OpenCTD first soak test

Two weeks ago, we launched Oceanography for Everyone–The OpenCTD, a crowdfunding project to develop a low-cost, open-source CTD. After a few days hunting around for the best sealants, I put the prototype (name pending, suggestions welcome) through its first soak test.


OpenCTD first soak test. Please ignore how dirty my tub is.

The results were… mixed. I left the CTD soaking for 12 hours (with hardware removed) to see if there was any water incursion. Unfortunately, it seems like there is a small leak around the cap pipe cap. Total water incursion after 12 hours was less than 1 ml, but for us, that isn’t acceptable. Fortunately, we have a couple solutions in the works. For the prototype, we’re planning on adding teflon plumbers tape and additional sealant to help fill the voids. Longterm, we’re looking into a different cap assembly that would allow us to incorporate an O-ring into the assembly.

Developing a low-cost, open-source CTD costs time and money. You can helps us achieve our goal of making oceanography accessible to everyone by funding our Rockethub project–The OpenCTD.


  1. David Shiffman · June 10, 2013

    This is the same tub you occasionally drain the blood from 100 pound pigs in? I’m impressed by how NOT dirty it is.

  2. Don W · June 10, 2013

    you might try to make the end closure with 1/2 of a pipe union and a flat 1/4″ thick disk of plastic. that way, it’s o-ring sealed and the increase in depth/pressure acts to increase the sealing pressure.
    i’ve successfully used the construction with a piece of clear polycarbonate to make an inexpensive u/w video housing for a small helmet cam.

  3. Dave B · June 10, 2013

    There’s a discussion on DIY dive lights here that might have some interesting sealing details.

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