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SMT100 Soil Moisture and Soil Temperature Probe

Robust sensor for soil moisture and soil temperature

The SMT100 soil moisture probe uses Time Domain Transmission (TDT) technology. The SMT100 determines the volumetric water content and the soil temperature. It has a broad measurement range, it is maintenance free and frost resistant. With a robust design & manufacture and low power use, it is typically used for long-term observations (8+ years continuous use) and is well suited to IoT (Internet of Things) applications.

The SMT100 combines the advantages of the low-cost capacitance soil moisture sensor system with the accuracy of a TDR (time domain reflectometry) system. Like a TDR, it measures the travel time of a signal to determine the relative permittivity εr of the soil, and like a capacitance sensor, it converts εr into an easy to measure frequency. The SMT100 utilises a ring oscillator to transform the signal’s travel time into a frequency.