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H87.0.0X.6C-01
Operating manual G 7500 Series
page 15 of 34
6.2 Basics about conductivity
Definition of conductivity
:
The ability of a material to conduct electric current:
𝛾 =
𝑙
𝑅•𝐴
l
:
length of the material
A
:
diameter
R
:
measured resistance
Unit
[𝛾] =
𝑆𝑖𝑒𝑚𝑒𝑛𝑠
𝑀𝑒𝑡𝑒𝑟
=
𝑆
𝑚
, common for liquids:
𝑚𝑆
𝑐𝑚
and
µ𝑆
𝑐𝑚
The conductivity is the reciprocal value of the resistivity.
(The conductance is the reciprocal value of the measured resistance R)
6.3 Conductivity measurement
The conductivity measurement is a rather uncomplicated measurement. The
standard measuring cells are stable for a long time if used correctly and can be
adjusted by slope correction.
Range
1
2
3
4
45..500 mS/cm 5.0..50.0
mS/cm
500..5000
µS/cm
0.0..500.0
µS/cm
Within the integrated automatic range selection, the range with the best resolution is
automatically selected.
6.4 Electrodes / measuring cells
6.4.1 Design and selection
Basically there are two types of measuring cells: 2-pole and 4-pole cells. The
operation is done similarly; the 4-pole measuring cells can compensate polarization
effects and
– up to some degree – soiling due to its complex measuring method.
2-pole measuring cell
4-pole measuring cell
6.4.2 Calibration / Adjustment of measuring cells
Especially in harsh environments and over long time the cell constants of measuring
cells are drifting. Depending on the application and usage we recommend a regular
checking of the precision of the measuring chain: inst cell. For this there are
control solutions available (GKL 100, 101, 102). At normal usage a checking each
half year is recommended.