The SMT-100 combines the advantages of the low-cost FDR sensor system with the accuracy of a TDR system. Like a TDR, it measures the travel time of a signal to determine the relative permittivity ε_r of the soil. And like a FDR, it converts ε_r into an easy to measure frequency. The SMT-100 utilizes a ring oscillator to transform the signal’s travel time into a frequency. The resulting frequency (>100 MHz) is high enough to operate well even in clayey soils.

Compact, functional and robust: the PCB board based design allows for an economic design, and the blade shape facilitates installation. The casing and cable are water sealed. The SMT-100 is connected to a logger or handheld for data management. Different communication protocols are available (RS485 or SDI-12), as well as analogue output. It is bus capable and thus, multiple sensors can be connected to one logger.

The SMT-100 determines the volumetric water content and the soil temperature. It has a broad measurement range, it is maintenance free and frost resistant. With a short response time and low disturbance by salinity it is designed for a long-term observation. Additionally, it is possible to retrieve the relative Permittivity.

The SMT-100 sensor is supplied as standard with a reader for mobile measurement of volumetric soil moisture and soil temperature in a transport case.

Advantages

• Frost resistant
• Reliable measurement
• Maintenance free
• Long lifetime
• Fast response
• Low influence of salinity and pH
• Cost efficient