Aligning the VEL‑R‑5
For the installation of the VEL‑R‑5 , mounting kits for various installation situations are available (see Assembly sets). The alignment of the VEL‑R‑5 with the flume to be measured is carried out for all flexibly adjustable mounts using the procedure described below. These can basically be divided into flexibly adjustable mounts and fixed mounts. Due to the fixed angle of 45° of the flow velocity sensor mount and the absence of joints, the rigid mounts offer less flexibility in aligning the sensors to the channel than the flexible mounts. However, they are significantly less sensitive to changes in sensor alignment due to the impact of external factors during operation.
Choosing the mounting direction
Regardless of the choice of mounting kit, the first decision to be made is whether the VEL‑R‑5 should be aligned in the direction of flow or against the direction of flow. It is recommended that the VEL‑R‑5 be installed against the direction of flow, as this alignment provides a more accurate measurement result (see Framework conditions for a reliable measurement). If this is not possible due to the installation situation, the VEL‑R‑5 can also be installed in the direction of flow. In this case, the installation direction must be set to "downstream" in the input screen for configuring the data logger linked to the VEL‑R‑5 so that the surface velocity is output with the correct sign.
|
Upstream installation |
Downstream installation |
Taking fall gradients into account
If the channel has a gradient of ≥ 2° , this must be taken into account when determining the angle of attack of the sensor. When installing upstream, the angle between the sensor axis and the horizon must be reduced by the angle of the gradient. When installing downstream, the angle between the sensor axis and the horizon must be increased by the angle of the gradient. This correction ensures that the angle of attack of the sensor relative to the water surface corresponds to the desired angle (e.g. the recommended 45°).
|
Upstream installation |
Downstream installation |
| α | Angle of attack of the sensor relative to the water surface (recommendation: 45°) | β | Gradient of the duct |
Final alignment
The final alignment of the VEL‑R‑5 with the flume to be measured is carried out for all flexibly adjustable mounts using the procedure described in section Flexibly adjustable mounts. When using a fixed mount, the procedure described in section Fixed mounts is to be used.
