STELZNER® agricultural measurement systems

Measuring instruments for soil moisture and water monitoring, using sensors, tensiometers and data loggers

Volume sensors for HYDRO 2000

Determining the volumetric water content in the soil

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.


The HYDRO 2000 is an inexpensive measuring device for professional use. It determines the volumetric water content in soil. The SMT 50 sensor works according to the FDR (frequency domain reflectory) principle. It delivers precise results in the relevant measuring range between 0 and 50 % water content by volume, with only slight influences from salinity and soil type. The cable and housing for the sensor are waterproof.

In addition to measuring soil moisture, the HYDRO 2000 can also measure the temperature of the soil. Thanks to its compact and robust design, this measuring device is maintenance-free and suitable for continuous operations.

The HYDRO 2000 can be optionally deliverd with a cable connection for connecting further volume sensors  and to handle additional measuring tasks.

30008098 Volumensensor SMT 50 € 149,94
with plug for Hydro 2000, 2m cable
30008089 HYDRO 2000 € 232,05
Hydro 2000 with plug connection
30008100 Volumensensor SMT 100 € 228,48
with plug for Hydro 2000, 2m cable
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Measuring range
of SMT 50:
volumetric soil humidity: 0 to 50 vol. %
    Temperature: -20 to +85°C
Measuring accuracy
of SMT 50:
Volumetric soil humidity: ±2% in mineral soils
with average salinity ranging from 0 to 50% (VWC)
 Temperature: typically 0.8%
Cable length: 1.2 m
Resolution: ±0.1 vol.%
Display: Liquid crystal display
Power supply: One nine-volt battery,
    size 6LR61
Degree of protection: IP 40
Dimensions and weight: 125 x 78 x 45 mm, 190 g

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