Ultrasonic time differential method measures flow velocity depending on properties of changes occurring
in ultrasonic radio wave speeds.
  1. The ultrasonic sensor is attached to outside wall of pipe.
2. The ultrasonic sensor is non-contacted with the fluid. Accordingly, there are no problems for corrosion
    and attachment. In addition, since there are no obstacles for fluid flowing, there is no pressure loss.
3. Since turbulent flow gives a great influence to the accuracy, it needs to attach
    straight pipe in upstream and downstream.