Wiki source code of 5TM

Last modified by Michael Sibayan on 2022/05/03 16:48
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1 = Overview =
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3 [[Decagon 5TM (Manufacturers webpage)>>url:http://www.decagon.com/products/soils/volumetric-water-content-sensors/5tm-vwc-temp/||rel="__blank"]]
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6 This sensor communicates digitally via the SDI-12 protocol. [[**http:~~/~~/www.sdi-12.org/**>>url:http://www.sdi-12.org/]]
7 The cRIO in Panel 02 contains an NI-9403 high speed digital I/O module. The FPGA on the cRIO is programmed with a custom SDI-12 communications emulator. The module is capable of communicating with approximately 26 of the 32 digital buses simultaneously, this limit is aparently a hardware issue related to the impedance of the SDI-12 sensor network (basically the current draw to communicate with all those sensors is more than the module can provide). To combat this problem, the SDI-12 network is polled in two parts - all 5TM sensors, then all MPS-2 sensors.
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9 The digital signal, when decoded, forms a simple ASCII text string which identifies the sensor address, the relative permittivity, and the temperature in degrees Celsius. An example output string is "B+7.5+25.6" - this shows sensor address "B", relative permittivity "+7.5", and temperature "25.6" Celsius.
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12 The 5TM terminates to a [[custom junction board designed by Aztera>>doc:AzteraBOB]] (http:~/~/www.aztera.com/). The board provides a many-to-one junction for power, ground, and signal buses which allows for 32 SDI-12 sensors to be connected to a single signal bus.
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14 = Calculation Notes =
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16 {{display reference="5TM_CalculationNotes"/}}
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18 = Wiring Diagram =
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20 [[image:5TM_Wiring_Schematic.png||style="display: block; margin-left: auto; margin-right: auto; width="]]
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