H72.0.01.6C-02
Operating Manual GMH 3431
page 8 of 14
_____________________________________________________
_____________________________________________________________________________
The salinity measurement has its “own” temperature compensation, i.e. the temperature is automatically
taken into account for the salinity measurement. The menu settings regarding the temperature compensation
are ignored.
Attention:
The salt composition of the different seas is not the identical. Depending on place,
weather, tides, etc. there may be considerable divergences to the 35 ‰ according to IOT.
Additionally the salt composition may influence the ratio between salinity and actual salt content.
6.6 Electrodes / measuring cells
6.6.1 Design
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
6.7 Temperature compensation
The conductivity of aqueous solutions depends on its temperature. The temperature dependency is strongly
dependent on the type of solution. The temperature compensation recalculates solutions’ conductivity to a
consistent reference temperature. The most common reference temperature is 25 °C.
6.7.1 Temperature compensation “nLF” according to EN 27888
For most applications (e.g. in the area of fish farming, surface or drinking water measurements, etc.) the non-
linear temperature compensation for natural water (“nLF”, according to EN 27888) is sufficiently accurate.
The common reference temperature is 25 °C.
Recommended application range of nLF-compensation: between 60 µS/cm and 1000 µS/cm.
6.7.2 Linear temperature compensation and determination of temperature coefficient “t.Lin“
If the actual function needed for exact temperature compensation is not known, “linear temperature
compensation” is normally selected (Menu, t.Cor = Lin, t.Lin corresponds
TK
), i.e. one assumes that the
actual temperature dependency at the considered concentration range is approximately equal:
LF
LF
1
TK
100% • Tx
Tref
Temperature coefficient of about 2.0 %/K are most common.
A temperature coefficient can be determined for example by measuring a solution with deactivated
temperature compensation at two different temperatures (T1 and T2).
TK
LF
LF
• 100%
T1
T2 • LF
TK
lin
is the value input at the menu “t.Lin”.
LF
T1
conductivity at temperature T1
LF
T2
conductivity at temperature T2
