Nortek Vector Comprehensive Manual

Also see for Vector: Quick start guide

Contents

Nortek Vector Comprehensive Manual Manual pdf 35 page image

Using a Velocimeter 35© 2018 Nortek AS2.1.9 Optional IMUNortek offers the Vector with an optional integrated Intertial Motion Unit (IMU). This sensor isintended to help understand how the Vector's own motion influences the measurements. The simpleconfiguration allows one to record motion data simultaneously with the Vector velocity data. The datafrom the IMU sensor are sampled and stored in realtime, so the velocity measurements and themotion and orientation measurements are tightly synchronized. Before continuing; be aware that thedescription below applies for Vectors using firmware/software versions from V3.42/V1.39 and onward.If you use older versions, an update is recommended.Physically, the IMU is incorporated in the Vector by simply using the magnetometer contactinterface. This means the standard tilt and magnetometer are removed and replaced with the IMU.So there is no standard Nortek compass system with the IMU integrated.Note that the use of IMU demands the use of 4GB recorder, due to the amount of data collected.Figure: The IMU sensor replaces the com pass boardThe velocity measurements and the IMU data will be presented in the coordinate system selected.The IMU can be used as an AHRS; since the Vector with IMU can be used in any orientation(horizontally, vertically,..) while simultaneously converting the measured velocities to ENU, - thus afull 3D solution. We also indicate the heading, pitch and roll to the direction the instrument hadduring the measuring period.Note that there is no advanced internal processing as this is left with the end user. The softwaredoes only correct for orientation, it does not manipulate velocity other than transforming it to ENU.Correcting for movement will have to be done as a next processing step by the user, using e.g. deltavelocity/delta angle. But the good news is that the orientation will be correct even when there ismovement.The end user would benefit by understanding the sensor itself. This may be done by visiting theproduct page and looking at the Documentation tab: http://www.microstrain.com/inertial/3DM-GX3-25-OEMThe location of of the IMU is relevant if e.g. removing the affect of mooring vibrations are of interest.The center of the sensor is 16 cm from the end of the endbell where the probe stem is affixed.Figure: Location of IMU relative to stem