For water applications, two technologies dominate: the YYUS ultrasonic series and the YYEM electromagnetic series. Both are excellent — but they win in different situations.
An electromagnetic flow meter requires the fluid to be electrically conductive (≥5 µS/cm) and measures the voltage induced as the conductive fluid passes through a magnetic field. An ultrasonic meter measures the transit-time difference of sound pulses — it does not care about conductivity, which is exactly why it also works on demineralized water, oils and glycol solutions.
A YYEM inline electromagnetic meter costs more to install on large diameters, but its ±0.5% accuracy holds for decades with zero maintenance. A YYUS clamp-on ultrasonic meter installs on a live line in under an hour with no pipe cutting — unbeatable for retrofits, temporary surveys and large DN pipes. Its accuracy of ±1.0% (±0.5% inline) depends on pipe conditions, so liner buildup and installation geometry matter more than for the YYEM.
Choose YYEM electromagnetic when: the fluid is conductive, accuracy and totalizer integrity are critical, and the meter will stay installed for its full life. Choose YYUS ultrasonic when: the pipe is large (DN300 and above), cutting the pipe is impractical, the fluid is non-conductive, or the measurement is temporary or portable. Many YOYI customers run both — YYEM at revenue points and YYUS for surveys and balancing.
Still unsure? Send us your line data and we will model both options with lifecycle costs, free of charge.