First Advisor

John M. Acken

Date of Award

Spring 6-14-2024

Document Type


Degree Name

Bachelor of Science (B.S.) in Computer Engineering and University Honors


Computer Engineering




Capstone Review, Water Activity, Wireless Network, Moisture Content, Equilibrium Relative Humidity, Carbon Sequestration


This paper highlights the progression of a two-term senior capstone project in the ECE department at Portland State University. Sponsored by Dr. David Burnett from PSU’s WEST Lab, the project aims to produce an affordable wireless monitoring system for water activity. The example scenario focuses on carbon sequestration where wood biomass is buried underground in enclosed capsules. For optimal sequestration, microorganisms capable of decaying the wood and releasing carbon back into the environment must be eliminated. Water activity, a key metric for measuring microbial activity, must be below 0.61 to prevent microbial survival. The system this project was designed for had to reliably monitor water activity data at a fraction of the cost of commercial water activity meters. Additional project goals included using OpenWSN, a wireless sensor communications network developed by UC Berkley, to transmit sensor data; graphically displaying water activity data; and exploring methods to measure water activity with relative humidity and moisture content sensors. This paper covers the necessary background to understand the project, our approach to solving the problem, and the results of our tests.