inconsistent Results

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This topic contains 8 replies, has 3 voices, and was last updated by Profile photo of lilcano lilcano 3 months, 2 weeks ago.

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  • #2164
    Profile photo of lilcano
    lilcano
    Participant

    Hello,
    so i am using the SDI-12 library at https://github.com/EnviroDIY/Arduino-SDI-12.git to collect Ea and VWC data from the decagon 5TM sensors attached to an arduino Uno R3. Using the attached sketch, unfortunately the results obtained are inconsistent after several days of data collections. as shown in the plot of the different data points. has any one observed similar results? Or what am i doing wrong in the sketch? Please help

  • #2169
    Profile photo of Shannon Hicks
    Shannon Hicks
    Keymaster

    It would be helpful for you to attach a jpg of png image of your graph instead of a Powerpoint slide. You also can’t attach the raw .ino file to forum posts, but you can cut and paste it using the “code” tags in the post editor tools.

    And on your graph, can you please label both the x and y-axis? I don’t know what parameter you’re graphing and on what time scale your measurements covered. I’m assuming your graph shows either temperature or soil moisture. How were you testing the sensor? Was is installed outside or in a controlled environment? What kind of results were you expecting and what makes you think something is inconsistent?

  • #2172
    Profile photo of lilcano
    lilcano
    Participant

    Hello,
    Thanks for the quick response.Bellow is the sketch running on the arduino Uno R3. The devices where actually tested on the field(not in a controlled environment).The results shown on the plot is VMC collected every minute from the sensors. Actually the VWC is expected to reduce with time, these results are collected over a period of 3 days. Surprisingly they show a sinusoidal curve and the sensors are places in a sandy loam soil. I am thinking maybe the sketch has some problem. Please do you have any ideas why such results?

    Attachments:
  • #2174
    Profile photo of Shannon Hicks
    Shannon Hicks
    Keymaster

    The graph looks more like a plot of temperature rather than VWC. Are you sure you’re plotting the right column of data? What are you using to actually record the data? Your sketch doesn’t output the data to a file or even print it in a easily-captured string out to the serial port, so I’m wondering how you collected multiple days of data. Plot your other variable and see what it looks like. The code also shows that you’re using 2 sensors. What does the data from the second sensor look like? The easiest way to see if a probe is working properly is to install 2 of them in the same location and in the same media and see if you get similar results for both of them.

  • #2177
    Profile photo of lilcano
    lilcano
    Participant

    Hello,

    I just checked again and yes i am plotting the VWC. As for the collection of the data i am actually using an SD card shield on the arduino to store the data. As you can see from the image there are two curves each one for the different sensors placed at the same location. After getting this results i decided to take out the SD card shield and run the attach sketch with the arduino connected to my computer and unfortunately i obtain similar results on the arduino IDE serial monitor. please any ideas?

  • #2178
    Profile photo of Sara Damiano
    Sara Damiano
    Participant

    Please, like Shannon suggested, copy in your actual code using the “Add Code Snippet” button and actually attach your raw data, not a picture of it. Also, like Shannon said, please plot your EA and temperature to see how they look. And, again, like Shannon said, explain:

    How were you testing the sensor? Was is installed outside or in a controlled environment? What kind of results were you expecting and what makes you think something is inconsistent?

  • #2179
    Profile photo of lilcano
    lilcano
    Participant

    Hello Sara,

    Thanks for the reply, attached is a copy of the actual raw data and the sensor and arduino are actually places in a field(so not a controlled environment). I was expecting the VWC to reduce with time and not the sinusoidal behavior, Equally the Ea will give similar curve because its used to calculate the VWC using the Topps equation. Please can you take a look at the attached raw data and advice?

    Attachments:
    1. LOGGER11.csv
  • #2181
    Profile photo of Shannon Hicks
    Shannon Hicks
    Keymaster

    I plotted the temperature and VWC on the same chart and you can see that they are very much linked together. Can you answer whether the sensor is completely buried in the soil, and if so how deep is it? If only the fiberglass tines are inserted into the soil but the rest of the sensor body is above ground and subjected to direct sunlight or drastic temperature swings, then I would assume that’s what causing the issue.

    Can you also post the actual sketch you used on your Arduino board to capture your data and write it to the memory card. I can also show you how to record more significant digits for the VWC parameter so that you get finer resolution and a smoother curve. But I need you to post the actual sketch you used for the logger. And tell us exactly how the sensor was installed in the ground. Can you repeat this experiment indoors where the temperature is constant and in a pot of soil or somewhere where you can purposely vary the moisture content?

    Attachments:
    • #2191
      Profile photo of lilcano
      lilcano
      Participant

      Hello Hicks,

      Thanks for the reply, the sensors are buried completely in the soil as for the length i did not really measure that. Please see the attached file for the complete sketch running on the Arduino, and let me know what you think.

      Thanks

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