Volumetric water content and dielectric constant from METER group/Decagon 10HS sensor

If you are measuring volumetric water content of soil with an analog sensor such as the METER group (formally Decagon) 10HS sensor, you need to convert the voltage you read from it into either VWC or dielectric constant. The manual of the sensor gives you the conversion formula. In the following video, I demonstrated how to apply the conversion formula to an analog reading:

Even if you are using an SDI-12 sensor, its output may be dielectric constant instead of VWC, which needs conversion using a similar formula. I would do the conversion post data logging since I could potentially find a more precise calibration curve of my soil instead of using their standard mineral soil curve or potting soil curve. Without applying the curve, I can easily apply a different curve.

4 Responses to Volumetric water content and dielectric constant from METER group/Decagon 10HS sensor

  1. Andy Watson says:

    I have some SDI-12 sensors that require 9v or 12v to power them, will they work with your SDI-12 interface board?

    • liudr says:

      If you’re deploying your loggers with 12V rechargeable batteries and solar panels, you can pass 12V to the external power connector to my adapter and move the power jumper to external so the sensors will receive power from the battery. All SDI-12 sensors can work with 12V power, even if they work alright with 5V or 9V. The specification requires an SDI-12 sensor to work between 9.6V and 16V on the “12V” power line although some sensors work fine with 5V (USB etc.) or 9V (9V battery).

      • Andy Watson says:

        okay, but if the sensor is powered at 12 volts, won’t they blow up something on your board’s data wire connection since I’m guessing your board data levels are at 3 volts? Thanks.

  2. liudr says:

    An SDI-12 sensor is expected to take power that is 9.6-16V and must be able to drive data line at 3.5-5.5V. My adapter is able to read such data line voltage level. Data and power are not at the same voltage level.

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