Some quick feedback on what we’ve been up to with our Pioneer Program Dev Kit:
We’ve been hard at work getting to grips with the Bristlemouth ecosystem. Although the learning curve has been steep, we’ve achieved some excellent results and are excited about what the future holds.
We toyed with the idea of attaching a thermistor string to the mooring cable and managed to get a prototype going using the dev kit. After some trial and error, we ended up with what we thought would be a solid proof of concept sensor. Another request from the science folks was to provide high-resolution tidal data, so we integrated a pressure sensor as well.
Our test setup consisting of 10 temperature nodes and one pressure node:
Much effort went into stuffing as much information as we could into a small data structure and proving that we got the same results on the bench as what we got back from the API. Great job by @HendrikJvR to make this happen.
We did a test deployment in Cape Town harbour next to our polar vessel, the S.A. Agulhas II, which allowed us to use the onboard scientific echosounders to validate our results.
Do you guys keep the pressure sensor stable in the water column? Or is any movement of the sensor “within the noise” of the head of water you are measuring?
Just curious because we’ve been thinking about mounting strategies for longer term deployments and haven’t come up with a “great” solution for this yet…
Keeping the node as the very bottom of the system…the only thing that was below was the jaw-jaw swivel to relieve torsion and then the anchor.
Adding the in-line float about 0.5 to 1.0 meters above the node (which you said you tried)
shortening the overall scope of the mooring (from the Anchor to the surface float) to just a little over the depth (I think we ended up at 1.0x at low tide and 1.2x at high tide).
We put an IMU in the dev tube as well to measure the “layover” and did a little trig to find out what the total change in height would be and for us, for water level, it was within the acceptable error bar we were okay with. If we were doing single wave analysis or seiching or meteotsunamis or storm surge we’d for sure have to fix the pressure sensor to the bottom somehow.
One of my colleagues came up with a pretty clever mooring design that allowed for a fixed point bottom mount that they liked but it had trouble staying upright. Note that the final connection is not rotating but fixed.
At this stage our requirement doesn’t require mm precision, for the example above we were running 5 minute averages.
That fixed point mount is pretty neat. Not having a swivel on the bottom opens up a whole new set of opportunities for connection to bottom mounted infrastructure.
How long did you have that setup out in the wild? Can it handle a bit of weather? No issues with torsion stresses on the mooring line?
Notice the wider base and that it DOES include a swivel to relieve torsion built up in the mooring which I highly recommend. In some places it’s not necessary but where there is frequent switching of wind or currents like here at Ocean Beach in San Francisco CA it becomes necessary.
We’ve not tested any of these designs ourselves, I think this one is installed in Puerto Rico.
