In the past, the small flow measurement is done by differential pressure type flowmeter,float flow meter,positive displacement flowmeters,turbine flow meters,etc.Now as the new technology development,mass flow meter,ultrasonic flow meters are widely used for small flow measurement of liquid and gas.
As rising of semiconductor manufacturing industry, biological engineering, fine chemical industry,etc,small flow measurement has been requested from the year of 80-90. There is no united definition of small flow ,and small flow rate is usually expressed by small pipe size and small velocity. Customarily, the small size below DN15mm or liquid flow rate below 1L/min or 0.06m3/h or the flow velocity is below 0.1m/s.
Turbine type flow meters have been widely used for small pipe flow measurement,but mechanical flow meters have many disadvantages: moving parts,no sensitive to flow,pressure loss,pollution for liquid,etc.
Magnetic flow meters are also used for small flow measurement.But as small pipes are widely used for ultra-pure water measurement,and magnetic flow meter has a limit of electric conductivity,so magnetic flow meters are not so popular like ultrasonic flow meter and mass flow meters. Meanwhile,comparing with ultrasonic flow meters,magnetic flow meters is not so good to low flow.
Mass flow meter can be used for small pipe flow measurement,but for liquid flow,mass flow meter has a very high price,so at present,ultrasonic flow meter should be the best solution.
Ultrasonic flow meters can be used for DN3mm pipe flow measurement of liquid, and mass flow meter can be used for DN3mm liquid and gas flow measurement.For liquid flow,corolis mass flow meter is used, for gas flow,thermal mass flow meter is introduced.
We have developed DN6mm small ultrasonic flow meters,if you are interested,please feel free to contact us.