Sunburst Sensors is a small company that won the Wendy Schmidt Ocean Health XPRIZE in 2015. We entered 2 separate instruments to win both the affordability and accuracy purses. Since then we have turned the 'affordability' design into a real world product that is used by many researchers - the iSAMI-pH (i for 'inexpensive') shown here: http://sunburstsensors.com/products/isami-ph.html