Hanna Instruments HI 98188 - Manual (Page 11)

11
From practical reasons, the salinity of a solution is derived from the salinity of
the seawater. Two methods of calculating the salinity from the conductivity are
suported:
• Natural seawater scale
• Practical salinity scale
Natural sea water scale (UNESCO 1966)
According to the definition, salinity of a sample in ppt is calculated using the
following formula:
where:
R
T
- coefficient;
C
T
(sample) - uncompensated conductivity at T °C;
C(35;15)= 42914
m
S/cm - the corresponding conductivity of KCl solution
containing a mass of 32.4356 g KCl / 1 Kg solution;
r
T
- temperature compensation polynom.
Note: The formula can be applied for temperatures between 10 °C and 31 °C.
To access this range press Mode while in Salinity range until the sea water
scale [SW] is displayed.
Practical salinity scale
This is a practical scale based on the precise measurement of the electrical
conductivity of a range of solution of known salinity.
The relationship derived from the scale relate salinity, conductivity, tempera-
ture and pressure and use a solution with a salinity of 35 ‰ as datum point.
This is taken to have a conductivity of 42.914 % mS/cm of 15 °C and
atmospheric pressure.