The core element of the velocity meter HM 161.64 is an impeller that is rotated by the flow. The speed of the impeller is proportional to the flow velocity. The flow velocity is read directly from the digital display.
The impeller tube can be moved vertically. A scale indicates the corresponding vertical position of the measurement.
HM 161.64 is mounted on the moveable instrument carrier HM 161.59 so it can be used along the length and width of the experimental section.