SonTek/YSI
12
ADVField Operation Manual (September 1, 2001)
ADV enters a low power standby mode when not collecting data). Using the above parameters,
the ADV generates between 230 and 630 KB of data per day.
Users are often interested in different aspects of the velocity field that require different sampling
schemes. Examples might include mean currents (requiring slow sampling rate), waves (requir-
ing a moderate sampling rate; 2-5 Hz), and turbulence (requiring a rapid sampling rate; ≈25 Hz).
The autonomous ADV has been designed to allow up to three different burst types to be collected
in a single deployment. Each burst type has independent values for burst interval, sampling rate,
and samples per burst. To avoid conflicts, these parameters are subject to the following rules.
1. The burst intervals for types 2 and 3 must be integer multiples of the burst interval for type 1.
2. The sum of the three sampling times must be at least 15 seconds less than the burst interval for
type 1 (to allow an overhead of 5 seconds for each burst).
The last type of sampling in Figure 7 shows multiple-burst sampling; lines of different heights
represent different burst types. Multiple burst sampling is best described with an example.
Suppose you are interested in mean currents, waves, and turbulence for a particular deployment.
For mean currents, you might sample at 0.2 Hz (every 5 seconds) for a period of 2 minutes, and
repeat the sampling every 20 minutes. For waves, you might sample at 4 Hz for a period of 5
minutes, and repeat the sampling every hour. For turbulence, you might sample at 25 Hz for a pe-
riod of 5 minutes, and repeat the sampling every two hours. To do this, you could set the parame-
ters shown in Table 2.
Note
: Changing the sampling rate does not effect power consumption. As described earlier, the
ADV pings as rapidly as it can, given a certain velocity range and configuration settings,
regardless of the sampling rate. However, changing the velocity range does
change the
power consumption.
To calculate the total duty cycle, add the duty cycle from each burst (for this example, it is about
23%). When calculating memory requirements, the burst interval as well as the amount of data
must to be taken into account. The example shown here would generate 0.8 to 2.3 MB of data per
day, depending on what parameters are recorded (see §3.7). All data is stored in one file, and the
data conversion software accesses each burst type independently to simplify its presentation and
to separate the burst types for analysis (see ADVField Software Manual for details). Multiple-
burst sampling supports a wide variety of sampling strategies in a reliable and easy to use format.
Burst Type 1:
Mean Currents
Burst Type 2:
Waves
Burst Type 3:
Turbulence
Sampling Rate (Hz) 0.2 2.0 25.0
Samples per Burst 24 600 7500
Burst Interval (s) 1200 3600 7200
Sample Time (s) 120 300 300
Burst Duty Cycle (%) 10.4% 8.5% 4.3%
Kbytes per Burst 0.2 - 0.5 4.8 - 13.2 60 - 160
Table 2. Example Parameters for Multiple-Burst Sampling Strategy
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