
4
OPERATION
View a visual demonstration on proper installation of the sensor in How to install soil
moisture sensors.
The sensor 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. The sensor
measures the average VWC along its length, so a vertical installation will integrate VWC over
a 10-cm depth while a horizontal orientation will measure VWC at a more discrete depth.
The 5TE sensor makes EC measurements by exciting one screw on the sensor and measuring
the current that moves from that screw to the adjacent grounded screw. The distance
between the screws is an important part of the EC calculation. If 5TE sensors are placed
close together (within 20 cm), it is possible for some of the current that leaves the excited
screw to pass through the nearby sensor ground screw, thus producing an erroneous
sensor reading.
This problem occurs regardless of which logging system is being used if the ground wires
are connected at all times. If sensors must be close together (e.g., column experiments),
consider a multiplexing option that would isolate the ground wires.
If installing sensors vertically at short depth intervals, do not bury them directly over the top
of each other. Although at times the vertical distance may be less than 20 cm, the sensors
can be staggered horizontally so they are not directly above each other, thus meeting the
distance requirement.
2.2 REMOVING THE SENSOR
When removing the sensor from the soil, do not pull it out of the soil by the cable! Doing so
may break internal connections and make the sensor unusable.
2.3 CONNECTING
The 5TE works seamlessly with METER data loggers. The 5TE can also be used with other
data loggers, such as those from Campbell Scientific, Inc. For extensive directions on how to
integrate the sensors into third-party loggers, refer to the 5TE Integrator Guide.
5TE sensors require an excitation voltage in the range of 3.6 to 15 VDC. 5TE can be integrated
using DDI serial or SDI-12 protocol. See the 5TE Integrator Guide for details on interfacing
with data acquisition systems.
The 5TE sensors come with a 3.5-mm stereo plug connector (Figure2) to facilitate easy
connection with METER loggers. 5TE sensors may be ordered with stripped and tinned wires
to facilitate connecting to some third-party loggers (Section2.3.2).