contrast, other types of sensors, such as ultrasonic and radar sensors, don't physically interact with the water. They measure distance using sound waves or electromagnetic waves, respectively, and can function even when a water body is frozen. Pressure sensors, on the other hand, gauge the pressure at a certain depth and can still operate below the ice, provided they are adequately positioned. Thus, the float mechanism is particularly susceptible to failure in frozen conditions, making it unsuitable for use in such environments.