Advances in gas sensors and open-source hardware (e.g., Arduino) are enabling new options for low-cost and light-weight gas sampling devices that are also robust and easy to use and duplicate. In this project, we are developing a complete system for high-accuracy measurements of: temperature, relative humidity, luminosity, and CO2 concentrations. All measurements are logged with a GPS location and time-stamp. The system is assembled from only off-the-shelf products, with a total cost of less than $300. Validation of the system is conducted in a greenhouse.