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Vortex flow meters is made up of a swirl generator, a detected probe and other relevant electronic circuit. Within the flow meter, as the flow moves across the swirl generator, two rows of alternately changed swirl which is called Karman vortex are generated. On the base of Karman vortex principle, Strouhal gave the relational expression between flow rate and vortex frequency:

  • f = St x V/d
  • f: freqyebct if geberating vortex (Hz)
  • V: average speed of flowing swirl (m/s)
  • Sr: Strouhal number (constant)
These alternately changed swirls then generate a seiries of alternately changed negative pressure and the changed pressure is converted into AC electrical signal through the detected probe. After digital processing, plastic and amplifying process, pulse frequency signal(or standard signal) will be output, which is synchronized and proportional to the swirl.