An Alternative Heat Pulse Sensor Design.

Timely and accurate measurements of soil water content are important for characterizing and managing hydrological systems. Knowledge of temporal and spatial water content distributions is essential for maximizing crop production in agricultural systems and for understanding biodiversity of natural ecosystems. In addition to being an important state variable, water content is also interrelated with fluxes of heat and water, which are highly variable processes in the vadose zone. Despite the vast importance of soil water content, measuring it is challenging and is mostly limited by capabilities and cost of sensors.

Heat pulse sensors are advantageous for measuring soil water content and thermal properties. Measurements with these sensors are soil independent and data acquisition requirements are relatively simple. However, there is need for durable heat pulse sensors that can be used in harsh field conditions. In order to address this issue, we propose a more rigid design. Instead of applying the line-source model to interpret measurement data, we account for the geometry of the sensor with a different heat transfer model. We present preliminary results from soil measurements.