The COAST Lab's Open Water Level Meter Is a Smart, Low-Cost Sensor Built Around Off-the-Shelf Parts
Low-cost sensor, driven by an Adafruit Feather M0 Adalogger, can go toe-to-toe with expensive commercial alternatives.
A team from the Coastal Ocean Applied Science & Technology (COAST) Lab at the University of North Carolina Wilmington (UNCW), working with the Birch Aquarium at Scripps and the San Diego Unified School District, has designed a low-cost yet high-accuracy water level sensor system based on an Adafruit Feather M0 Adalogger — and has released the design for all to use.
"Through a collaboration between our research team, the Birch Aquarium at Scripps, and San Diego Unified School District, we undertook the design of a low-cost and open water level sensor," Phil Bresnahan, assistant professor at UNCW and first author on the paper detailing the sensor, writes in an introduction to the project brought to our attention by Adafruit. "The initial goal was to build a simple and inexpensive device that could be assembled by high school students prior to field trips to the site of the future Seaport Learning Center in downtown San Diego, then deployed for real-time data collection during those field trips."
The sensor's designs is based entirely on affordable off-the-shelf parts, beginning with an Adafruit Feather M0 Adalogger microcontroller board logging to a local microSD card. Real-time clock (RTC) and OLED display FeatherWing boards are added, along with a Maxbotix LV-EZ4 ultrasonic rangefinder to take measurements between the sensor and the surface of the water — plus a lithium battery to keep everything ticking over.
"The sensor ended up working so well (~1cm [around 0.4"] root mean squared error vs. a much more expensive commercial unit)," Bresnahan notes of the sensor's capabilities, "that we are now beginning deployments in coastal and estuarine settings where communities need additional real-time water level monitoring solutions."
"For just over $100, only a small amount of soldering, and installation of ready-to-use code, other students and educators, communities in need of water level monitoring, and potentially researchers can construct a simple but reliable device," the team concludes of its creation.
"Building, deploying, and analyzing data from the sensor can aid in students’ understanding of water level measurements and in the practice of monitoring sea level changes," the researchers continue. "Ultimately, we believe that this DIY water level sensor can improve ocean and climate literacy while providing a hands-on project that teaches real-world engineering and science skills."
The team's work has been published in the journal Oceanography under open-access terms, while the latest version of the design — including an updated bill of materials which offers a Bluefruit Feather nRF52832 or Particle Boron as an alternative to the Adalogger, the latter offering cellular connectivity — has been published with full source code to GitHub under the permissive MIT license.