Doppler ultrasonic flow meters are designed to measure volumetric flow of solids-bearing or aerated liquid within closed conduit ,he pipe line must be full of liquids with a certain of air bubbles or suspended solids .The one could display flow rate and flow totalizer,etc.Also, it is configured with 4-20mA , OCT outputs.Handheld flowmeters are suitable for pipe size ranging from 40mm-4000mm.It could work in many places of opearting temperature -20 to 60 ℃ .It widely used in full filled pipes , such as raw sewage,activated sludge,ground water,pulp ,paper/chemical slurries,drainage and mining recirculation and so forth.