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8.3.1 Installing the Sensor
When selecting a site for installation, it is important to remember that the soil adjacent to the probe
surface has the strongest influence on the probe reading and that the probe measures the volumetric
water content. Therefore any air gaps or excessive soil compaction around the probe can profoundly
influence the readings. Also, do not install the probes adjacent to large metal objects such as metal
poles or stakes. This can attenuate the probe's electromagnetic field and adversely affect output
readings. Since the sensor has gaps between its prongs, it is also important to consider the size of
the media you are inserting the probe into. It is possible to get sticks, bark, roots or other material stuck
between the probe prongs, which will adversely affect readings. Finally, be careful when inserting the
probes into dense soil, as the prongs will break if excessive sideways force is used when pushing them
in.
You can safely connect up to 200 feet without signal attenuation. For most applications, you will want
to seal the connections from the elements to maintain a good connection and to prevent corrosion.
Insert the probes into the soil, making sure that the prongs are buried completely up to the black
overmolding. The tip of each prong has been sharpened to make it easier to push the probe in. The
probe may be difficult to insert into extremely compact or dry soil. If you have difficulty inserting the
probe, try loosening the soil somewhat or wetting the soil. Never pound it in! The probe can be
oriented in any direction. However, orienting the flat side perpendicular to the surface of the soil
will minimize effects on downward water movement.
When removing the probe from the soil, do not pull it out of the soil by the cable! Doing so may
break internal connections and make the probe unusable.
8.3.2 How does the soil water content sensor work?
The soil water content sensor measures the dielectric constant of the soil in order to find its
volumetric water content. Since the dielectric constant of water is much higher than that of air or soil
minerals, the dielectric constant of the soil is a sensitive measure of water content. The sensor's
two-prong design and higher measurement frequency allows the EC-5 to measure VWC from 0 to
100%, and allows accurate measurement of all soil types and a much wider range of salinities.
Doc. # 7430-0710-01 Rev. C
Sensor probe
Figure 8-4. eS1110 soil water content sensor
Switchcraft
connector
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