This system should monitor the pH, water temperature and water level of a small aquarium, and display each of the three sensor’s data in a PC terminal window. Although the system is relatively simple, it does require three independent subsystems to work together. This application note will break down each part of the system in the order they were created. This will allow a reader who intends to use this application note as a guide to build and test each part of the system independently. Once the reader is familiar with the process, they can expand the system or make modifications easily.