49
IM 12D06D05-01E
A
APPENDICES
B. Calculation of temperature coefficient factor
(with two known conductivity values at different temperatures)
Measure the conductivity of the liquid at two temperatures, one below the reference and above
thereferencetemperaturewiththetemperaturecoefficientsetto0,00%/°Candusethefollowing
equationtocalculateatemperaturecoefficient(α).
T
K
ref
=
1+α ( T - T
ref
)
K
2
- K
1
α
=
K
1
( T
2
- T
ref
) - K
2
( T
1
- T
ref
)
K
1
K
2
K
ref
=
=
1+α ( T
1
- T
ref
)
1+α ( T
2
- T
ref
)
K
1
(1 + α ( T
2
- T
ref
)) = K
2
(1 + α ( T
1
- T
ref
))
K
1
+ α ( T
2
- T
ref
) - K
2
+ α ( T
1
- T
ref
) = K
2
- K
1
Where T
1
, T
2
:liquidtemperature(°C)
K
1
: conductivity at T
1
(°C)
K
2
: conductivity at T
2
(°C)
Figure 11-1. Conductivity
Calculation example
Calculate the temperature co-efficient of a liquid from the following data.
Conductivity124.5µS/cmataliquidtemperatureof18.0°Canda
conductivity147.6µS/cmataliquidtemperatureof31.0°C.
Substitutingthedataintheaboveformulagivesthefollowingresult.
x 100= 1.298 %/C
α =
124.5(31.0 - 25) - 147.6(18.0 - 25)
SetthetemperaturecoefficientintheISC450Gconverter.