STELZNER® agricultural measurement systems

Volume sensors

Volume sensors measure the water content of the soil or substrate in volume fractions; this is displayed as a percentage based on m³ of water per m³ of soil or substrate. It is a measure of the soil moisture and does not give information on the availability of water (suction tension of the soil). It is a direct capacitive measurement. The volumetric sensor forms a capacitor with the soil, the capacitance of which changes with the change in the dielectric property of the soil due to the changing humidity. It should be noted that the dielectric property of the soil is also determined by its structure.
The volume sensors need clear contact. Thus, hollow cavities at the sensor must be avoided at all costs. The salinity of the soil also influences the measurement. For accurate measurements, the sensor should be calibrated according to the respective soil type.
Volume sensors are maintenance-free, very stable and suitable for installation underground.

Volume sensor SMT50
Measurement of soil moisture according to the FDR principle (Frequeny Domain Reflectory) for simple measurements in the range of 0 to 50 vol. %. Measuring surface: approx. 9 x 2 cm

Volume sensor SMT100
Measurement of soil moisture according to the TDT principle (Time Domain Transmissionmetry) for accurate measurements in the range of 0 to 100 vol. %. Measuring surface: approx. 11 x 3 cm; sensor has programmable settings.

Aquaflex
Measurement of soil moisture according to the TDT principle (Time Domain Transmissionmetry) for measurements in the range of 0 to 100 vol. %, as a mean value over the length. The measuring tape is approx. 2 cm wide and either 100 or 300 cm long. Well suited for row crops with drip irrigation or for lawn irrigation.