YSI SonTek ADVField, Technical Documentation Manual

Page: 19 / 228

SonTek/YSI
ADVField/Hydra Operation Manual (September 1, 2001) 7
•
The acoustic sensor head contains three acoustic receivers and one acoustic transmitter. The
sensor head is mounted directly to the end of the signal-conditioning module.
•
The sampling volume is the volume of water ( ≈ 2 cm
3
) in which the ADV makes velocity
measurements. This volume is nominally located 18 cm from the acoustic transmitter.
•
The probe X-axis is defined by the direction of receiver #1, which is marked with a small in-
dentation on the sensor head. When looking from the sampling volume towards the acoustic
transmitter, the receivers are numbered 1, 2, and 3 moving clockwise from #1. The probe’s
X-axis is also stamped on the end cap next to the cable connector. (See §5.1 for coordinate
system details.)
•
The signal-conditioning module is a plastic housing with internal receiver electronics and op-
tional sensors. The acoustic sensor is permanently mounted to the lower end cap. The other
end has an underwater mateable connector for the high-frequency cable.
•
The optional pressure sensor is installed in the upper end cap (made of stainless steel) of the
conditioning module near the underwater connector to the high-frequency cable. Note that
since the pressure sensor is mounted away from the sampling volume, you may need to ac-
count for this distance when processing the combined pressure and velocity data.
•
The high-frequency cable to the processing module carries analog signals from the probe to
the digital processing electronics. This cable is highly sensitive to noise and should not be
modified, extended, or shortened without instruction from SonTek. The cable is connected to
the signal-conditioning module using an underwater mateable connector.
•
The ADVOcean probe with optional sensors has a total length of 39 cm (15.3 in), a maximum
housing diameter of 10 cm (4.0 in), and a maximum arm diameter of 20 cm (7.8 in) for the
circle about the ends of the three receiver arms.
•
The probe housing has mounting grooves to allow for easier and more secure mounting.