Profiling Soil Moisture Probes with Integrated LoRaWAN Module



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The “Lo” series of Otto soil moisture probes offer a built in LoRaWAN communications board, allowing them to be used with any LoRaWAN system. Simply configure the probe using the TBS12 GUI and set the LoRaWAN communications parameters, start the probe running and away you go. Power for the units comes from  a 2.5 AH lithium thionyl battery which in most applications will give a season’s life between changes.


Where to Use It


The Otto-LO is intended for use in seasonal crops, where a fresh battery can be installed with each planting.
Because the radio antenna is integrated in to the head of the probe, it sits just aboveground level, which means that the range will be shorter than if the antenna were mounted higher (e.g 2m above ground level). For this reason you should limit use of the device to small farms (less than 1 to 2 km from the base station / Gateway.
Overall battery life will also depend on how often the probe reads and sends its values: setting these rates to hourly will give a much longer life than at 15 minute intervals.
If you require frequent logging, long range and long or unlimited batter life, then look at the TBS12B or TBS12S which can be used with the Otto soil moisture probe or any other SDI-12 compatible sensors.


Flexible Configuration


The probes may be built in lengths of 30cm to 200cm and can be fitted with from 2 to 15 sensors. The sensor elements can be installed at 10cm increments along the probe body and, to save cost, depths can be skipped by inserting spacer boards of 10, 20 or 30cm length. Common configurations are 30cm 3 sensor, 50cm 5 sensor, 100cm 6 sensor and 100cm 10 sensor.
The Otto-Lo sensor elements are different from the standard Otto sensor cells in that they are designed to run from a 3.3V power supply - the standard cells run on 12V in order to be fully compatible with the SDI-12 protocol. Running the Otto-LO cells on 3.3V reduces power consumption and hence maximise battery life.




The Otto  sensors come with a default air-water calibration and users can select  generic soil calibrations for sand, potting mix and clay. Users can perform their own soil specific calibration and save the obtained calibration coefficients on to  the probe. The Otto probes are the first capacitance probe to include soil temperature compensation: allowing users to remove the changes in indicated moisture caused by variations in the dielectric properties of the soil with temperature.


Re-Enterable Above Ground Probe


The Otto-Lo  probes are completely user configurable - users can add or remove sensors at any time. This gives installers the flexibility to shorten a probe if they hit a rock layer or to adjust sensor positions to match the soil profile. Being re-enterable the sensors can be serviced and any faulty components replaced

If you want to use the sealed versions of the Otto probe in a LoRaWAN environment, then simply connect the probe to the TBS12 B or TBS12S module..


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