Ocean Instruments SoundTrap ST640, Руководство пользователя

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3.2 Calculation of deployment endurance
An excel spreadsheet is provided on the website to help with the calculation of deployment times
for differing deployment parameters. The spreadsheet provides deployment estimates, as well as
identifying one of three possible deployment constraints: battery capacity, memory capacity, or file
count. While the first two are obvious, the file count constraint requires explanation.
The file system used by SoundTrap currently has a minimum file size of 4 MB. When using periodic
recording, if the programmed ‘record for a period of’ period is very short, the resultant file may be
smaller than the minimum file size. This will result in inefficient usage of memory, and the
deployment may be artificially memory limited. For example, a SoundTrap ST600 has 256 GB of
memory; dividing this by the minimum file size of 4 MB gives a maximum of 64000 files.
This limitation becomes an issue when using low sample rates in combination with X3 compression.
By experimenting with the periodic recording parameters in the deployment spreadsheet it will
become clear how to best avoid this limitation.
Be aware that lithium batteries should not be left in a discharged state for periods of more than a
couple of weeks. Doing so can result in a battery acid leak that may damage your recorder. To avoid
this we recommend adding a safety factor to your endurance calculations in case the retrieval of the
recorder is delayed. We also recommend a maximum deployment endurance of 1 year. Beyond
this endurance calculation becomes increasingly inaccurate, thereby risking earlier than expected
battery exhaustion and possible leakage.
3.3 ST640 multi channel recording
The ST640 supports connection of up to four external hydrophones. These are connected via four
wetplugs at the base of the recorder. Each wetplug has a number adjacent to it relating it to the
channel selection in the deployment settings.
ST640 output files are multichannel wav files where the channel numbering is from lowest to highest
physical channel number. For example - recording on channels 2 and 4 only would result in a two
channel wav file with the 1
st
wav channel pertaining to the 2
nd
physical channel.
Recording endurance will be reduced by increased channel count due to both increased power
consumption and data rate. We recommend using our online endurance calculator to make these
calculations. Note that the calculator assumes use of HTI-96-MIN hydrophones which consume
approximately 3.6 mW. Use of other hydrophones may give different results.