Although there are some water tests than can be performed using probes, many require mixing reagents together and measuring the resulting color. The autotester replicates those steps. It has a carousel for up to 12 reagents. It can dispense drops and agitate both the reagents and the mixing cylinder to perform the tests. It is designed to make it easy to add different tests. It can remember the colors associated with the test results and score the resulting mixture.
It is raspberry pi powered and uses a pi camera with a fisheye lens. Stepper motors, electromagnets, and actuators are used to perform the tests. Computer vision software is used to control the device and evaluate the tests.
A full description of how to build one including 3D printed parts, build instructions, and software are available here.
A video of the earlier unit in use can be found here
Now can perform both direct read and titration type tests. More info here.