SonTek/YSI Argonaut-XR Technical Manual - HydroScientific West

SonTek/YSI
6.3. Argonaut Mounting and Installation
6.3.1. Argonaut MD
There are three common ways to mount the SonTek Argonaut MD: clamped to the side of a
mooring line, clamped to the side of a load bar, or mounted in an in-line load cage. The following
considerations should help ensure a successful deployment.
• Clamp the Argonaut securely; avoid pieces that may vibrate loose.
• Avoid flow interference due to beam alignment.
• Avoid excess magnetic material near the instrument; perform a compass calibration before
each deployment.
Secure mounting
The Argonaut MD can be supported either by circular clamps at two or more locations along the
pressure housing, or by a combination of one or more circular clamps and a supporting plate
below the lower end cap. The use of a supporting plate has the advantage of added security in the
event a circular clamp becomes loose. (Note: Any supporting plate must have a hole in the
center for the dummy plug from the power and communication connector.)
For deep-water deployments, be aware that the Argonaut MD pressure case may contract under
pressure. This can cause circular clamps that are secure at the surface to become loose. Be certain
to account for this in planning deep-water deployments.
When using in-line mooring frames, be certain that no portion of the frame is located directly in
the path of the acoustic transducers. The Argonaut MD transducers are designed to produce very
narrow beams (half power beam width is less than 2°). If all portions of the frame are at least 10°
outside the beam center, there is no potential for interference.
Magnetic material
The Argonaut MD uses a magnetic compass to report velocity data in Earth coordinates. Ferrous
metal in the mounting bracket or the mooring line near the instrument can affect the accuracy of
compass measurements and hence the accuracy of velocity data. All mounting fixtures should be
designed from non-ferrous metals, and other ferrous metals near the acoustic sensor head (less
than 1 m away) should be minimized.
A compass calibration should be performed before any deployment to account for any ambient
magnetic fields. If the Argonaut MD is installed on a mooring line made of ferrous metals, the
calibration can be performed using a short section (2 m long) of the mooring line mounted in the
same location as during deployment. This will simulate the effect of the mooring cable on
compass operation. When possible, perform the calibration away from large structures containing
ferrous materials (e.g., ships, buildings, areas with reinforced concrete). See §4.4 and the
Argonaut Software Manual for details on compass calibration.
Flow interference
Each Argonaut MD beam is slanted 45° off the axis of the pressure housing. The standard
Argonaut MD measures velocity in a cell ranging from 0.5 m to 2.0 m vertically from the sensor.
Since the beams are mounted at 45°, the cell starts with a radius of 0.5 m and has a maximum
radius of 2 m. The deep water Argonaut MD measures velocity in a cell ranging from 0.5 to
3.5 m vertically from the sensor (horizontal extent starts with a radius of 0.5 m, ends with a
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Argonaut Operation Manual Firmware Version 7.9 (May 1, 2001)