I used turbidostat interchangeably with a system to monitor and control turbididty, like with a thermostat.
Let start with a design concept, and more details on the circuit.
The Yun Shield runs a minimal Linux distro, and it can connect to the Internet, have USB ports and SD card slot, so the data can be logged to a USB stick or a SD card. The timestamp is retrieved from the Linux system, and the data file is retrieved through an FTP program like WinSCP or FileZilla or directly from USB, SD card reader.
Here is the code hosted on GitHub. Copy and paste the code to Arduino IDE, select the right port and the chip.
Here is the data logged in microSD card.