Foam in a flume or weir system can cause no end of problems.  It’s important, therefore, to make sure that you select the right flow meter technology.

Ultrasonic flow meters are particularly susceptible to foaming.  They work by sending a pulse of sound and measuring the time for the echo to return.  When foam is present, the meter receives an echo from the foam itself and not the water’s surface.  As a result, level / flow readings are artificially high.

Bubbler meters and Pressure Transducers are generally better flow meter choices as they sense level from the bottom up (and not the top down like the ultrasonic meter).  Both meters rely on pressure sensors to measure either the amount of force used to expel air (bubbler flow meters) or the amount of water column above the sensor (pressure transducers).  As a result, the light foam at the water’s surface is not a factor in how either flow meter determines the water level.