Electronics That Can Handle The Pressure

Deep-sea exploration is considered as a relatively new area of research and the electronics involved has to be special in order to survive some of the deepest parts of the ocean. Pressure Tolerant Electronics is a new subject and has its own challenges as explained by [Nic Bingham] of the Schmidt Ocean Institute.

[Nic Bingham] was one of the speakers at the Supplyframe office for ‘The Hardware Developers Didactic Galactic’ held April 20th 2017. His talks was based on his experience with ambient-pressure electronics and autonomous solar-diesel power plants at the Antarctic plateau. Due to high pressures at large depths, the selection of components becomes critical. Low density components such as electrolytic capacitors have either air or fluids which are susceptible to compression under water and prone to damage. Since pressure tolerance is not part of most datasheet figures, component selection becomes difficult and subject to prior testing.

There are other challenges as well as [Nic Bingham] explains that revolve around the procurement of special parts as well as spare for older components. In his whitepaper, [Nic Bingham] chalks out everything from the development process to different testing methodologies and even component selection for such applications.

A video of his talk is worth a watch along with the nice writeup by [Chris Gammell] on his first hand experience of the lecture. For those who are looking for something on a budget, the underwater glider project is a good start.

11 thoughts on “Electronics That Can Handle The Pressure

  1. I would think that the best way to make tolerant electronics would be to turn your entire system into a big-ass ASIC. We really need to get on the ball with the DIY silicon machines.

    1. You assume correctly (you can have mineral oils with different electrical characteristics that you want to be familiar of course). I work for a company that develops marine technology, mostly sonar systems and AUV’s, we use a mineral oil in all our PBOF enclosures.

    2. You assume correctly. I work for a marine technology company, we develop sonar systems and AUVs. We use mineral oil in all our PBOF enclosures. You want to be sure your familiar with the electrical characteristics of the oil your using, as well as the potential for chemical interaction with anything the oil will be in contact with in your system.

    1. Water “shrinks” by two some odd percent at extreme depths, more if you continue pressurizing it. Depending on the vessel design and surface area / volume, this could lead to considerable forces that you would otherwise not encounter at atmospheric pressures. You also need to consider the water’s thermal expansion from depth to the surface as well. It’s quite cold at the bottom of the ocean, which also slightly modifies the calculations.

      Although it is a little unclear why they are trying to design things like capacitors without air or fluids? Are they intending them for use inside an open to the water type application? What would the advantage(s) of that be specifically?

      Also, there are at least two minor typos in the article.
      “Low density components such as electrolytic capacitors have either air or fluids which are susceptible to compression under water and [are] prone to damage.”

      “as well as spare[s] for older components”

      1. The main advantage of components that are ‘solid throughout’ instead of having internal gaps filled with either air of fluid is that they would be better able to handle pressure variations. It’s not an open-to-the-water application, but rather to install electronics in an ambient-pressure bladder (basically a mineral or silicone oil filled bladder) instead of a bulky and heavy pressure vessel. Wall thickness requirements (and thus weight) goes up surprisingly fast with enclosure size and pressure differential. The weight saved by skipping the pressure vessel means you also need less added buoyancy to compensate, so the size of the vehicle drops substantially.

        1. It’s the point of the talk but can one design off the shelf systems that are tolerant to such temperature and pressure extremes that work reliably given they are no longer isolated from the pressures? It’s obviously cheaper, easier, less bulky and so on but are a wide enough range of components available to make such a unit viable without needing to custom engineer entire segments of electronic components? I remain skeptical that an ambient pressure bladder represents a preferential method of designing such a system given those constraints. I suppose it depends on expected depths to a degree.

          It obviously also depends on what the unit is designed to do exactly but such a system feels significantly more challenging to build and fought with a considerable amount of potential issues, even if the potential savings appears to be fairly substantial (resource wise) as you scale the system up?

          Most electronic systems are generally compact in nature anyway and pressurized connectors are standard off the shelf components. Not saying this research has no merit, just curious as to how big of a benefit it actually provides for a high pressure, deep water environment compared to the status quo of a pressure vessel type enclosure.

          1. TFA answers all these questions and the answers are quite interesting. For these extreme pressures pressurized connectors aren’t standard and are hard to source and very easy to screw up in construction. He says that for depths to 6,000 meters there is a lot of standard off the shelf stuff made for the oil exploration industry, but past 6001 meters things get really specialized. He goes into some detail about the tradeoffs between trying to make COTS stuff work at pressure, putting it in vessels, and doing original pressure tolerant design.

  2. The means of pressure compensation he demonstrated for his enclosure (bringing seawater into a bladder within the enclosure) is an interesting way to approach such an issue. Pretty much all of the systems I’ve ever worked on would have an external pressure compensator, basically an flexible oil filled reservoir that is spring tensioned so that the oil system is always a few (5 to 10) PSI above ambient and then connected via hydraulic lines to all oil filled enclosures on the circuit. The advantage being that with your compensator outside of your electronics enclosure and the pressure held a few psi above ambient, if one of your enclosures seals leak, oil (usually a bio-degradable variety) will leak out of your system rather than water leaking in. When the system monitoring your compensator pressure alerts you that the pressure is dropping, you have time to recover your system before you flood an enclosure.

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