Prestored temperature compensation curves, Determining the temperature coefficient, 1 + (t - 25) – YSI 3200 User Manual
Page 52: T - 25)
Principles of Operation
Section 8
temperature coefficient. In extreme cases, the temperature coefficient may have a value as high
as 7%/
°C. Each conductive ion has a different temperature coefficient.
When practical, control the temperature of the solution to be analyzed. For high precision work
(±1%), maintain the temperature at 25
°C ± 0.1°C. For routine lab work, 25°C ± 0.5°C may be
acceptable. (Ref: ASTM D1125-82 Standard Methods of Test for Electrical Conductivity of
Water)
When sample temperature control is not practical, use temperature correction to determine the
conductivity at 25
°C. The temperature coefficient of your sample can be determined either from
published data or from measurements of representative samples. This coefficient may then be
applied to correct future measurements on samples of similar composition. If sample composition
changes appreciably, the coefficient should be redetermined.
Once the temperature coefficient is known, the conductivity at 25
°C can be manually determined
from the following equation:
ℵ
ℵ
25
T
=
1 + (T - 25)
α
where T
= temperature of sample
ℵ25 = conductivity at 25°C
ℵT = conductivity at measurement temperature T
α
= temperature coefficient of the conductivity solution
Prestored Temperature Compensation Curves
The YSI 3200 has two pre-stored non-linear temperature compensation curves, ultrapure water
and natural water. These curves were obtained from the following references:
Ultrapure water:
Conductivity and Resistivity of Water from the Melting to Critical Points,
Truman S. Light and Stuart L. Licht, Analytical Chemistry, 59, 2327.
Natural water:
Water quality - Method for the determination of electrical conductivity,
BS EN 27888 : 1993.
Determining The Temperature Coefficient
You can manually determine the linear temperature correction coefficient of a solution by
measuring its conductivity at different temperatures using the following equation:
α
=
-
(T - 25)
T
25
25
ℵ
ℵ
ℵ
where T
= temperature of sample
ℵ25 = conductivity at 25°C
ℵT
= conductivity at measurement temperature T
α
= temperature coefficient of the conductivity solution
YSI Incorporated
Model 3200
48