
75-1
75.1 Introduction
Previous research showed that the dielectric properties of hygroscopic materials can be used to esti-
mate
th
e
MC pr
esent
in th
ese
ma
terials
(Ne
lson,
19
77;
Kl
ein,
19
81)
. e va
riation
in di
electric
co
n-
stant with MC for shelled yellow eld corn (Figure 75.1) was found to be more pronounced between
1
and
5 MH
z
(Ne
lson,
19
78)
. u
s,
(ε
r1
− ε
r2
), the dierence in the dielectric constants at 1 and 5 MHz
or any other higher frequency, should be a good indicator of the moisture present in the material. e
di
erence
in ca
pacitance
of a pa
rallel-plate
sy
stem
of pl
ate
ar
ea
A an
d
se
paration
d at tw
o
fr
equencies
can be written as
C