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Description: The SparkFun Soil Moisture Sensor is a simple breakout for measuring the moisture in soil and similar materials. The soil moisture sensor is pretty straightforward to use. The two large, exposed pads function as probes for the sensor, together acting as a variable resistor. The more water that is in the soil means the better the conductivity between the pads will be, resulting in a lower resistance and a higher SIG out. This version of the Soil Moisture Sensor includes a 3-pin screw pin terminal pre-soldered to the board for easy wiring and setup.

To get the SparkFun Soil Moisture Sensor functioning, all you will need is to connect the VCC and GND pins to your Arduino-based device (or compatible development board). You will receive a SIG out, which will depend on the amount of water in the soil. One commonly known issue with soil moisture senors is their short lifespan when exposed to a moist environment. To combat this, we’ve had the PCB coated in gold finishing (ENIG, or Electroless Nickel Immersion Gold).

Note: Check the Hookup Guide below for assembly and weatherproofing instructions, as well as a simple example project that you can put together yourself!

Get Started with the Soil Moisture Sensor Guide

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Customer Comments

  • Wouldnt this device with its current over the terminals make the water sour?

    • By sour do you mean does the electricity alter the pH of the water? This probe acts as a voltage divider, so there is no current flowing across the probes, only through them. The probe itself should not be a problem. The gold and copper are fine for the plant, and the fiberglass is inert. Leaving the device on all the time can corrode the exposed PCB probes. However, it is suggested in the Hookup Guide that you not leave the probe on all the time and only power it when you want to take a measurement. This same method should result in the current flow not having any affect on the water composition. And even if it did, it shouldn’t be enough to affect the plant’s health as water would be replenished frequently enough to negate any side effects.

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