Nortek Vector Comprehensive Manual

Also see for Vector: Quick start guide

Contents

Nortek Vector Comprehensive Manual Manual pdf 31 page image

Using a Velocimeter 31© 2018 Nortek ASIn a situation where tilt (and therefore heading) values are incorrect due to the instrument and probenot being aligned the XYZ and Beam coordinates are still valid. XYZ and Beam velocity data aregathered with respect to the probe head only.Figure: Orientation of Vector Cable ProbeSpecial consideration must be taken when using a Vector with a cabled transducer array (opposedto the firmly attached stem type). For the cabled type, it is critical that during deployment theinstrument’s array relative to its body (cylinder) is the same as it is with the Vector with the stem.This is because the internal tilt sensor determines up or down, and ultimately ensures that thecorrect coordinate system is used for the directional estimates.2.1.8 Measuring WavesFor readers interested in information about wave measurements in general it is recommended to takea look in the Comprehensive Manual - ADCP, as this manual covers this subject in detail. In thismanual it is focused on how wave estimates can be retrieved by using a Vector.Waves on the ocean surface are clear to us all, however less obvious are the subsurface dynamicsgenerated by these waves. Beneath the surface, waves generate an orbital motion as they pass by apoint (indicated in the figure below). The motion associated with the waves penetrates down into thewater column. Additionally there is also dynamic pressure that is associated with the combinedeffect of the vertical acceleration and the change with depth of the water column. The ability tomeasure these dynamics below the surface makes it possible to interpret the waves on the surfaceand therefore provides the means to estimate many of the wave parameters that are commonly usedto describe a sea state, such as height, period, and direction.The name "PUV" itself is a description of the method as it is an abbreviation of the three quantitiesmeasured: Pressure and the two horizontal components of the wave’s orbital velocity, U and V.These measurements are made at the instrument’s deployment depth and because they are co-located at the same point, this is referred to as a “triplet” measurement.