Chauvin Arnoux C 320 Notice De Fonctionnement page 32

English
γ
= 1 / ρ ; 1 S.cm-1 = 1 (Ω.cm)-1
Just as the resistance and the resistivity are related by the formula: R = ρ (I / S)
The conductance and the conductivity are related by the formula: G =
Where
G conductance in Siemens
γ
conductivity in S.cm-1.
S area in cm2.
I length in cm.
The conductivity of an electrolyte can be measured simply by maintaining a fixed
alternating voltage on the terminals of the cell and measuring the current that
flows through it.
Characteristics of the measurement cell:
The conductometry cell comprises two square plates (5mm on a side) of platinum-
plated platinum, plane, parallel, and 4mm apart. The smooth platinum plates are
platinum-plated, in other words covered with platinum dendrites to form a large
porous surface area. The purpose of this operation is to limit polarization of the
electrodes.
The measured conductance of an electrolytic solution depends not only on the
conductivity of the volume of solution exactly between the plates of the sensor,
but also on the solution near this cubic volume, because the measurement cell is
immersed in a larger volume of solution.
Calibrating the measurement system:
In practice, the « cell constant » of the measurement line can be determined only
by calibration, by immersing the cell used in a standard solution having a known
conductivity at a given temperature. (see page 39).
32
γ
(S / I)
Conductimeter C 320