Extending the Limits of a Capacitive Soil-Water-Content Measurement

The capacitive component of soil impedance is a good measure for the water content. For long time people use rod-shaped pairs of electrodes to measure electrically the water content in natural- and artificial soil. Especially in high-conductive mediums, with conductivity as high as 15 mS/cm, this technique is not able to acquire the capacitive component of the impedance reliably. Because of the necessary usage of high measurement frequencies, physical effects, such as skin effect limit the applicability of long rod-shaped electrode pairs. Having analyzed this problem a new electrodes structure has been built and tested to reduce this unwanted physical effect thus enabling reliably water-content measurements.