We designed this open source pH, Dissolved Oxygen and Conductivity and Temperature Meter for teaching STEM students. We found that most open source equipment focused on robotics and electrical engineering. This device is meant for cross discipline teaching of chemistry, biology, and environmental sciences with computer science. The unit uses I2C communication between an Arduino Compatible Board and the main board. The main board takes care of the display, buttons, temperature measurement, electrochemical probe and data logging. By programming and designing the main board to manage the complex operations it frees up what is possible with the open source board. It also makes the device less "brickable". The open source board can control pins based on readings and display text, shapes and colors on the LCD screen. It can also be used to create graphs and active calculations on the LCD screen.