For full details including BOM, OpenSCAD, instructions, and results go here: http://www.appropedia.org/Open-source_mobile_water_quality_testing_platform For technical details read the paper here: Bas Wijnen, G. C. Anzalone and Joshua M. Pearce, Open-source mobile water quality testing platform. Journal of Water, Sanitation and Hygiene for Development, 4(3) pp. 532–537 (2014). doi:10.2166/washdev.2014.137 open access: https://www.academia.edu/8319858/Open-source_mobile_water_quality_testing_platform