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 base SNiP-SMT integrates 1x S-NODE and 1x SMT-100 soil moisture sensor to a site’s unique network, communication and power requirements.
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.
See Further Specifications on the S-NODE
See Further Specifications on the SMT-100 Sensor
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 |
Core Sensor/Device (Single-Point) |
SMT-100 |
UOM | VWC % / °C |
SNiP Node | S-NODE |
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.
Advantages
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 |
Moisture | |
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 |
Resolution | 0.1% vol |
Temperature | |
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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