Comprehensive Manual70
© 2018 Nortek AS
in the Probe Check section.
3.1.5 Test Recorder Function (Vector)
You can test the recorder with the same set-up as above.
1) Start data collection with "Test" followed by "Start With Recorder".
2) Write a name to use for the file you will record internally.
3) After a few minutes, stop the data collection.
4) Retrieve your data by clicking "Deployment" followed by "Recorder Data Retrieval".
5) Convert it to ASCII by clicking "Deployment" followed by "Data Conversion".
6) Review the collected data with an ASCII text editor (i.e. Notepad).
If you leave the instrument collecting data, it will continue to run until the batteries are dead. Always
make sure to stop data collection when testing is complete.
It is a good routine always to start a new deployment with an Empty Memory. Before you erase the
recorder, make sure that you have transferred all the data you want to retain to your computer and
that the data is in good shape. Then click Deployment > Erase Recorder.
Note: The maximum number of files that can be stored in the File Allocation Table (FAT) is 31 on all
Nortek instruments. The "Syslog" takes one spot, so the maximum number of files with
measurements is 30.
3.1.6 Battery degaussing
All fasteners and hardware are non-magnetic and the magnetic signature of the internal electric
components is low. The exception is the alkaline battery pack. Therefore, the batteries are
degaussed before sending them, and also recommend the user to degauss the batteries before
using them.
The calibration routine will compensate for magnetic masses whose field strength, and orientation
relative to the compass, do not change. If the field produced by a magnetic source close to the
compass changes significantly over the course of the deployment, heading errors may be the result.
There is no need to degauss Lithium batteries.
3.2 Customer Calibration
All instruments have what we call head matrices that are unique; it describes the geometry of the
sensor probe, or the transducer orientation to be more specific. The matrices are computed during
the velocity calibration done during production. As long as the sensor probe are not physically
deformed, the head matrices will, consequently, remain the same. Further, what is measured by the
sensor is the change in frequency from the acoustic pulses sent out through the water to those
being reflected back. In other words, a slight change in center frequency will not affect the measured
frequency shift, or the Doppler shift, which is entirely depending on the velocity of particles in the
water. Therefore the sensors never need to be re-calibrated for current speed and direction, unless
they are physically deformed.
3.2.1 Compass Calibration (Vector)
Each compass has been calibrated at the factory to quantify the characteristic response of the
individual components and of the system as a whole. When it leaves the factory, each system can
measure its tilt and the direction of its magnetic field vector accurately, anywhere in the world.
However, users disturb the magnetic field near the instrument when they deploy. Adding a battery
pack and mounting the instrument with deployment hardware adds magnetic materials that change
the magnetic field measured by the instrument. The compass calibration procedure quantifies this
magnetic disturbance, and the instrument's compass algorithm then corrects for it to obtain accurate
heading.
The user should perform a compass calibration just prior to deployment to correct for the introduction
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