5TE Operator’s Manual
3. Theory
6
3. Theory
Volumetric Water Content
The 5TE probe uses an electromagnetic field to measure the
dielectric permittivity of the surrounding medium. The probe
supplies a 70 MHz oscillating wave to the probe prongs that
charges according to the dielectric of the material. The stored
charge is proportional to soil dielectric and soil volumetric
water content. The 5TE microprocessor measures the charge
and outputs a value of dielectric permittivity from the probe.
Temperature
The 5TE uses a surface-mounted thermistor to take tempera-
ture readings. It is located underneath the probe overmold,
next to one of the prongs, and will read the temperature of the
prong surface. The 5TE will output temperature in °C unless
otherwise stated in your preferences file in either the ECH
2
O
DataTrac or ECH
2
O Utility programs.
It is important to note that if the black plastic overmold of the
probe is in direct sunshine, the temperature measurement may
read high. Exposure of the overmold to solar radiation will
also drastically decrease the life expectancy of the sensor. We
do not recommend that the sensor be installed with the over-
mold in the sun.
