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 εr of the soil. And like a FDR, it converts εr 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.
- Frost resistant
- Reliable measurement
- Maintenance free
- Long lifetime
- Fast response
- Low influence of salinity and pH
- Cost efficient
|Signal output|| - digital (RS485 with UGT-protocol. SDI-12 is available on request)|
- analog (0-1V, other voltage ranges on request)
digital 4 ... 24 VDC (analog 12 ... 24 VDC)182 x 30 x 12 mm
0-60 % vol (0 ... 100 % vol with limited accuracy)
Accuracy with generic calibration
|±3 % vol in mineral soils with average salinity over 0 ... 50 % vol|
Accuracy after specific calibration
|±1 % vol|
0.1 % vol
-40 ... +80 °C (analog -40 ... +60 °C)
extended temperature range on request
|±0.2 °C (analog ±0.8 °C)|
|0.01 °C (analog 0.2 °C)|