OTT MF pro, Operating Instructions Manual

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Figure 17 Typical profile
1 Depth 2 Velocity
Site selection
A site with the typical profile shape gives the most accurate results. Visual inspection is typically
sufficient to identify problem sites. Use the information in these guidelines to help select the best site.
These guidelines apply to conduit and stream profiles.
• The channel should have as much straight run as possible. If the length of the straight run is
limited, the length upstream from the profile should be two times the downstream length.
• The channel should be free of flow disturbances. The site must not have protruding pipe joints,
sudden changes in diameter, contributing side-streams, outgoing side-streams or obstructions.
Remove all rocks, sediment or other debris from the bottom of the pipe.
• The flow should not have visible swirls, eddies, vortices, back-flow or dead zones.
• Do not select areas immediately downstream from sharp bends or obstructions.
• Do not select areas with converging or diverging flow (approaches to a flume) or vertical drops.
• Do not select areas immediately downstream from sluice gates or places where the channel spills
into a body of stationary water.
Do a velocity calibration
Use this feature to remove a velocity offset if necessary. The velocity offset stays active until the
meter power is switched off.
1. Collect a bucket of water from the water in the profile area. The bucket must be non-metallic and
at least 20.32 cm (8 in.). The water depth must be at least 15.24 cm (6 in.).
2. Put the sensor in the center of the bucket so that it does not touch the sidewall or the bottom of
the bucket.
3. Let the water become still.
4. Let the velocity reading stabilize.
5. Select Zero Velocity.
Wet/Dry threshold
The wet/dry threshold is the trigger point for the meter to know when the sensor is in or out of the
water. This information is important because if the meter does not know that the sensor is under the
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