The SNiP-SMT is a 'Sensor Node Integrated Package' for LoRaWAN or CAT-M1 communication of real-time soil moisture measurement for continuous soil monitoring. Typical applications taking advantage of IoT SNiPs include irrigation management of orchards, permanent plantings, sporting fields, public gardens and greenhouses.
The SMT-100 measures the dielectric permittivity of a surrounding medium using a proprietary Time Domain Transmission (TDT) technology, using a ring oscillator to produce a frequency of >100MHz, allowing it to operate well even in clayey soils.
Further parameters or additional SMT-100s can be added to the SNiP-SMT, without requiring loggers to match each distinct sensor, substantially reducing the cost of getting a fuller picture on the application. The S-NODE can support an added 5x SMT-100 devices (for a total of 6x SMT-100 sensors).
Time Domain Transmission – SMT-100
The SMT-100 soil moisture probes uses Time Domain Transmission (TDT) technology, combining 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, converting 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. Consequently, it corrects the VSW% value (volumetric soil water) independent of soil type. Maintenance free and frost resistant, the SMT-100 can be used for long-term observations (8+ years continuous).
|Single-Point TDT SNiPs||SNiP-SMT|
|SNiP Measures||VWC % / EC Temperature|
|UOM||VWC % / °C|
|Sensors SNiP Supports||Up to 4 (STD)*|
|*Custom SNiP can support more|
The S-NODE (for Environmental Monitoring) has been designed to support the broad suite of SDI-12 based environmental sensors. The S-NODE can support sensors with higher power requirements; a solar panel can charge either the internal lithium-ion battery or both the node and sensor can be powered by an external 12V system (e.g. battery or mains source).
A decoder suitable for TTN will be provided based upon sensor configuration. See more information on the S-NODE.
The SMT-100 soil moisture probes uses a TDT (Time Domain Transmission) technology. 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 robust design and manufacture, hence can be used for long-term observations (8+ years continuous use).
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. Consequently, it corrects the VSW% value (volumetric soil water) independent of soil type. This is not the case for capacitance sensors.
Higher measurement frequencies are better than lower frequencies. See more details on the SMT-100.
|Signal output||– digital (RS485 with UGT-protocol. SDI-12 is available on request)
– analog (0-1V, other voltage ranges on request)
|Cable length||10 m|
|Power supply||digital 4 to 24 VDC (analog 12 to 24 VDC)|
|Dimensions||182 x 30 x 12 mm|
|Measurement range||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|
|Range||-40 to +80°C (analog -40 to +60°C)
extended temperature range on request
|Accuracy||±0.2°C (analog ±0.8°C)|
|Resolution||0.01°C (analog 0.2°C)|
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