The DFX ultrasonic Doppler flow meter measures flows of liquids containing suspended particles or aerated liquids. Used with the DT9 clamp-on, non-intrusive transducers, the meter is suitable for sewage and mud slurries and can be used on most pipes constructed from metal or plastic. The DT9 transducer for the DFX meter is rated to Type 6 (IP67) and has the ability to work with temperatures up to 194° F (90° C).
Successful application of Doppler ultrasonic flow meters relies on three physical constraints:
The liquid flowing within the pipe must contain 100 ppm of useful sonic-suspended reflectors. Dissolved solids do not generate reflections and are not relevant.
A significant portion of the ultrasound energy generated by the transducer must reach the sonic reflectors. The ultrasonic transducer must be acoustically coupled to the outside of a pipe (using grease or RTV couplant) and the pipe must permit ultrasound to pass without significant attenuation. Most pipes constructed of solid, homogenous materials meet this qualification. Pipes that cause application difficulty include concrete pressure pipes, wood stave pipes, Teflon®-lined pipes, and fiberglass reinforced pipes.
The pipe must be completely filled with liquid when measurements are made. The DFX microprocessor assumes that the pipe is completely full when it calculates the flow rate. The use of partially-filled pipes may result in inaccurate readings.