A Computer-Controlled 36-Channel Time Domain Reflectometry System for Monitoring Soil Water Contents

Research on the spatial and temporal dynamics of soil water has long been impeded by the lack of an automated technique for the measurement of soil water content. A computer controlled time domain reflectometry (TDR) system is described which gives the possibility of making a large number of measurements at different sites at predetermined time intervals. The developed system operates on 12 V dc and has the capability to monitor water contents at 36 sites. The algorithm used for the automatic analysis of the measurements is also presented. It is based on the calculation of the travel time of the TDR signal between the beginning and the end of a three-wire probe.