TECHNICAL DATA
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SMARTPAT COND 1200
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Technical data
7.1 Measuring principle
7.1.1 Conductivity measurement
Conductivity is defined as the property of an aqueous solution to conduct electricity by ion
transportation. The higher the ion concentration, the more current can flow. Using Ohm's law
(Resistance = Voltage/Current) the resistance of a liquid can be determined by measuring the
current while keeping voltage constant. Specific conductivity is defined by 1/resistance. The unit
of measurement is Siemens and is normally expressed in
μ
S/cm. An important criterion for the
measuring range of conductivity cells is the geometry of the electrodes.
There are two rules which are characteristic for conductivity measurement:
1. The larger the distance between the two electrodes, the larger the resistance.
2. The larger the electrode surface, the lower the resistance.
The surface area (A) and the distance (L) must be correctly matched to the desired measuring
range. This is called the "cell constant" defined as c=L/A.
Figure 7-1: Measuring principle for conductivity measurement
1
Flow direction
2
Inner electrode
3
Outer electrode
4
Power supply
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