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Soil Moisture Sensor SMT 100

Combined FDR sensor for soil moisture and temperature

The FDR measurement (= Frequency Domain Reflectometry) is, similar to the TDR measurement (=Time Domain Reflectometry), a volumetric determination of the absolute water content in soil or substrates. The measuring principle is based on the change or the transit time of electromagnetic waves which are emitted and received again by the sensor.

Due to the fast response of the sensors and universal applicability for all types of soil and substrate FDR sensors are most helpful for automation of irrigation control. Water content data (expressed in Vol %) allow immediate statement about the Irrigation water requirements. In contrast to the usual ime control technologies, due to the prompt response of the sensors even moisture- dependent shutdown of the Irrigation is possible.

Another advantage is that chemical properties of the soil (pH, salinity) have no or only a negligible influence on the measuring results. The sensors are frostproof, maintenance free and have a very long service life. Please note that measurement values should be adapted to the soil type or the substrate composition during evaluation. In addition, the capacitive measurement method requires careful installation of the sensors, providing good soil contact; air gaps and hollow spaces on the sensor affect its measuring accuracy.

The SMT 100 Soil Moisture Sensor is applicable for:

  • Individual and mobile measurement with the handheld reader MST 3000+
  • Stationary use combined with data logger and / or complete weather station in the field (T-Warner ECO Soil Moisture)
  • Stationary use for efficient automation of irrigation control (Irrigation Computer)
  • With digital output (see technical data).

Areas of application: growing media, such as peat substrates, coconut fiber, bark substrates, etc. Mineral Substrates such as rock wool). Directly in containers, pots and grow bags. Ideal for indoor greenery. Outdoors in Mineral soils, for example for irrigation control of agricultural areas, viticulture and hop cultivation. Open ground vegetables, asparagus, strawberries and berry fruits. Experimental procedures, such as drought stress experiments.

Technical data:

  • Meas. range: 0 – 95%, -20 to +80°C
  • Accuracy: ±2%, ± 0.8°C
  • Accuracy after spec.calibration: ±1%, ± 0.8°C
  • Resolution: 0.1%, 0.1°C
  • Output: digital RS 485 with T-Bus protocol
  • Cable length: 5 m (on request up to 500 m)
  • Power: 4 – 24 VDC
  • Dimensions: 182 х 30 х 12 mm
  • Application: humidity and temperature measurement directly in the soil or substarte

Item-no.: 40820d – digital sensor SMT 100