This Oceanographic Business Card Offers a Clever Way to Test OpenCTD Components

Offering a compact platform for testing sensors before they go off into the water, this is a truly smart contact card.

The OpenCTD project, which designs open source sensor devices for measuring conductivity, temperature, and depth (CTD) for oceanographic research purposes, has launched a new board — serving as a "calling card" as well as a bench test board for OpenCTD builders.

"OpenCTDs are designed to be calibrated, maintained, and deployed by ocean knowledge seekers around the world, regardless of experience level or institutional support," Andrew Thaler, PhD, explains. "Using an extensive build guide, OpenCTDs are assembled by the end user, building local capacity and providing a STEM experience for students."

"But we have a small problem," Thaler continues. "Because of how the OpenCTD is assembled, component testing doesn't happen until fairly late in the build, meaning that errors made early on compound, frustrating new and experienced users alike. To help alleviate this problem, we developed a bench test board."

The design takes the form of a PCB business card, which includes Thaler' contact information along with a link to build instructions. When fitted with components — an Adafruit Adalogger M0 Feather as the driving force, an Atlas EZO EC conductivity circuit, and an Analog Devices DS3231 real-time clock (RTC) — it also turns into a working OpenCTD, compatible with an external sensor package based on the TE Connectivity MS5803-14BA 14-bar pressure sensor, an Analog Devices DS18B20 temperature sensor, and a two-electrode conductivity probe.

In short: it's a fully-working OpenCTD, based on the project's move to being driven by an Adafruit Adalogger M0 Feather four years ago. Buildable in less time and at a lower cost than the standard OpenCTD board, it also serves a third purpose: with female headers, the core components can be inserted and removed at-will — meaning they can be tested before being installed in a full OpenCTD board, avoiding disappointment at the end of a two-day assembly workshop.

"By having a pre-made board which can test and verify each component of the CTD before they are incorporated into the larger project," Thaler explains, "students were better able to evaluate and troubleshoot their builds before committing sensors to epoxy or soldering components into place.

"Having the bench test board helped participants build confidence in their skills and made it easier to identify and correct potential issues during the build. It's more than just a fun business card. All future OpenCTD workshop will include one of these bench boards."

More details are available on; images of the board have been uploaded to the OpenCTD GitHub repository, but its design files were not publicly available at the time of writing.

Gareth Halfacree
Freelance journalist, technical author, hacker, tinkerer, erstwhile sysadmin. For hire:
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