Connecting an Acclima TDR310H to an Arduino-compatible datalogger.
Update: August 5, 2019
We've successfully connected to the sensor using an open source library and retrieved preliminary data. Next steps include:
- Stabilizing the return signal so that measurements are retrieved every X seconds (perhaps this only requires a stable screw terminal connection in lieu of e.g. a breadboard);
- Writing code to return only a single set of measurements at a time (rather than the current code, which runs on a loop)
- Reviewing the voltage signal level output by the sensor
From the TDR310H Data Sheet (in this repo and online):
From the TDR310H Data Sheet (in this repo and online):
From the Installation Manual (in this repo and online):
We'll use the EnviroDIY SDI-12 Library, installed on an Adafruit Feather M0. We'll power the sensor (which requires at least 3.5 volts) with the USB pin (5V).
Note: not sure if the signal data is 3.3 volts or 5 volts, need to check.
Using the d_simple_logger.ino example from the library; simply modify the "DATA_PIN" variable to pin 6 on line 78:
#define DATA_PIN 6 // The pin of the SDI-12 data bus
This code should print values out to the serial port. The suitably modified code is here).
We'll test the setup in a beaker of water:
Initial connection to the device worked within a few seconds. For some reason, the sensor output data with stochastic time intervals between measurements. This may have been due to poor wiring connections on the breaboard.
You can see the 5 reported sensor values in the above printout:
0.0,25.1,1.1,0,0
Corresponding to:
Volumetric Water Content, Soil Temperature, Bulk Relative Permittivity, Soil Electric Conductivity, Soil Pore Water EC
Before the probe is placed in water, the only non-zero values are for the temperature (25.1 C), and the Bulk Relative Permittivity (1.1).
We then readjusted the wires slightly, and performed a test in which the probe was dipped into the beaker in stages, with more of the prongs wetted over time; it was then removed, and then returned to the beaker. The values changed as expected, and were reported more consistently (every 10 seconds or so):
