NAVI F-52, Инструкция по эксплуатации

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Chapter 16 Reference
16.4 Conductivity measuring
F-52, 53, 54, 55 241
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Measuring conductivity
“Conductivity” is an index that expresses the ease with which electric current flows through a
material. Conductors are categorized either as “electron conductors,” such as metals and other
substances which use free electrons to conduct electricity, or “ion conductors,” such as elec-
trolytic solution or fused salt, which use ions to conduct electricity. This section deals with
the kind of conductivity that pertains to ions, especially the conductivity of electrolytic solu-
tion that uses water as the solvent. As shown in Fig.6, two pole plates with an area A
(expressed in m
2
) are positioned parallel to each other, separated by distance l (expressed in
m), then solution is poured into the cell until full and alternating current is run between the
plates.
Fig.6 Conductivity cell imitative
Each positive and negative ion in the solution will migrate toward the oppositely charged
pole. The result is that current flows through the solution by means of ion conductivity. When
this occurs, resistance R(expressed in
Ω
), is in inverse proportion to the area A (expressed in
m) of the pole plates, as is the case with metal and other conductors, and is proportional to the
distance l (expressed in m) between the two pole plates. These relationships are expressed by
equation 1, below.
R = r
×
l/a = rJ (Equation 1)
R: Resistance(
Ω
)
r: Specific resistance(
Ω ・
m)
a: Pole plate area(m)
l: distance between pole plates(m)
J: Cell constant(m)
Specific resistance (expressed in
Ω⋅
m) is an index that indicates the difficulty with which cur-
rent flows and is a constant determined according to the solution. The inverse of r (expressed
in
Ω⋅
m), which is L (and is equal to 1/r), is called the “specific conductivity” and is widely
used as an index to express the ease with which current flows. Specific conductivity L is gen-
erally referred to as simply “conductivity” and is expressed in units of S/m.
Inserting conductivity L (expressed in S/m) into equation 1 results in equation 2, below.
R = J/L (Equation 2)
As is clear from equation 2, when a conductivity cell having a cell constant J of 1 m is used l
in other words, when a conductivity cell having two pole plates that each have an area A of 1
m and are positioned parallel to each other such that the distance l between the two plates is 1
Solution
Polar plates a m
2
x2