YSI ADV6600 - Manual (Page 45)

ADV6600
Y S I
Environmental
Page 35
Section 4. Calibration and Diagnostics
All of the sonde sensors, with the exception of temperature, require calibration before the ADV6600
can be used. In addition, periodic calibration and/or diagnostics are necessary to assure accurate
performance.
4-1. Beam Check Basics
It is critical to assure proper performance of the ADV sensor prior to any field or laboratory study
and the “Beam Check” capability of the ADV6600 allows the user to easily evaluate the basic
performance of the Doppler sensor. Using this program on a regular basis, or, at a minimum, prior
to each deployment, is the best way to ensure consistently good ADV data.
Beam Check operates by sending a pulse of sound into the water, and then plotting the signal
strength of the return signal versus range (or time) for each of the instrument’s receivers. Features
in the returned signal strength profile (or amplitude) are then used to verify different aspects of
system performance. For most applications, the user can simply look at the plot to confirm proper
ADV functionality as evidenced by three factors:(a) all three receiver channel outputs are aligned
(plotting on top of one another – not offset horizontally), (b) the amplitude of each receiver at the
sampling volume is more then 10 counts above the baseline, and (c) the system has been placed
such that the sampling volume of the ADV is sufficiently spaced.
4-2. Running the ADV Beam Check
Initially, a Beam Check should be run in the laboratory using the procedure outlined below to
confirm that the ADV sensor is functioning properly under ideal conditions. It is particularly
important, however, to also perform the Beam Check at the site where the data will be collected
(i.e., the system should be deployed as it will be under study condition). In addition, it is strongly
recommended that a Beam Check be performed and recorded before and after each deployment
(before cleaning or changing the location of the ADV6600). The Beam Check procedure is quick,
and the results can be either printed or stored to a computer file for use in QC/QA programs. It is
particularly important to note that the ability of YSI Technical Support personnel to aid in data
analysis and troubleshooting will be significantly compromised if a beam check file from the site is
not available.
The Beam Check test at the site will answer the following questions::
• Are there sufficient scatterers in the water to collect data.?
• Is the system operating correctly?
• Is the distance to the boundary (if present) sufficient?