I just read an article in AEE – Advances in Engineering Education—A Journal of Engineering Education Applications, vol. 3 #2, 2012, SENSE IT: Teaching STEM principles to middle and high school students through the design, construction and deployment of water quality sensors:
This paper describes the structure and impact of an NSF-funded ITEST project designed to enrich science, technology, engineering, and mathematics (STEM) education using educational modules that teach students to construct, program, and test a series of sensors used to monitor water quality.
The four sensors that they used for the middle school and high school students (thermistor for temperature, LED and photoresistor for turbidity, pressure gauge for depth, and electrodes for conductivity) would be suitable for the freshman design seminar. I already use the thermistor lab as the first lab in the circuits course, and I do a more sophisticated version of the conductivity and pressure sensor labs (measuring impedance with polarizable and non-polarizable electrodes and using a pressure sensor that is just a strain gauge, so that they need to build the amplifier for it). Details of the curriculum and the sensors themselves can be found at http://senseit.org
The application to water quality measurements is reasonable, and for the freshman seminar it might be worth a field trip down to San Lorenzo River or Cowell beach to test out their designs.
We would use Arduinos or KL25Z boards, rather than Lego NXT bricks, and waterproofing their designs could be a part of the engineering. Using a drybox and a connector should not be too difficult. The robotics club has used IP68 Sealcon strain reliefs from www.productsforautomation.com for cables and Buccaneer mini IP68 connectors for disconnectable connections, both successfully. Some parts could be potted in epoxy, like the cameras for the underwater robot.
My main concern is that making the instruments be standalone might be too challenging, but just duplicating what the high school students do might not be challenging enough. I also don’t want to have to teach half the circuits course for the freshman design seminar, so I’d like to keep the necessary electronics to a minimum.