calibrate the probe accordingly. The calibration curves will mathematically have the appearance
of equation [2.1] or [2.2]
θ
= A + B
E
r
+ C
E
r
2
+D
E
r
3
[2.1]
θ
= A
E
r
1/2
+ B
[2.2]
Where
θ
is moisture
E
r
is the real dielectric permittivity and A,B,C, and D are coefficients. If
the user wishes to use the Hydra Probe to measure moisture in a matrix that is not mineral soil,
the user must empirically and experimentally solve equation [2.1] or equation [2.2]. Also, The
user should review the matrix compatibility requirements of the probe in section 3.1.
2.3.1 Frozen Soil
The Hydra Probe can also be used to determine if soil is frozen. Once ice reaches 0
o
Celsius, it
will begin to thaw and the real dielectric permittivity will increase from 5. The temperature alone
may not indicate whether or not the soil is frozen. As the soil begins to thaw, the soil moisture
and the real dielectric permittivity should return to values similar to what they were before the
soil froze.
14
