What is the best type of flow measuring device in a closed channel to measure solids?

The magnetic flowmeter is particularly well-suited for measuring flow in closed channels containing solids, primarily because it operates based on the principle of electromagnetic induction. This device measures the velocity of conductive liquids as they flow through a magnetic field, and since it doesn't have any moving parts, it can handle slurries or liquids that contain solids without being affected by changes in density or viscosity.

This type of flowmeter is advantageous in wastewater treatment settings because it can provide accurate flow measurements even in the presence of suspended solids, which may interfere with other types of flow measuring devices. For instance, a Venturi meter relies on pressure changes and can be influenced by solid particles, potentially leading to inaccurate measurements. Similarly, a rotameter, which relies on the float position within a tapered tube, may be affected by solids settling or changing the fluid's characteristics. Ultrasonic flowmeters, while effective for clear liquids, can struggle to accurately measure flow when solids are present due to signal absorption or scattering.

In environments where solids are present, the magnetic flowmeter stands out for its reliability and accuracy, making it the best choice among the options listed for measuring flow in closed channels with solids.