![](https://cdn.hackaday.io/images/8619531666293902846.jpg)
We just finished up a field season deploying OpenCTDs from commercial whale watching boats in New England, giving me a chance to discover all the new and novel ways for these devices to fail. After a summer of CTD casts, this unit finally gave up the ghost and the pressure sensor stopped logging. So I decided to cut it in half and get a look at things on the inside.
First note: this is one of our twice salvaged units from the 2020 field season, where we tested E-40HP (white) as the potting compound and discovered that it really sucked for this application, so there's a whole second layer of E-90FL (gray) in there, too. That was a rush fix and you can see how failed to fill some voids.
We go overkill on epoxy though, so as gnarly as this looks, it didn't leak.
![](https://cdn.hackaday.io/images/4583341666294139887.jpg)
You can see that the infill on the 3d printed baseplate did fill with seawater, and there's tons of salt crystals in there. This isn't a structural component, but it seems sub-optimal, so we'll be printing this part with 100% infill from now on.
![](https://cdn.hackaday.io/images/1444801666294220719.jpg)
And you can see the other other layer of clear 5-minute epoxy that we use to waterproof the pressure sensor components. it looks like wit didn't completely fill the voids, which is a problem that I believe we've fixed with a redesign of the baseplate that changed how the pressure sensor sits and how the epoxy flows around it.
And yes, we're doing something about that tangle of wires.
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