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A manually controlled TDR soil moisture meter operating with 300 ps rise-time needle pulse

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The principle of operation of a simple, manually controlled Time Domain Reflectometer (TDR meter) for soil moisture measurements, which operates with a needle pulse of 300 ps rise-time, is described. A block diagram and constructions are also given. Construction of a switchless multiple sensor probe, having an inherent delay reference, is presented. Results of measurements of the soil dielectric constant as related to water content, for soils having different bulk densities, textures and humus content show a high correlation. The results agree closely with other investigators measurements with different, more expensive, TDR instruments. The general principle of microprocessor-controlled TDR operated soil moisture meter is considered.

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Malicki, M.A., Skierucha, W.M. A manually controlled TDR soil moisture meter operating with 300 ps rise-time needle pulse. Irrig Sci 10, 153–163 (1989).

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