SonTek/YSI Argonaut-XR Technical Manual - HydroScientific West

SonTek/YSI
1.2. Definitions and Terminology
This section defines terms commonly used when working with the Argonaut.
• Direct command interface - direct serial communication with the Argonaut to control system
operation and retrieve data.
• BREAK - a serial communication signal that causes a hardware reset in the electronics and
returns the Argonaut to command mode.
• Ping - a single estimate of the water velocity. A ping consists of each transducer sending an
acoustic pulse, listening to the response, calculating the along beam velocity, and combining
data from all beams to compute the 3D velocity.
• Sample - refers to the collection of a number of pings to produce a mean estimate of water
velocity. The mean sample includes velocity, standard deviation, and signal strength data, as
well as data from other sensors.
• Temperature - water temperature, in °C, is used for sound speed calculations. A default value
is entered by the user, and another value is measured using an internal temperature sensor.
• Salinity - water salinity, in ppt; a user-supplied value is used for sound speed calculations.
• Sound speed - speed of sound in water, in m/s. This is used to convert the Doppler shift to
velocity. Sound speed can be calculated either from user-specified temperature and salinity,
or from measured temperature and user-input salinity (see TempMode in §3.8 for details). See
Argonaut Principles of Operation regarding the effect of sound speed on velocity data.
• Measurement volume / sampling volume – the volume of water in which the Argonaut
measures velocity. This volume is at a fixed location for the Argonaut MD, and is userprogrammable
for the Argonaut XR and SL.
• Cell begin – the location of the start of the measurement volume for the XR and SL. This is
set by the user and is measured as distance along the axis of the instrument housing.
• Cell end – the location of the end of the measurement volume for the XR and SL. This is set
by the user and is measured as distance along the axis of the instrument housing.
• Dynamic boundary adjustment – the automatic modification of the XR sampling volume
based on data from the pressure sensor. This can be used to adapt operation to changing conditions
in environments where surface elevation varies (e.g., tide or river stage variations).
• Pinging rate - the number of pings per second, in Hz. The Argonaut is programmed to ping
once per second.
• Sample time - the Argonaut records date and time from its internal clock with each sample.
The recorded time represents the start of the averaging interval.
• Averaging interval - the period, in seconds, over which the Argonaut averages data before
computing mean velocity.
• Sample interval - the time between sequential samples, in seconds. This is defined as the time
from the start of one sample to the start of the next sample, and must be greater than or equal
to the averaging interval or the averaging interval will take precedence.
• Burst sampling - this sampling method allows you to record a number of samples in rapid
succession, and then place the Argonaut in a low-power state for an extended period. This
obtains information about both the short- and long-term variation of water velocity without
the power and memory required for continuous sampling.
2
Argonaut Operation Manual Firmware Version 7.9 (May 1, 2001)