Soil moisture, or the volumetric percentage of water in soil, has become an important consideration in the design of environmental re mediation processes and agricultural planning, and it is one of the most fundamental factors influencing soil strength. VERTEK’s Soil Moisture/Resistivity (SMR) Module provides real-time, in-situ logs of soil moisture and resistivity without sampling.
Soil Moisture Measurement:
The SMR module takes advantage of a relationship between the soil dielectric constant and moisture, widely known as Topp’s Equation. This relationship is not strongly influenced by soil type and resistivity if the dielectric measurement is made above a critical frequency of approximately 30 MHz. The inner two electrode rings of VERTEK's SMR module determine the soil's moisture content by measuring the frequency shift of a high frequency excitation signal as it passes through the soil near the surface of the module.
The outer two rings of our four-electrode ring design are used to measure resistivity. An AC voltage signal of constant amplitude is applied across the rings. A voltage measurement, which is proportional to the current through the soil, is made across a sampling resistor. The VERTEK Data Acquisition System and proprietary software provide a soil resistivity readout in ohm-meters.
Geotechnical and Environmental Applications:
Soil Moisture Resistivity - SMRs - are available in a variety of diameters and configurations for use in a number of applications, including geotechnical, environmental, and agricultural. An SMR Module can be used in conjunction with a CPT cone penetrometer to provide soil moisture/resistivity data simultaneously with tip, sleeve, and pore pressure data.
Long Term Monitoring:
An array of Soil Moisture Resistivity probes can be permanently emplaced with a field-based data logging or acquisition system. Several communications options (cabled and wireless) are available for long-term monitoring to optimize irrigation of high value crops and to detect leakage of contaminants into or from landfill areas and hazardous waste sites.
ISO 9001-2008 Certified The SMR module does not require delicate tuning or complicated maintenance and can be field calibrated using water and air. Continuous moisture logs can be generated at the standard CPT advance rate of 2cm (one measurement) per second, so moisture surveys can be completed with the geotechnical site characterization at no additional operating cost.
The SMR module fits behind a 15 cm2 cone and works with Vertek’s Data-Pack 2010SV or Mini Datapack. No additional software is required.