SYSTEM FOR AUTOMATING AND MULTIPLEXING SOIL-MOISTURE MEASUREMENT BY TIME-DOMAIN REFLECTOMETRY

It is often necessary to measure soil water content at multiple points in space and time. Our goal was to develop an automated and multiplexed measurement system using time-domain reflectometry (TDR). Two systems are described; the first (A) uses an analog TDR unit, in which voltage signals sent from the TDR to a datalogger convey the shape of the waveform. The second (D) uses a digital TDR that communicates a digital representation of the oscilloscope wave to a personal computer. The systems described should be useful for field research on many subjects, including studies of transport and biological processes in soil, and validation of root water-uptake models. -from Authors