2. Other details
2.1 Power supply
The HT-S is powered by the Spotter via the Smart Mooring cables. In turn, Spotter possesses an internal battery, charged by the 5 x 2W solar panels.
Always use the provided charger, to charge the Spotter.
2.2 Memory
The HT uses a SD card with a capacity of 256 GB. This is enough for deployments of up to 2 months, assuming a power cycle of 14 minutes every half an hour, recording 16-bit WAV files at 48 ksps.
The SD card can be upgraded to 512GB and 1TB (and even 2TB, as long as its SDXC type) thus increasing the length of the deployment. To format the microSD card, it is recommended to use a tool such as the official tool from https://www.sdcard.org/downloads/formatter/ , which is careful to align the FAT filesystem clusters to the physical erase cycle size of the card. The card should be larger than 64GB, so that the tool picks up exFAT and not FAT32, which would be prohibitively slow. After installing you should open the app select the card you want to format, leave the default Quick format option on just press Format.
2.3 Retrieval of data files & Opening the Enclosure
The HT-S stores raw lossless acoustic data in WAV format in its SD card. This data only can be accessed upon retrieval of the HT from the water and by opening the enclosure. If you intend to do it, and are not sure how to do it, please contact the Hydrotwin team.
When opening the unit after retrieval, ensure always that the hydrophone is dry, to prevent water ingress, which could damage the electronics inside.
When opening the unit, the hydrophone lid can make some resistance. Pull it with care, to prevent a sudden release that could pull the cabling inside, and consequent damage.
Also, when opening the unit, do not use any metal, sharp or pointy tools that could damage the case and its watertightness. If necessary, use a plastic tool to help gently lifting the lid.
The steps to open the enclosure and access the SD card, where the raw acoustic files are stored, are as follows:
Pull and remove the locking cord from the cap/lid where the hydrophone transducer is located (with the small cage around it).
Remove the cap by pulling it. Gently oscillating it can help release it. Make sure not to apply to much force, which could suddenly release it and damage the cabling inside.
Do not remove the cable that's attached to it, it should provide enough leeway for the following steps.
On the bottom of the lid there is a circular green circuit board. Locate the SD card. To remove it, push it inside. It will click, and release. You may pull it out now.
At this stage, either open the SD card in your laptop, and then delete its contents. Or, if you prefer, slide in a new empty one. If so, please ensure it is correctly formatted (Section 2.2 - Memory).
The raw audio files are stored with the respective ISO timestamp it started to be recorded in UTC: <YYYYMMDDTHHMMSS>.wav.
While the acoustic signal is processed in 1-minute packages, the files are stored according to the power cycle length (default is 14 minutes).
After the data retrieval is complete:
Insert the (new) SD card. Push it inside, a click sound should indicate it is locked in place.
Carefully clean the O'Rings in the cap and apply some Molykote (or similar). A very small quantity is enough, so a single pack is enough for multiple applications.
Apply a small quantity in your finger, and spread it around the O-rings, ensuring they are clean.
Put the cap back on. Slight oscillations may help this step. Note that in the cap there is a small protrusion. It should align and fit into the dent in the enclosure, where the locking chord was present. Ensure that the cap and the enclosure are tightly fit.
Slid back in the locking cord.
Ensure that before closing the lid, the O-rings are clean from any debris, dust or hairs. Even small quantities can compromise the watertightness of the system.
The protrusion in the cap should align and fit into the dent in the enclosure. Failing to do so implies that the system is not properly closed and compromise watertightness.
The following video provides you a visual guide, to understand these steps:
Do not open the cap in the other hand of the system, since it might damage the equipment.
2.4 Clock details
HT-S clock is synchronized with the GPS clock of Spotter every time a new power cycle starts. The reference time used is always UTC, independently of where the system was deployed.
2.5 Depth rating
As supplied, the HT is rated for deployments up to 65 m depth. This does not prevent the selection of deeper deployment sites, up to 200 m depth, as long as HT does not exceed the rated 65 m depth in the water column.
2.6 Software and firmware updates
New software releases will be made available with Hydrotwin Intelligence subscription. These updates can be done remotely by the Hydrotwin team, as long as the unit is connected to the internet. That is, the unit must be recovered to shore.
In order to prepare this, turn ON Spotter, and place it in a location with a clear sky-view. Ensure that all 3 lights turn green, ensuring GPS signal is fixed.
Prepare also a network with the following characteristics:
- SSID / Network Name: borealis
- Password: borealis
Please ensure that the network provides Internet access, you may even use your phone to create this network. Note that after first turning ON the Spotter, the hydrophone may only turn on and connect to the network after 30 minutes.
Eventually, if the hydrophone is able to successfully connect to your network, the Hydrotwin team should be able to remotely update the unit.