ELT-2 Volumetric water content sensor (VWC) Teros 12 The Teros 12 can retrofit the ELT-2 from Elsys and determines the volumetric water content (VWC) by measuring the dielectric constant of the medium using capacitance/frequency domain technology. The ELT Advanced Soil Moisture Sensor determines volumetric water content (VWC) by measuring the dielectric constant of the medium using capacitance/frequency domain technology. Its 70 MHz frequency minimizes salinity and structural effects, making this sensor accurate in almost any soil or soilless media. Factory calibrations for mineral soils, potting soil, rock wool and perlite are included. Note: This sensor requires a voltage of 4V and requires the ELT 5V Step-Up Module.