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7 .4 Temperature compensation
The conductivity of aqueous solutions is temperature dependent. The conductivity of a solution can
be calculated back to a standard reference temperature by means of temperature compensation.
Commonly used reference temperatures for comparing conductivities are 25°C and 20°C. If the
measurement is carried out at a set reference temperature, no temperature compensation is required.
7 .4 .1 Non-linear temperature compensation according to EN 27888
For most applications, for example in the field of fish breeding and the measurement of surface
and drinking water, the non-linear temperature compensation for natural water is sufficiently
accurate. The usual reference temperature is 25 °C.
Recommended conductivity range for non-linear temperature compensation: 60 to 1000 µS/cm
7 .4 .2 Linear temperature compensation and determination of the temperature
coefficient
If the temperature compensation function is not known, linear temperature compensation
is used in practice. In this case, it is assumed that the temperature dependence over the
solution's observed concentration range is about the same.
The conversion of electrical conductivity (EC) to the reference temperature can be carried out
using the following equation:
•
TC
= Temperature coefficient
Lin
•
EC
= Conductivity at the set reference temperature
Tref
•
EC
= Conductivity at measuring temperature X
TX
•
T
= Reference temperature (25°C / 20°C)
ref
•
T
= Temperature of the measuring solution
X
The temperature coefficient can be determined by measuring the conductivity of a solution
without temperature compensation at two temperatures, T1 and T2.
7 .5 Maintenance and storage of conductivity electrodes
Conductivity measuring cells can be stored dry. It is recommended to rinse the electrodes
properly with distilled or deionized water after each measurement and then dry them with
a fine paper towel to avoid deposits. In the event of coarse contamination, the electrodes
can be cleaned with a soft brush.
SD_335_1 10/2020
EC
EC
=
TX
Tref
1+ TK
lin
(100 %)
= (EC
- EC
) * 100 %
TC
T1
T2
Lin
(T1- T2) * EC
* (T
-T
)
x
ref
T1
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