Wireless Soil Moisture Sensor • PS-3228

The Wireless Soil Moisture Sensor measures the volumetric water content (%VWC) of soil, reporting data in real time or storing it onboard the sensor's memory for long-term experiments. Durable and easy to use, the Wireless Soil Moisture Sensor is the perfect tool for monitoring controlled experiments in the classroom and long-term experiments outdoors. From experiments in evaporation and soil composition to water consumption and plant competition, the Wireless Soil Moisture Sensor makes it easy for students to investigate a wide array of topics both inside and outside of the classroom.

To use the sensor, dig a trench a few inches below the ground's surface and place the sensor's spear-shaped portion in the soil. Be sure to pack the soil tightly around the sensor for best accuracy. After use, the surrounding soil should be loosened to reduce the risk of damaging the sensor's cord.

How It Works

The Wireless Soil Moisture Sensor determines the percent water content by volume of soil by measuring the dielectric constant of the space around the blade-shaped capacitor. An electric field generated by the sensor responds to the capacitance of the surrounding space and uses the response to calculate the soil's percent water content per volume.

Liquid water has a uniquely high capacitance, making it the predominant contributor to the sensor's measurement. The sensor comes factory-calibrated for soils with discreet values of volumetric water content and outputs readings in percentage of total space filled. Accurate readings range from 0%, in which there is little to no moisture in a dried sample, to 45%, in which all the available pore space within the soil is saturated with water. For a % saturation reading, divide the value by 45.

The sensor has been calibrated to support analyses in 3 of the predominant soil types: sandy soils, clay soils, and loamy soils. If you are unsure of your soil type, select the intermediate calibration, loamy soil which works for the broadest conditions.