Tao Wen

Paired Characterization and Preliminary Correction of Low-Cost Soil Moisture Sensors for Wireless Sensor Network Application

In order to fulfill the need of minimizing sensor cost and characterizing sensor agricultural application for the promising wireless sensor network technology, this paper evaluates a pair of SMC sensors (EC-5 and 5TE) under some laboratory experiments which is based on a standardized sensor characterization methodology using liquid medium with a known standard water content. The results showed that the electronics of the EC-5 and the 5TE are sensitive to temperature, electric conductivity and pH variations and it is concluded that both the 5TE sensor and the EC-5 sensor are suitable for wireless network applications. Moreover, the results of this paper also suggested that the effects of temperature, electric conductivity and pH on the sensor measurement ability have to be compensated using the appropriate correction functions. Future work will focus on the field application of these sensors and their correction effects in more detail to derive more general correction functions.

Data transmission performance for 2.4GHz in-field wireless sensor network

Wireless sensor network (WSN) technology is a promising solution for large-scale, real-time, and continuous soil property data acquisition. However, the applications are still very limited due to a lack of understanding of the WSN in-field data transmission performance. In this study, commercial 2.4GHz wireless sensor modules were used to set up a test platform to evaluate data transmission performance. Indexed packets transmitted from a module were received by another equal module to calculate packet delivery rate (PDR). Experiments were conducted in a wheat field of an experimental farm of Oklahoma State University. Canopy height, transmitter height, receiver height and transmitter-toreceiver distance (T-R distance) were considered as impact factors on data transmission. Correlation analysis was used to evaluate the relationship between path-loss and PDR. The results indicated that, with the increase of the plant height, path-loss and PDR became more correlated with each other. A distance of 70m was defined as a stable communication distance for the 2.4GHz in-field WSN applications.