The objective of this paper was to implement an electromagnetic shielding, grounding and voltage surge protection in equipments for automatic soil water monitoring. The experiment was carried out in Piracicaba, São Paulo State, Brazil, using a Tektronix Cable Tester (Model 1502 B) that operates by time domain reflectometry (TDR) and a datalogger (CR10X, Campbell Scientific Inc., CSI) to control and analyze the waveforms produced by the cable tester. The water content was indirectly obtained by measuring the dielectric constant through probes inserted in the soil. For electromagnetic shielding the energy and signal cables were inserted in galvanized pipes, linked together by means of copper wire fixed in the pipes by bimetallic conectors. For the grounding, the copper wire was linked to copperweld stems, making a good contact bettween system and soil. To complete the electro-electronic protection, the powering of the TDR and datalogger was carried out by independent circuit with a proper disruptor, surge protection and no-break unity. The proposed system layout, which made use of preexisting materials as much as possible, presented an effective protection.
soil moisture; electronic protection; magnetic protection
