Which type of instrument is suitable for measuring the flow rate of low-flow, low-pressure air?
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Which type of instrument is suitable for measuring the flow rate of low-flow, low-pressure air? Orifice plate? Vortex street? Still a internal cone flow meter? Output a 4-20mA signal.
Air itself is easily compressible and non-conductive. Therefore, especially when it comes to controlling low flow rates, my suggestion is to reduce the pipe diameter in order to increase the flow velocity. Then, use a float-type flow meter or a turbine flow meter. If you want more accurate flow measurement, you can contact Rehe Croni in Chengde {Köln, Germany} to see if they have flow meters that meet your requirements. . . EMERSON BROOKS also produces. . .
The flow meters you mentioned all have limitations when measuring low flow rates. Orifice plates and V-cones determine the flow rate by measuring the pressure difference before and after throttling, and then performing calculations such as taking the square root. Vortex flow meters are also limited by the flow velocity; it may not be possible to determine the number of pulses generated. I think target flow meters might be a better option.
Thermal diffusion flowmeters (such as the ST98 produced by Acher in the United States) can meet your requirements; they are widely used in our power plants and perform very well.
It’s a thermal gas mass flow meter, but it doesn’t work when the temperature is high.
Why not try EJA’s built-in orifice plate differential pressure transmitter?
I think when people ask questions, they should include the process conditions as well, which will help everyone discuss the issues better!
The original poster mentioned low-flow situations; if the accuracy requirements aren’t very high, a float/rotor flow meter will suffice. It can provide an analog output and is not expensive either. For higher precision, use a turbine, or a thermal mass flow meter – though the latter is more expensive.
The V-cone is expensive, and it is not recommended for ordinary use
Thermal gas mass flow meter – best for low flow rates, low pressure, and normal temperatures