Someone can help to measure with a watermark moisture sensor

  • Good day.

    Since a couple of day, I am trying to use a watermark sensor without bug success.
    I got servreal documentation
    First I found good information on
    SMX datasheet
    read paragraph 2 and 3.
    I also look at this article and I worked on the schema b) under the title "Reading the Watermark 200SS Sensors".
    Voltage divider
    Unfortunately, I can not get a reliable value.

    I also found this good schema alt text.

    Finally, I also found this another alaterative

    Which look nice but apparently there is a condensator in a bad sens.

    I spent about four days, trying with Voltage divider.
    I specially follow this tutorial, But I never got a correct value and I do not know if I am doing something else wrong or if I missed a detail.
    I have two new Watermark. One is wet and the second is fully dry. I also have a WATERMRK digital reader and when I measure it with the reader, I got the value 199 for the dry sensor, and 0 for the wet sensor.

    When I take the measure with my Adafruit Trinket Pro by alernating the polartity 10 time, I never get a value similar to the digital reader. The value are close 300 and more.

    Now I am going to try the second schema, but as I sepnd so many time on this issue, I would like to know if some one as a good expertise with WATERMAK and adafruit or arduino board and how you develop you schetch t measure a Soil Water potetial in Kpa?

    If you develop a such sensor with Arduino or adafruit, sharing your experience (Any links, exemple, titorial, recommandation), will help a lot.!

    Many thank

  • This post is deleted!

  • Hi there! Reading the Watermark sensor is no easy task indeed. Took us a while to get accurate and reliable data out of these sensors.

    First of all, take a look at the official documentation provided by Irrometer:
    Especially the pseudo-AC excitation is very important and make sure you calibrate the readings using the soil temperature.

    There's quite some off-the-shelf hardware on the market already. Look for a device that has a low power consumption so you can measure throughout the year, for example:

    Let me know if you have any more questions!

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