Comprehensive Manual112
© 2018 Nortek AS
Sharp peak in the beginning of the plot
Scaling: The graphs grows beyond the screen. Solution: Right-click inside the graph and select
"Scaling" to adjust the range of the Y-axis.
The scaling of the axis can be adjusted in the softw are
5.3.3 Boundaries
In open waters, boundaries are not a concern, but if you want to use the instrument near the bottom
or surface, think about the boundaries when designing the experiment. If one of the beams cross a
hard boundary, whether surface, bottom or wall, velocity data from that beam will be bad. There are
several different ways to improve the situation; one example is to change the orientation of the
instrument. The Probe Check can also give valuable information about data quality if you are close to
a boundary.
5.3.4 Incorrect speed of sound
The speed of sound in water influences the calculation of the velocity data. The time lag between the
transmitted and received pulse determines how far the pulse travelled before it was reflected.
The instruments compute the speed of sound based on the measured temperature (accuracy of 0.1°
C). A nominal salinity is assumed, an assumption that works relatively well because the sound
speed is more sensitive to temperature variation than it is to salinity variation.
Sound speed errors are typically small, but if you must correct velocity data for errors, use the
following equation:
Here, V is the velocity and C is the speed of sound.
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