Endress+Hauser Smartec CLD18, Руководство по эксплуатации

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Commissioning Smartec CLD18
30 Hauser
8.4.2 Temperature compensation
The conductivity of a liquid depends heavily on the temperature, as the mobility of the ions
and the number of dissociated molecules are temperature-dependent. In order to compare
measured values, they must be referenced to a defined temperature. The reference
temperature is 25 °C (77 °F).
The temperature is always specified when the conductivity is specified. k(T
0
) represents the
conductivity measured at 25 °C (77 °F) or referenced back to 25 °C (77 °F).
The temperature coefficient α represents the percentage change in the conductivity per degree
of temperature change. The conductivity k at the process temperature is calculated as follows:
k
(T)
k
(T )
0
(1+
=
(T - T ))
0
a
. .
A0009163
Where
k(T) = conductivity at process temperature T
k(T
0
) = conductivity at process temperature T
0
The temperature coefficient depends on both the chemical composition of the solution and on
the temperature, and is between 1 and 5 % per °C. The electrical conductivity of the majority
of diluted saline solutions and natural waters changes in a close-to-linear fashion.
Typical values for the temperature coefficient α:
Natural waters Approx. 2 %/K
Salts (e.g. NaCl) Approx. 2.1 %/K
Alkali (e.g. NaOH) Approx. 1.9 %/K
Acids (e.g. HNO
3
) Approx. 1.3 %/K